1597132860

# Amazon Interview Experience for SDE-1 | Amazon-WOW 2020

Amazon has a special program called AmazonWOW for women. It is to promote women in technology. It is a very good opportunity for women as they have to only compete with other females, not with males. The online application came in April. The program consists of a two-month internship for prefinal year student and fulltime plus Internship for final year student.

It consisted of a total 4 rounds, first was an online coding contest and then 3 telephonic interviews.

**Online test : **

The first round was an online coding round. It consisted of 2 coding questions and 28 MCQ. We had 1.2 hrs. The coding questions were quite simple but MCQs were very difficult. I would like to say that luck matters a lot in cracking online coding round.

1. First question: Find the longest common subsequence between two string. It is standard Dynamic programming question but the constraints were not very high so I solved it using recursion.

**2. Second question: **I did not find the exact question on any platform but it was very simple. You are given a string consisting of lowercase English alphabets, return the internet resource address of the string.

Internet resource address of a string is defined as

://.ru[/]

can be either http or ftp.

is a string consisting of lower case English alphabtes.

is a non mepty string of lower case English alphabtes.

Ex : httpsunrux -> http://sun.ru/x

For MCQs, you must have a strong grip on OOP and c++ language.:

**Round 1: **

For this round, I was given an amazon chime link and live code editor link in which I had to code. The interviewer started by asking me my introduction and then he gave his introduction. In my introduction, I told him about my passion for competitive coding, writing and reading.

Then Immediately we moved to coding questions. He told me that I have only 45 minutes to answer so I have to come up with the best approach possible.

1. First Question: Find x ^ y mod z. I gave him the O(log(y)) approach. I covered all the edge cases when x will be zero or negative when y will be zero or negative. When y will be negative, he told me to return an error to the user. I coded properly using indentation and suitable variable and function names. I used int to store the variable but when the value is very high I should use long long int. I missed this case. He then moved to the second question.

2. Second Question:  Given a set of dependencies I have to find one of the suitable ordering of the dependencies. I told him I will use topological sort for this. He told me to explain my approach and then I coded it. But while coding I missed an edge case when there will cycle in the dependency. He told me to correct my code. I corrected my code by checking if there is a cycle present in the dependency.

3. Third Question:  For this question, I gave him two-approaches, first one was linearly counting the no of x and second was using a modified binary search. He did not ask me to code this question.

The best part was that I had already solved all these questions before so I did not get nervous there. In the end, I asked him where I can improve, He told me to check code before finally submitting to the interviewer.

After 12 days the result of this round was declared.

**Round 2: **

For this round also, I was provided with the Amazon chime link and live code link. The interviewer asked me two questions.

1.** First Question:**  Add all greater values to every node in a given BST. I gave him O(n ) time complexity solution. Initially, I had written the wrong code but my approach was right. He dry ran my code, pointed out the mistake that I made in code and told me to correct the code. I corrected the code and he was satisfied by my approach. I told him about the time complexity ie O(n). I told him if we consider internal stack then space complexity will o(n) because in the worst case the height of BST can be O(n) if it is skewed BST.

**2. Second Question: ** But in this question, He gave me three conditions.

1. You can traverse the data structure in only one direction.

2. You cannot use extra space ie in-place algorithm.

3. You can use any data structure of your choice.

My first approach was to use an array data structure. I told him that in first traversal I will find the count of negative numbers and then I will start filling my result array. But he said I cannot use extra space.

My second approach was to use a binary search tree and the result will be inorder traversal of the tree. But he told me that I have to return the data structure which I am using.

Then He asked me what are the data structure that I know. I told him I know heap, queue, stack, singly-Linked list and doubly linked list. Then suddenly doubly-linkedList came to my mind and I told him I will use doubly LinkedList. He told me that in doubly-linked you can traverse in both directions. Then I told him that will use a singly linked list. He told me to write code and dry ran my code. He was satisfied with my code.

My second interviewer was a very helpful and knowledgeable person. In the end, he said “it was nice to interview you. ”

After 11 days the second-round result was declared.

**Round 3: **

For this round also, I was provided with the amazon chime link and live code link. The interviewer was a very nice and chill person. He tried to make me comfortable. He introduced himself and then I gave my brief introduction. In this round, I was asked two questions. One was a coding question and the other was OS( operating System ) question.

1. First question:  If we have a well-optimised code, On what factors the maximum no of threads in a process depends?

We had around half an hour discussion on this topic. I told him how threads are used in the client-server application, use of threads in a text editor which simultaneously performs writing, auto-correction and suggestions. He asked me if a site has 1 million clients, then 1 million threads will be created, I told him about the use of multiple servers. I told him the no. thread depends upon the resources of the machine. I told him it will depend upon the memory of the computer. Then He wanted to know, which memory affect it, primary memory or secondary memory. I told primary memory will affect the no of threads as all the processes/ threads reside in the primary memory. I was thinking of other factors also but then he moved to coding question.

After this, we moved to coding question.

**2. Second Question: **  Find the first missing positive number in an array.

My first approach was to use hashing, the time complexity of this approach was O(n ) and the space complexity was O(n). He told me to do it in constant space. I suggested to him that whenever I will encounter an element and if it is smaller than n, then I will make element negative at that index. Then I will traverse the whole array again and if I find any index whose value is non-negative, its means that element is not present and it is the first missing positive no. If no such no. is found then the answer will be n ( size of the array ) + 1. But this approach will not work for an array containing negative and repetitive no. So I improved my code to handle the negative and repetitive no.

He was very much satisfied with my approach. In the end, he asked me to ask a question to him. I asked him how can I improve more. He seemed to be very much impressed by me. He told me that I am very sharp in handling all the edges cases and I am very focussed.

Result: SELECTED

**Some important tips: **

1. Always believe in your self.

2. Communication skills matter a lot in the interview.

3. Luck is an important factor, you can not ignore it.

4. Always be positive in life. No matter how difficult the situation do not give up.

5. Practise and patient is the key.

#interview experiences #amazon #marketing #interview

1653475560

## A Pure PHP Implementation Of The MessagePack Serialization Format

msgpack.php

A pure PHP implementation of the MessagePack serialization format.

## Installation

The recommended way to install the library is through Composer:

``````composer require rybakit/msgpack
``````

## Usage

### Packing

To pack values you can either use an instance of a `Packer`:

``````\$packer = new Packer();
\$packed = \$packer->pack(\$value);
``````

or call a static method on the `MessagePack` class:

``````\$packed = MessagePack::pack(\$value);
``````

In the examples above, the method `pack` automatically packs a value depending on its type. However, not all PHP types can be uniquely translated to MessagePack types. For example, the MessagePack format defines `map` and `array` types, which are represented by a single `array` type in PHP. By default, the packer will pack a PHP array as a MessagePack array if it has sequential numeric keys, starting from `0` and as a MessagePack map otherwise:

``````\$mpArr1 = \$packer->pack([1, 2]);               // MP array [1, 2]
\$mpArr2 = \$packer->pack([0 => 1, 1 => 2]);     // MP array [1, 2]
\$mpMap1 = \$packer->pack([0 => 1, 2 => 3]);     // MP map {0: 1, 2: 3}
\$mpMap2 = \$packer->pack([1 => 2, 2 => 3]);     // MP map {1: 2, 2: 3}
\$mpMap3 = \$packer->pack(['a' => 1, 'b' => 2]); // MP map {a: 1, b: 2}
``````

However, sometimes you need to pack a sequential array as a MessagePack map. To do this, use the `packMap` method:

``````\$mpMap = \$packer->packMap([1, 2]); // {0: 1, 1: 2}
``````

Here is a list of type-specific packing methods:

``````\$packer->packNil();           // MP nil
\$packer->packBool(true);      // MP bool
\$packer->packInt(42);         // MP int
\$packer->packFloat(M_PI);     // MP float (32 or 64)
\$packer->packFloat32(M_PI);   // MP float 32
\$packer->packFloat64(M_PI);   // MP float 64
\$packer->packStr('foo');      // MP str
\$packer->packBin("\x80");     // MP bin
\$packer->packArray([1, 2]);   // MP array
\$packer->packMap(['a' => 1]); // MP map
\$packer->packExt(1, "\xaa");  // MP ext
``````

Check the "Custom types" section below on how to pack custom types.

#### Packing options

The `Packer` object supports a number of bitmask-based options for fine-tuning the packing process (defaults are in bold):

The type detection mode (`DETECT_STR_BIN`/`DETECT_ARR_MAP`) adds some overhead which can be noticed when you pack large (16- and 32-bit) arrays or strings. However, if you know the value type in advance (for example, you only work with UTF-8 strings or/and associative arrays), you can eliminate this overhead by forcing the packer to use the appropriate type, which will save it from running the auto-detection routine. Another option is to explicitly specify the value type. The library provides 2 auxiliary classes for this, `Map` and `Bin`. Check the "Custom types" section below for details.

Examples:

``````// detect str/bin type and pack PHP 64-bit floats (doubles) to MP 32-bit floats
\$packer = new Packer(PackOptions::DETECT_STR_BIN | PackOptions::FORCE_FLOAT32);

// these will throw MessagePack\Exception\InvalidOptionException
\$packer = new Packer(PackOptions::FORCE_STR | PackOptions::FORCE_BIN);
\$packer = new Packer(PackOptions::FORCE_FLOAT32 | PackOptions::FORCE_FLOAT64);
``````

### Unpacking

To unpack data you can either use an instance of a `BufferUnpacker`:

``````\$unpacker = new BufferUnpacker();

\$unpacker->reset(\$packed);
\$value = \$unpacker->unpack();
``````

or call a static method on the `MessagePack` class:

``````\$value = MessagePack::unpack(\$packed);
``````

If the packed data is received in chunks (e.g. when reading from a stream), use the `tryUnpack` method, which attempts to unpack data and returns an array of unpacked messages (if any) instead of throwing an `InsufficientDataException`:

``````while (\$chunk = ...) {
\$unpacker->append(\$chunk);
if (\$messages = \$unpacker->tryUnpack()) {
return \$messages;
}
}
``````

If you want to unpack from a specific position in a buffer, use `seek`:

``````\$unpacker->seek(42); // set position equal to 42 bytes
\$unpacker->seek(-8); // set position to 8 bytes before the end of the buffer
``````

To skip bytes from the current position, use `skip`:

``````\$unpacker->skip(10); // set position to 10 bytes ahead of the current position
``````

To get the number of remaining (unread) bytes in the buffer:

``````\$unreadBytesCount = \$unpacker->getRemainingCount();
``````

To check whether the buffer has unread data:

``````\$hasUnreadBytes = \$unpacker->hasRemaining();
``````

If needed, you can remove already read data from the buffer by calling:

``````\$releasedBytesCount = \$unpacker->release();
``````

With the `read` method you can read raw (packed) data:

``````\$packedData = \$unpacker->read(2); // read 2 bytes
``````

Besides the above methods `BufferUnpacker` provides type-specific unpacking methods, namely:

``````\$unpacker->unpackNil();   // PHP null
\$unpacker->unpackBool();  // PHP bool
\$unpacker->unpackInt();   // PHP int
\$unpacker->unpackFloat(); // PHP float
\$unpacker->unpackStr();   // PHP UTF-8 string
\$unpacker->unpackBin();   // PHP binary string
\$unpacker->unpackArray(); // PHP sequential array
\$unpacker->unpackMap();   // PHP associative array
\$unpacker->unpackExt();   // PHP MessagePack\Type\Ext object
``````

#### Unpacking options

The `BufferUnpacker` object supports a number of bitmask-based options for fine-tuning the unpacking process (defaults are in bold):

1. The binary MessagePack format has unsigned 64-bit as its largest integer data type, but PHP does not support such integers, which means that an overflow can occur during unpacking.

2. Make sure the GMP extension is enabled.

3. Make sure the Decimal extension is enabled.

Examples:

``````\$packedUint64 = "\xcf"."\xff\xff\xff\xff"."\xff\xff\xff\xff";

\$unpacker = new BufferUnpacker(\$packedUint64);
var_dump(\$unpacker->unpack()); // string(20) "18446744073709551615"

\$unpacker = new BufferUnpacker(\$packedUint64, UnpackOptions::BIGINT_AS_GMP);
var_dump(\$unpacker->unpack()); // object(GMP) {...}

\$unpacker = new BufferUnpacker(\$packedUint64, UnpackOptions::BIGINT_AS_DEC);
var_dump(\$unpacker->unpack()); // object(Decimal\Decimal) {...}
``````

### Custom types

In addition to the basic types, the library provides functionality to serialize and deserialize arbitrary types. This can be done in several ways, depending on your use case. Let's take a look at them.

#### Type objects

If you need to serialize an instance of one of your classes into one of the basic MessagePack types, the best way to do this is to implement the CanBePacked interface in the class. A good example of such a class is the `Map` type class that comes with the library. This type is useful when you want to explicitly specify that a given PHP array should be packed as a MessagePack map without triggering an automatic type detection routine:

``````\$packer = new Packer();

\$packedMap = \$packer->pack(new Map([1, 2, 3]));
\$packedArray = \$packer->pack([1, 2, 3]);
``````

More type examples can be found in the src/Type directory.

#### Type transformers

As with type objects, type transformers are only responsible for serializing values. They should be used when you need to serialize a value that does not implement the CanBePacked interface. Examples of such values could be instances of built-in or third-party classes that you don't own, or non-objects such as resources.

A transformer class must implement the CanPack interface. To use a transformer, it must first be registered in the packer. Here is an example of how to serialize PHP streams into the MessagePack `bin` format type using one of the supplied transformers, `StreamTransformer`:

``````\$packer = new Packer(null, [new StreamTransformer()]);

\$packedBin = \$packer->pack(fopen('/path/to/file', 'r+'));
``````

More type transformer examples can be found in the src/TypeTransformer directory.

#### Extensions

In contrast to the cases described above, extensions are intended to handle extension types and are responsible for both serialization and deserialization of values (types).

An extension class must implement the Extension interface. To use an extension, it must first be registered in the packer and the unpacker.

The MessagePack specification divides extension types into two groups: predefined and application-specific. Currently, there is only one predefined type in the specification, Timestamp.

Timestamp

The Timestamp extension type is a predefined type. Support for this type in the library is done through the `TimestampExtension` class. This class is responsible for handling `Timestamp` objects, which represent the number of seconds and optional adjustment in nanoseconds:

``````\$timestampExtension = new TimestampExtension();

\$packer = new Packer();
\$packer = \$packer->extendWith(\$timestampExtension);

\$unpacker = new BufferUnpacker();
\$unpacker = \$unpacker->extendWith(\$timestampExtension);

\$packedTimestamp = \$packer->pack(Timestamp::now());
\$timestamp = \$unpacker->reset(\$packedTimestamp)->unpack();

\$seconds = \$timestamp->getSeconds();
\$nanoseconds = \$timestamp->getNanoseconds();
``````

When using the `MessagePack` class, the Timestamp extension is already registered:

``````\$packedTimestamp = MessagePack::pack(Timestamp::now());
\$timestamp = MessagePack::unpack(\$packedTimestamp);
``````

Application-specific extensions

In addition, the format can be extended with your own types. For example, to make the built-in PHP `DateTime` objects first-class citizens in your code, you can create a corresponding extension, as shown in the example. Please note, that custom extensions have to be registered with a unique extension ID (an integer from `0` to `127`).

More extension examples can be found in the examples/MessagePack directory.

## Exceptions

If an error occurs during packing/unpacking, a `PackingFailedException` or an `UnpackingFailedException` will be thrown, respectively. In addition, an `InsufficientDataException` can be thrown during unpacking.

An `InvalidOptionException` will be thrown in case an invalid option (or a combination of mutually exclusive options) is used.

## Tests

Run tests as follows:

``````vendor/bin/phpunit
``````

Also, if you already have Docker installed, you can run the tests in a docker container. First, create a container:

``````./dockerfile.sh | docker build -t msgpack -
``````

The command above will create a container named `msgpack` with PHP 8.1 runtime. You may change the default runtime by defining the `PHP_IMAGE` environment variable:

``````PHP_IMAGE='php:8.0-cli' ./dockerfile.sh | docker build -t msgpack -
``````

See a list of various images here.

Then run the unit tests:

``````docker run --rm -v \$PWD:/msgpack -w /msgpack msgpack
``````

#### Fuzzing

To ensure that the unpacking works correctly with malformed/semi-malformed data, you can use a testing technique called Fuzzing. The library ships with a help file (target) for PHP-Fuzzer and can be used as follows:

``````php-fuzzer fuzz tests/fuzz_buffer_unpacker.php
``````

#### Performance

To check performance, run:

``````php -n -dzend_extension=opcache.so \
-dpcre.jit=1 -dopcache.enable=1 -dopcache.enable_cli=1 \
tests/bench.php
``````

Example output

``````Filter: MessagePack\Tests\Perf\Filter\ListFilter
Rounds: 3
Iterations: 100000

=============================================
Test/Target            Packer  BufferUnpacker
---------------------------------------------
nil .................. 0.0030 ........ 0.0139
false ................ 0.0037 ........ 0.0144
true ................. 0.0040 ........ 0.0137
7-bit uint #1 ........ 0.0052 ........ 0.0120
7-bit uint #2 ........ 0.0059 ........ 0.0114
7-bit uint #3 ........ 0.0061 ........ 0.0119
5-bit sint #1 ........ 0.0067 ........ 0.0126
5-bit sint #2 ........ 0.0064 ........ 0.0132
5-bit sint #3 ........ 0.0066 ........ 0.0135
8-bit uint #1 ........ 0.0078 ........ 0.0200
8-bit uint #2 ........ 0.0077 ........ 0.0212
8-bit uint #3 ........ 0.0086 ........ 0.0203
16-bit uint #1 ....... 0.0111 ........ 0.0271
16-bit uint #2 ....... 0.0115 ........ 0.0260
16-bit uint #3 ....... 0.0103 ........ 0.0273
32-bit uint #1 ....... 0.0116 ........ 0.0326
32-bit uint #2 ....... 0.0118 ........ 0.0332
32-bit uint #3 ....... 0.0127 ........ 0.0325
64-bit uint #1 ....... 0.0140 ........ 0.0277
64-bit uint #2 ....... 0.0134 ........ 0.0294
64-bit uint #3 ....... 0.0134 ........ 0.0281
8-bit int #1 ......... 0.0086 ........ 0.0241
8-bit int #2 ......... 0.0089 ........ 0.0225
8-bit int #3 ......... 0.0085 ........ 0.0229
16-bit int #1 ........ 0.0118 ........ 0.0280
16-bit int #2 ........ 0.0121 ........ 0.0270
16-bit int #3 ........ 0.0109 ........ 0.0274
32-bit int #1 ........ 0.0128 ........ 0.0346
32-bit int #2 ........ 0.0118 ........ 0.0339
32-bit int #3 ........ 0.0135 ........ 0.0368
64-bit int #1 ........ 0.0138 ........ 0.0276
64-bit int #2 ........ 0.0132 ........ 0.0286
64-bit int #3 ........ 0.0137 ........ 0.0274
64-bit int #4 ........ 0.0180 ........ 0.0285
64-bit float #1 ...... 0.0134 ........ 0.0284
64-bit float #2 ...... 0.0125 ........ 0.0275
64-bit float #3 ...... 0.0126 ........ 0.0283
fix string #1 ........ 0.0035 ........ 0.0133
fix string #2 ........ 0.0094 ........ 0.0216
fix string #3 ........ 0.0094 ........ 0.0222
fix string #4 ........ 0.0091 ........ 0.0241
8-bit string #1 ...... 0.0122 ........ 0.0301
8-bit string #2 ...... 0.0118 ........ 0.0304
8-bit string #3 ...... 0.0119 ........ 0.0315
16-bit string #1 ..... 0.0150 ........ 0.0388
16-bit string #2 ..... 0.1545 ........ 0.1665
32-bit string ........ 0.1570 ........ 0.1756
wide char string #1 .. 0.0091 ........ 0.0236
wide char string #2 .. 0.0122 ........ 0.0313
8-bit binary #1 ...... 0.0100 ........ 0.0302
8-bit binary #2 ...... 0.0123 ........ 0.0324
8-bit binary #3 ...... 0.0126 ........ 0.0327
16-bit binary ........ 0.0168 ........ 0.0372
32-bit binary ........ 0.1588 ........ 0.1754
fix array #1 ......... 0.0042 ........ 0.0131
fix array #2 ......... 0.0294 ........ 0.0367
fix array #3 ......... 0.0412 ........ 0.0472
16-bit array #1 ...... 0.1378 ........ 0.1596
16-bit array #2 ........... S ............. S
32-bit array .............. S ............. S
complex array ........ 0.1865 ........ 0.2283
fix map #1 ........... 0.0725 ........ 0.1048
fix map #2 ........... 0.0319 ........ 0.0405
fix map #3 ........... 0.0356 ........ 0.0665
fix map #4 ........... 0.0465 ........ 0.0497
16-bit map #1 ........ 0.2540 ........ 0.3028
16-bit map #2 ............. S ............. S
32-bit map ................ S ............. S
complex map .......... 0.2372 ........ 0.2710
fixext 1 ............. 0.0283 ........ 0.0358
fixext 2 ............. 0.0291 ........ 0.0371
fixext 4 ............. 0.0302 ........ 0.0355
fixext 8 ............. 0.0288 ........ 0.0384
fixext 16 ............ 0.0293 ........ 0.0359
8-bit ext ............ 0.0302 ........ 0.0439
16-bit ext ........... 0.0334 ........ 0.0499
32-bit ext ........... 0.1845 ........ 0.1888
32-bit timestamp #1 .. 0.0337 ........ 0.0547
32-bit timestamp #2 .. 0.0335 ........ 0.0560
64-bit timestamp #1 .. 0.0371 ........ 0.0575
64-bit timestamp #2 .. 0.0374 ........ 0.0542
64-bit timestamp #3 .. 0.0356 ........ 0.0533
96-bit timestamp #1 .. 0.0362 ........ 0.0699
96-bit timestamp #2 .. 0.0381 ........ 0.0701
96-bit timestamp #3 .. 0.0367 ........ 0.0687
=============================================
Total                  2.7618          4.0820
Skipped                     4               4
Failed                      0               0
Ignored                     0               0
``````

With JIT:

``````php -n -dzend_extension=opcache.so \
-dpcre.jit=1 -dopcache.jit_buffer_size=64M -dopcache.jit=tracing -dopcache.enable=1 -dopcache.enable_cli=1 \
tests/bench.php
``````

Example output

``````Filter: MessagePack\Tests\Perf\Filter\ListFilter
Rounds: 3
Iterations: 100000

=============================================
Test/Target            Packer  BufferUnpacker
---------------------------------------------
nil .................. 0.0005 ........ 0.0054
false ................ 0.0004 ........ 0.0059
true ................. 0.0004 ........ 0.0059
7-bit uint #1 ........ 0.0010 ........ 0.0047
7-bit uint #2 ........ 0.0010 ........ 0.0046
7-bit uint #3 ........ 0.0010 ........ 0.0046
5-bit sint #1 ........ 0.0025 ........ 0.0046
5-bit sint #2 ........ 0.0023 ........ 0.0046
5-bit sint #3 ........ 0.0024 ........ 0.0045
8-bit uint #1 ........ 0.0043 ........ 0.0081
8-bit uint #2 ........ 0.0043 ........ 0.0079
8-bit uint #3 ........ 0.0041 ........ 0.0080
16-bit uint #1 ....... 0.0064 ........ 0.0095
16-bit uint #2 ....... 0.0064 ........ 0.0091
16-bit uint #3 ....... 0.0064 ........ 0.0094
32-bit uint #1 ....... 0.0085 ........ 0.0114
32-bit uint #2 ....... 0.0077 ........ 0.0122
32-bit uint #3 ....... 0.0077 ........ 0.0120
64-bit uint #1 ....... 0.0085 ........ 0.0159
64-bit uint #2 ....... 0.0086 ........ 0.0157
64-bit uint #3 ....... 0.0086 ........ 0.0158
8-bit int #1 ......... 0.0042 ........ 0.0080
8-bit int #2 ......... 0.0042 ........ 0.0080
8-bit int #3 ......... 0.0042 ........ 0.0081
16-bit int #1 ........ 0.0065 ........ 0.0095
16-bit int #2 ........ 0.0065 ........ 0.0090
16-bit int #3 ........ 0.0056 ........ 0.0085
32-bit int #1 ........ 0.0067 ........ 0.0107
32-bit int #2 ........ 0.0066 ........ 0.0106
32-bit int #3 ........ 0.0063 ........ 0.0104
64-bit int #1 ........ 0.0072 ........ 0.0162
64-bit int #2 ........ 0.0073 ........ 0.0174
64-bit int #3 ........ 0.0072 ........ 0.0164
64-bit int #4 ........ 0.0077 ........ 0.0161
64-bit float #1 ...... 0.0053 ........ 0.0135
64-bit float #2 ...... 0.0053 ........ 0.0135
64-bit float #3 ...... 0.0052 ........ 0.0135
fix string #1 ....... -0.0002 ........ 0.0044
fix string #2 ........ 0.0035 ........ 0.0067
fix string #3 ........ 0.0035 ........ 0.0077
fix string #4 ........ 0.0033 ........ 0.0078
8-bit string #1 ...... 0.0059 ........ 0.0110
8-bit string #2 ...... 0.0063 ........ 0.0121
8-bit string #3 ...... 0.0064 ........ 0.0124
16-bit string #1 ..... 0.0099 ........ 0.0146
16-bit string #2 ..... 0.1522 ........ 0.1474
32-bit string ........ 0.1511 ........ 0.1483
wide char string #1 .. 0.0039 ........ 0.0084
wide char string #2 .. 0.0073 ........ 0.0123
8-bit binary #1 ...... 0.0040 ........ 0.0112
8-bit binary #2 ...... 0.0075 ........ 0.0123
8-bit binary #3 ...... 0.0077 ........ 0.0129
16-bit binary ........ 0.0096 ........ 0.0145
32-bit binary ........ 0.1535 ........ 0.1479
fix array #1 ......... 0.0008 ........ 0.0061
fix array #2 ......... 0.0121 ........ 0.0165
fix array #3 ......... 0.0193 ........ 0.0222
16-bit array #1 ...... 0.0607 ........ 0.0479
16-bit array #2 ........... S ............. S
32-bit array .............. S ............. S
complex array ........ 0.0749 ........ 0.0824
fix map #1 ........... 0.0329 ........ 0.0431
fix map #2 ........... 0.0161 ........ 0.0189
fix map #3 ........... 0.0205 ........ 0.0262
fix map #4 ........... 0.0252 ........ 0.0205
16-bit map #1 ........ 0.1016 ........ 0.0927
16-bit map #2 ............. S ............. S
32-bit map ................ S ............. S
complex map .......... 0.1096 ........ 0.1030
fixext 1 ............. 0.0157 ........ 0.0161
fixext 2 ............. 0.0175 ........ 0.0183
fixext 4 ............. 0.0156 ........ 0.0185
fixext 8 ............. 0.0163 ........ 0.0184
fixext 16 ............ 0.0164 ........ 0.0182
8-bit ext ............ 0.0158 ........ 0.0207
16-bit ext ........... 0.0203 ........ 0.0219
32-bit ext ........... 0.1614 ........ 0.1539
32-bit timestamp #1 .. 0.0195 ........ 0.0249
32-bit timestamp #2 .. 0.0188 ........ 0.0260
64-bit timestamp #1 .. 0.0207 ........ 0.0281
64-bit timestamp #2 .. 0.0212 ........ 0.0291
64-bit timestamp #3 .. 0.0207 ........ 0.0295
96-bit timestamp #1 .. 0.0222 ........ 0.0358
96-bit timestamp #2 .. 0.0228 ........ 0.0353
96-bit timestamp #3 .. 0.0210 ........ 0.0319
=============================================
Total                  1.6432          1.9674
Skipped                     4               4
Failed                      0               0
Ignored                     0               0
``````

You may change default benchmark settings by defining the following environment variables:

For example:

``````export MP_BENCH_TARGETS=pure_p
export MP_BENCH_ITERATIONS=1000000
export MP_BENCH_ROUNDS=5
# a comma separated list of test names
export MP_BENCH_TESTS='complex array, complex map'
# or a group name
# export MP_BENCH_TESTS='-@slow' // @pecl_comp
# or a regexp
# export MP_BENCH_TESTS='/complex (array|map)/'
``````

Another example, benchmarking both the library and the PECL extension:

``````MP_BENCH_TARGETS=pure_p,pure_u,pecl_p,pecl_u \
php -n -dextension=msgpack.so -dzend_extension=opcache.so \
-dpcre.jit=1 -dopcache.enable=1 -dopcache.enable_cli=1 \
tests/bench.php
``````

Example output

``````Filter: MessagePack\Tests\Perf\Filter\ListFilter
Rounds: 3
Iterations: 100000

===========================================================================
Test/Target            Packer  BufferUnpacker  msgpack_pack  msgpack_unpack
---------------------------------------------------------------------------
nil .................. 0.0031 ........ 0.0141 ...... 0.0055 ........ 0.0064
false ................ 0.0039 ........ 0.0154 ...... 0.0056 ........ 0.0053
true ................. 0.0038 ........ 0.0139 ...... 0.0056 ........ 0.0044
7-bit uint #1 ........ 0.0061 ........ 0.0110 ...... 0.0059 ........ 0.0046
7-bit uint #2 ........ 0.0065 ........ 0.0119 ...... 0.0042 ........ 0.0029
7-bit uint #3 ........ 0.0054 ........ 0.0117 ...... 0.0045 ........ 0.0025
5-bit sint #1 ........ 0.0047 ........ 0.0103 ...... 0.0038 ........ 0.0022
5-bit sint #2 ........ 0.0048 ........ 0.0117 ...... 0.0038 ........ 0.0022
5-bit sint #3 ........ 0.0046 ........ 0.0102 ...... 0.0038 ........ 0.0023
8-bit uint #1 ........ 0.0063 ........ 0.0174 ...... 0.0039 ........ 0.0031
8-bit uint #2 ........ 0.0063 ........ 0.0167 ...... 0.0040 ........ 0.0029
8-bit uint #3 ........ 0.0063 ........ 0.0168 ...... 0.0039 ........ 0.0030
16-bit uint #1 ....... 0.0092 ........ 0.0222 ...... 0.0049 ........ 0.0030
16-bit uint #2 ....... 0.0096 ........ 0.0227 ...... 0.0042 ........ 0.0046
16-bit uint #3 ....... 0.0123 ........ 0.0274 ...... 0.0059 ........ 0.0051
32-bit uint #1 ....... 0.0136 ........ 0.0331 ...... 0.0060 ........ 0.0048
32-bit uint #2 ....... 0.0130 ........ 0.0336 ...... 0.0070 ........ 0.0048
32-bit uint #3 ....... 0.0127 ........ 0.0329 ...... 0.0051 ........ 0.0048
64-bit uint #1 ....... 0.0126 ........ 0.0268 ...... 0.0055 ........ 0.0049
64-bit uint #2 ....... 0.0135 ........ 0.0281 ...... 0.0052 ........ 0.0046
64-bit uint #3 ....... 0.0131 ........ 0.0274 ...... 0.0069 ........ 0.0044
8-bit int #1 ......... 0.0077 ........ 0.0236 ...... 0.0058 ........ 0.0044
8-bit int #2 ......... 0.0087 ........ 0.0244 ...... 0.0058 ........ 0.0048
8-bit int #3 ......... 0.0084 ........ 0.0241 ...... 0.0055 ........ 0.0049
16-bit int #1 ........ 0.0112 ........ 0.0271 ...... 0.0048 ........ 0.0045
16-bit int #2 ........ 0.0124 ........ 0.0292 ...... 0.0057 ........ 0.0049
16-bit int #3 ........ 0.0118 ........ 0.0270 ...... 0.0058 ........ 0.0050
32-bit int #1 ........ 0.0137 ........ 0.0366 ...... 0.0058 ........ 0.0051
32-bit int #2 ........ 0.0133 ........ 0.0366 ...... 0.0056 ........ 0.0049
32-bit int #3 ........ 0.0129 ........ 0.0350 ...... 0.0052 ........ 0.0048
64-bit int #1 ........ 0.0145 ........ 0.0254 ...... 0.0034 ........ 0.0025
64-bit int #2 ........ 0.0097 ........ 0.0214 ...... 0.0034 ........ 0.0025
64-bit int #3 ........ 0.0096 ........ 0.0287 ...... 0.0059 ........ 0.0050
64-bit int #4 ........ 0.0143 ........ 0.0277 ...... 0.0059 ........ 0.0046
64-bit float #1 ...... 0.0134 ........ 0.0281 ...... 0.0057 ........ 0.0052
64-bit float #2 ...... 0.0141 ........ 0.0281 ...... 0.0057 ........ 0.0050
64-bit float #3 ...... 0.0144 ........ 0.0282 ...... 0.0057 ........ 0.0050
fix string #1 ........ 0.0036 ........ 0.0143 ...... 0.0066 ........ 0.0053
fix string #2 ........ 0.0107 ........ 0.0222 ...... 0.0065 ........ 0.0068
fix string #3 ........ 0.0116 ........ 0.0245 ...... 0.0063 ........ 0.0069
fix string #4 ........ 0.0105 ........ 0.0253 ...... 0.0083 ........ 0.0077
8-bit string #1 ...... 0.0126 ........ 0.0318 ...... 0.0075 ........ 0.0088
8-bit string #2 ...... 0.0121 ........ 0.0295 ...... 0.0076 ........ 0.0086
8-bit string #3 ...... 0.0125 ........ 0.0293 ...... 0.0130 ........ 0.0093
16-bit string #1 ..... 0.0159 ........ 0.0368 ...... 0.0117 ........ 0.0086
16-bit string #2 ..... 0.1547 ........ 0.1686 ...... 0.1516 ........ 0.1373
32-bit string ........ 0.1558 ........ 0.1729 ...... 0.1511 ........ 0.1396
wide char string #1 .. 0.0098 ........ 0.0237 ...... 0.0066 ........ 0.0065
wide char string #2 .. 0.0128 ........ 0.0291 ...... 0.0061 ........ 0.0082
8-bit binary #1 ........... I ............. I ........... F ............. I
8-bit binary #2 ........... I ............. I ........... F ............. I
8-bit binary #3 ........... I ............. I ........... F ............. I
16-bit binary ............. I ............. I ........... F ............. I
32-bit binary ............. I ............. I ........... F ............. I
fix array #1 ......... 0.0040 ........ 0.0129 ...... 0.0120 ........ 0.0058
fix array #2 ......... 0.0279 ........ 0.0390 ...... 0.0143 ........ 0.0165
fix array #3 ......... 0.0415 ........ 0.0463 ...... 0.0162 ........ 0.0187
16-bit array #1 ...... 0.1349 ........ 0.1628 ...... 0.0334 ........ 0.0341
16-bit array #2 ........... S ............. S ........... S ............. S
32-bit array .............. S ............. S ........... S ............. S
complex array ............. I ............. I ........... F ............. F
fix map #1 ................ I ............. I ........... F ............. I
fix map #2 ........... 0.0345 ........ 0.0391 ...... 0.0143 ........ 0.0168
fix map #3 ................ I ............. I ........... F ............. I
fix map #4 ........... 0.0459 ........ 0.0473 ...... 0.0151 ........ 0.0163
16-bit map #1 ........ 0.2518 ........ 0.2962 ...... 0.0400 ........ 0.0490
16-bit map #2 ............. S ............. S ........... S ............. S
32-bit map ................ S ............. S ........... S ............. S
complex map .......... 0.2380 ........ 0.2682 ...... 0.0545 ........ 0.0579
fixext 1 .................. I ............. I ........... F ............. F
fixext 2 .................. I ............. I ........... F ............. F
fixext 4 .................. I ............. I ........... F ............. F
fixext 8 .................. I ............. I ........... F ............. F
fixext 16 ................. I ............. I ........... F ............. F
8-bit ext ................. I ............. I ........... F ............. F
16-bit ext ................ I ............. I ........... F ............. F
32-bit ext ................ I ............. I ........... F ............. F
32-bit timestamp #1 ....... I ............. I ........... F ............. F
32-bit timestamp #2 ....... I ............. I ........... F ............. F
64-bit timestamp #1 ....... I ............. I ........... F ............. F
64-bit timestamp #2 ....... I ............. I ........... F ............. F
64-bit timestamp #3 ....... I ............. I ........... F ............. F
96-bit timestamp #1 ....... I ............. I ........... F ............. F
96-bit timestamp #2 ....... I ............. I ........... F ............. F
96-bit timestamp #3 ....... I ............. I ........... F ............. F
===========================================================================
Total                  1.5625          2.3866        0.7735          0.7243
Skipped                     4               4             4               4
Failed                      0               0            24              17
Ignored                    24              24             0               7
``````

With JIT:

``````MP_BENCH_TARGETS=pure_p,pure_u,pecl_p,pecl_u \
php -n -dextension=msgpack.so -dzend_extension=opcache.so \
-dpcre.jit=1 -dopcache.jit_buffer_size=64M -dopcache.jit=tracing -dopcache.enable=1 -dopcache.enable_cli=1 \
tests/bench.php
``````

Example output

``````Filter: MessagePack\Tests\Perf\Filter\ListFilter
Rounds: 3
Iterations: 100000

===========================================================================
Test/Target            Packer  BufferUnpacker  msgpack_pack  msgpack_unpack
---------------------------------------------------------------------------
nil .................. 0.0001 ........ 0.0052 ...... 0.0053 ........ 0.0042
false ................ 0.0007 ........ 0.0060 ...... 0.0057 ........ 0.0043
true ................. 0.0008 ........ 0.0060 ...... 0.0056 ........ 0.0041
7-bit uint #1 ........ 0.0031 ........ 0.0046 ...... 0.0062 ........ 0.0041
7-bit uint #2 ........ 0.0021 ........ 0.0043 ...... 0.0062 ........ 0.0041
7-bit uint #3 ........ 0.0022 ........ 0.0044 ...... 0.0061 ........ 0.0040
5-bit sint #1 ........ 0.0030 ........ 0.0048 ...... 0.0062 ........ 0.0040
5-bit sint #2 ........ 0.0032 ........ 0.0046 ...... 0.0062 ........ 0.0040
5-bit sint #3 ........ 0.0031 ........ 0.0046 ...... 0.0062 ........ 0.0040
8-bit uint #1 ........ 0.0054 ........ 0.0079 ...... 0.0062 ........ 0.0050
8-bit uint #2 ........ 0.0051 ........ 0.0079 ...... 0.0064 ........ 0.0044
8-bit uint #3 ........ 0.0051 ........ 0.0082 ...... 0.0062 ........ 0.0044
16-bit uint #1 ....... 0.0077 ........ 0.0094 ...... 0.0065 ........ 0.0045
16-bit uint #2 ....... 0.0077 ........ 0.0094 ...... 0.0063 ........ 0.0045
16-bit uint #3 ....... 0.0077 ........ 0.0095 ...... 0.0064 ........ 0.0047
32-bit uint #1 ....... 0.0088 ........ 0.0119 ...... 0.0063 ........ 0.0043
32-bit uint #2 ....... 0.0089 ........ 0.0117 ...... 0.0062 ........ 0.0039
32-bit uint #3 ....... 0.0089 ........ 0.0118 ...... 0.0063 ........ 0.0044
64-bit uint #1 ....... 0.0097 ........ 0.0155 ...... 0.0063 ........ 0.0045
64-bit uint #2 ....... 0.0095 ........ 0.0153 ...... 0.0061 ........ 0.0045
64-bit uint #3 ....... 0.0096 ........ 0.0156 ...... 0.0063 ........ 0.0047
8-bit int #1 ......... 0.0053 ........ 0.0083 ...... 0.0062 ........ 0.0044
8-bit int #2 ......... 0.0052 ........ 0.0080 ...... 0.0062 ........ 0.0044
8-bit int #3 ......... 0.0052 ........ 0.0080 ...... 0.0062 ........ 0.0043
16-bit int #1 ........ 0.0089 ........ 0.0097 ...... 0.0069 ........ 0.0046
16-bit int #2 ........ 0.0075 ........ 0.0093 ...... 0.0063 ........ 0.0043
16-bit int #3 ........ 0.0075 ........ 0.0094 ...... 0.0062 ........ 0.0046
32-bit int #1 ........ 0.0086 ........ 0.0122 ...... 0.0063 ........ 0.0044
32-bit int #2 ........ 0.0087 ........ 0.0120 ...... 0.0066 ........ 0.0046
32-bit int #3 ........ 0.0086 ........ 0.0121 ...... 0.0060 ........ 0.0044
64-bit int #1 ........ 0.0096 ........ 0.0149 ...... 0.0060 ........ 0.0045
64-bit int #2 ........ 0.0096 ........ 0.0157 ...... 0.0062 ........ 0.0044
64-bit int #3 ........ 0.0096 ........ 0.0160 ...... 0.0063 ........ 0.0046
64-bit int #4 ........ 0.0097 ........ 0.0157 ...... 0.0061 ........ 0.0044
64-bit float #1 ...... 0.0079 ........ 0.0153 ...... 0.0056 ........ 0.0044
64-bit float #2 ...... 0.0079 ........ 0.0152 ...... 0.0057 ........ 0.0045
64-bit float #3 ...... 0.0079 ........ 0.0155 ...... 0.0057 ........ 0.0044
fix string #1 ........ 0.0010 ........ 0.0045 ...... 0.0071 ........ 0.0044
fix string #2 ........ 0.0048 ........ 0.0075 ...... 0.0070 ........ 0.0060
fix string #3 ........ 0.0048 ........ 0.0086 ...... 0.0068 ........ 0.0060
fix string #4 ........ 0.0050 ........ 0.0088 ...... 0.0070 ........ 0.0059
8-bit string #1 ...... 0.0081 ........ 0.0129 ...... 0.0069 ........ 0.0062
8-bit string #2 ...... 0.0086 ........ 0.0128 ...... 0.0069 ........ 0.0065
8-bit string #3 ...... 0.0086 ........ 0.0126 ...... 0.0115 ........ 0.0065
16-bit string #1 ..... 0.0105 ........ 0.0137 ...... 0.0128 ........ 0.0068
16-bit string #2 ..... 0.1510 ........ 0.1486 ...... 0.1526 ........ 0.1391
32-bit string ........ 0.1517 ........ 0.1475 ...... 0.1504 ........ 0.1370
wide char string #1 .. 0.0044 ........ 0.0085 ...... 0.0067 ........ 0.0057
wide char string #2 .. 0.0081 ........ 0.0125 ...... 0.0069 ........ 0.0063
8-bit binary #1 ........... I ............. I ........... F ............. I
8-bit binary #2 ........... I ............. I ........... F ............. I
8-bit binary #3 ........... I ............. I ........... F ............. I
16-bit binary ............. I ............. I ........... F ............. I
32-bit binary ............. I ............. I ........... F ............. I
fix array #1 ......... 0.0014 ........ 0.0059 ...... 0.0132 ........ 0.0055
fix array #2 ......... 0.0146 ........ 0.0156 ...... 0.0155 ........ 0.0148
fix array #3 ......... 0.0211 ........ 0.0229 ...... 0.0179 ........ 0.0180
16-bit array #1 ...... 0.0673 ........ 0.0498 ...... 0.0343 ........ 0.0388
16-bit array #2 ........... S ............. S ........... S ............. S
32-bit array .............. S ............. S ........... S ............. S
complex array ............. I ............. I ........... F ............. F
fix map #1 ................ I ............. I ........... F ............. I
fix map #2 ........... 0.0148 ........ 0.0180 ...... 0.0156 ........ 0.0179
fix map #3 ................ I ............. I ........... F ............. I
fix map #4 ........... 0.0252 ........ 0.0201 ...... 0.0214 ........ 0.0167
16-bit map #1 ........ 0.1027 ........ 0.0836 ...... 0.0388 ........ 0.0510
16-bit map #2 ............. S ............. S ........... S ............. S
32-bit map ................ S ............. S ........... S ............. S
complex map .......... 0.1104 ........ 0.1010 ...... 0.0556 ........ 0.0602
fixext 1 .................. I ............. I ........... F ............. F
fixext 2 .................. I ............. I ........... F ............. F
fixext 4 .................. I ............. I ........... F ............. F
fixext 8 .................. I ............. I ........... F ............. F
fixext 16 ................. I ............. I ........... F ............. F
8-bit ext ................. I ............. I ........... F ............. F
16-bit ext ................ I ............. I ........... F ............. F
32-bit ext ................ I ............. I ........... F ............. F
32-bit timestamp #1 ....... I ............. I ........... F ............. F
32-bit timestamp #2 ....... I ............. I ........... F ............. F
64-bit timestamp #1 ....... I ............. I ........... F ............. F
64-bit timestamp #2 ....... I ............. I ........... F ............. F
64-bit timestamp #3 ....... I ............. I ........... F ............. F
96-bit timestamp #1 ....... I ............. I ........... F ............. F
96-bit timestamp #2 ....... I ............. I ........... F ............. F
96-bit timestamp #3 ....... I ............. I ........... F ............. F
===========================================================================
Total                  0.9642          1.0909        0.8224          0.7213
Skipped                     4               4             4               4
Failed                      0               0            24              17
Ignored                    24              24             0               7
``````

Note that the msgpack extension (v2.1.2) doesn't support ext, bin and UTF-8 str types.

The library is released under the MIT License. See the bundled LICENSE file for details.

Author: rybakit
Source Code: https://github.com/rybakit/msgpack.php

1648641360

## Treebender

A symbolic natural language parsing library for Rust, inspired by HDPSG.

## What is this?

This is a library for parsing natural or constructed languages into syntax trees and feature structures. There's no machine learning or probabilistic models, everything is hand-crafted and deterministic.

You can find out more about the motivations of this project in this blog post.

### But what are you using it for?

I'm using this to parse a constructed language for my upcoming xenolinguistics game, Themengi.

## Motivation

Using a simple 80-line grammar, introduced in the tutorial below, we can parse a simple subset of English, checking reflexive pronoun binding, case, and number agreement.

``````\$ cargo run --bin cli examples/reflexives.fgr
> she likes himself
Parsed 0 trees

> her likes herself
Parsed 0 trees

> she like herself
Parsed 0 trees

> she likes herself
Parsed 1 tree
(0..3: S
(0..1: N (0..1: she))
(1..2: TV (1..2: likes))
(2..3: N (2..3: herself)))
[
child-2: [
case: acc
pron: ref
needs_pron: #0 she
num: sg
child-0: [ word: herself ]
]
child-1: [
tense: nonpast
child-0: [ word: likes ]
num: #1 sg
]
child-0: [
child-0: [ word: she ]
case: nom
pron: #0
num: #1
]
]
``````

Low resource language? Low problem! No need to train on gigabytes of text, just write a grammar using your brain. Let's hypothesize that in American Sign Language, topicalized nouns (expressed with raised eyebrows) must appear first in the sentence. We can write a small grammar (18 lines), and plug in some sentences:

``````\$ cargo run --bin cli examples/asl-wordorder.fgr -n
> boy sit
Parsed 1 tree
(0..2: S
(0..1: NP ((0..1: N (0..1: boy))))
(1..2: IV (1..2: sit)))

> boy throw ball
Parsed 1 tree
(0..3: S
(0..1: NP ((0..1: N (0..1: boy))))
(1..2: TV (1..2: throw))
(2..3: NP ((2..3: N (2..3: ball)))))

> ball nm-raised-eyebrows boy throw
Parsed 1 tree
(0..4: S
(0..2: NP
(0..1: N (0..1: ball))
(1..2: Topic (1..2: nm-raised-eyebrows)))
(2..3: NP ((2..3: N (2..3: boy))))
(3..4: TV (3..4: throw)))

> boy throw ball nm-raised-eyebrows
Parsed 0 trees
``````

## Tutorial

As an example, let's say we want to build a parser for English reflexive pronouns (himself, herself, themselves, themself, itself). We'll also support number ("He likes X" v.s. "They like X") and simple embedded clauses ("He said that they like X").

Grammar files are written in a custom language, similar to BNF, called Feature GRammar (.fgr). There's a VSCode syntax highlighting extension for these files available as `fgr-syntax`.

We'll start by defining our lexicon. The lexicon is the set of terminal symbols (symbols in the actual input) that the grammar will match. Terminal symbols must start with a lowercase letter, and non-terminal symbols must start with an uppercase letter.

``````// pronouns
N -> he
N -> him
N -> himself
N -> she
N -> her
N -> herself
N -> they
N -> them
N -> themselves
N -> themself

// names, lowercase as they are terminals
N -> mary
N -> sue
N -> takeshi
N -> robert

// complementizer
Comp -> that

// verbs -- intransitive, transitive, and clausal
IV -> falls
IV -> fall
IV -> fell

TV -> likes
TV -> like
TV -> liked

CV -> says
CV -> say
CV -> said
``````

Next, we can add our sentence rules (they must be added at the top, as the first rule in the file is assumed to be the top-level rule):

``````// sentence rules
S -> N IV
S -> N TV N
S -> N CV Comp S

// ... previous lexicon ...
``````

Assuming this file is saved as `examples/no-features.fgr` (which it is :wink:), we can test this file with the built-in CLI:

``````\$ cargo run --bin cli examples/no-features.fgr
> he falls
Parsed 1 tree
(0..2: S
(0..1: N (0..1: he))
(1..2: IV (1..2: falls)))
[
child-1: [ child-0: [ word: falls ] ]
child-0: [ child-0: [ word: he ] ]
]

> he falls her
Parsed 0 trees

> he likes her
Parsed 1 tree
(0..3: S
(0..1: N (0..1: he))
(1..2: TV (1..2: likes))
(2..3: N (2..3: her)))
[
child-2: [ child-0: [ word: her ] ]
child-1: [ child-0: [ word: likes ] ]
child-0: [ child-0: [ word: he ] ]
]

> he likes
Parsed 0 trees

> he said that he likes her
Parsed 1 tree
(0..6: S
(0..1: N (0..1: he))
(1..2: CV (1..2: said))
(2..3: Comp (2..3: that))
(3..6: S
(3..4: N (3..4: he))
(4..5: TV (4..5: likes))
(5..6: N (5..6: her))))
[
child-0: [ child-0: [ word: he ] ]
child-2: [ child-0: [ word: that ] ]
child-1: [ child-0: [ word: said ] ]
child-3: [
child-2: [ child-0: [ word: her ] ]
child-1: [ child-0: [ word: likes ] ]
child-0: [ child-0: [ word: he ] ]
]
]

> he said that he
Parsed 0 trees
``````

This grammar already parses some correct sentences, and blocks some trivially incorrect ones. However, it doesn't care about number, case, or reflexives right now:

``````> she likes himself  // unbound reflexive pronoun
Parsed 1 tree
(0..3: S
(0..1: N (0..1: she))
(1..2: TV (1..2: likes))
(2..3: N (2..3: himself)))
[
child-0: [ child-0: [ word: she ] ]
child-2: [ child-0: [ word: himself ] ]
child-1: [ child-0: [ word: likes ] ]
]

> him like her  // incorrect case on the subject pronoun, should be nominative
// (he) instead of accusative (him)
Parsed 1 tree
(0..3: S
(0..1: N (0..1: him))
(1..2: TV (1..2: like))
(2..3: N (2..3: her)))
[
child-0: [ child-0: [ word: him ] ]
child-1: [ child-0: [ word: like ] ]
child-2: [ child-0: [ word: her ] ]
]

> he like her  // incorrect verb number agreement
Parsed 1 tree
(0..3: S
(0..1: N (0..1: he))
(1..2: TV (1..2: like))
(2..3: N (2..3: her)))
[
child-2: [ child-0: [ word: her ] ]
child-1: [ child-0: [ word: like ] ]
child-0: [ child-0: [ word: he ] ]
]
``````

To fix this, we need to add features to our lexicon, and restrict the sentence rules based on features.

Features are added with square brackets, and are key: value pairs separated by commas. `**top**` is a special feature value, which basically means "unspecified" -- we'll come back to it later. Features that are unspecified are also assumed to have a `**top**` value, but sometimes explicitly stating top is more clear.

``````/// Pronouns
// * num: sg or pl, whether this noun wants a singular verb (likes) or
//   a plural verb (like). note this is grammatical number, so for example
//   singular they takes plural agreement ("they like X", not *"they likes X")
// * case: nom or acc, whether this noun is nominative or accusative case.
//   nominative case goes in the subject, and accusative in the object.
//   e.g., "he fell" and "she likes him", not *"him fell" and *"her likes he"
// * pron: he, she, they, or ref -- what type of pronoun this is
// * needs_pron: whether this is a reflexive that needs to bind to another
//   pronoun.
N[ num: sg, case: nom, pron: he ]                    -> he
N[ num: sg, case: acc, pron: he ]                    -> him
N[ num: sg, case: acc, pron: ref, needs_pron: he ]   -> himself
N[ num: sg, case: nom, pron: she ]                   -> she
N[ num: sg, case: acc, pron: she ]                   -> her
N[ num: sg, case: acc, pron: ref, needs_pron: she]   -> herself
N[ num: pl, case: nom, pron: they ]                  -> they
N[ num: pl, case: acc, pron: they ]                  -> them
N[ num: pl, case: acc, pron: ref, needs_pron: they ] -> themselves
N[ num: sg, case: acc, pron: ref, needs_pron: they ] -> themself

// Names
// * num: sg, as people are singular ("mary likes her" / *"mary like her")
// * case: **top**, as names can be both subjects and objects
//   ("mary likes her" / "she likes mary")
// * pron: whichever pronoun the person uses for reflexive agreement
//   mary    pron: she  => mary likes herself
//   sue     pron: they => sue likes themself
//   takeshi pron: he   => takeshi likes himself
N[ num: sg, case: **top**, pron: she ]  -> mary
N[ num: sg, case: **top**, pron: they ] -> sue
N[ num: sg, case: **top**, pron: he ]   -> takeshi
N[ num: sg, case: **top**, pron: he ]   -> robert

// Complementizer doesn't need features
Comp -> that

// Verbs -- intransitive, transitive, and clausal
// * num: sg, pl, or **top** -- to match the noun numbers.
//   **top** will match either sg or pl, as past-tense verbs in English
//   don't agree in number: "he fell" and "they fell" are both fine
// * tense: past or nonpast -- this won't be used for agreement, but will be
//   copied into the final feature structure, and the client code could do
//   something with it
IV[ num:      sg, tense: nonpast ] -> falls
IV[ num:      pl, tense: nonpast ] -> fall
IV[ num: **top**, tense: past ]    -> fell

TV[ num:      sg, tense: nonpast ] -> likes
TV[ num:      pl, tense: nonpast ] -> like
TV[ num: **top**, tense: past ]    -> liked

CV[ num:      sg, tense: nonpast ] -> says
CV[ num:      pl, tense: nonpast ] -> say
CV[ num: **top**, tense: past ]    -> said
``````

Now that our lexicon is updated with features, we can update our sentence rules to constrain parsing based on those features. This uses two new features, tags and unification. Tags allow features to be associated between nodes in a rule, and unification controls how those features are compatible. The rules for unification are:

1. A string feature can unify with a string feature with the same value
2. A top feature can unify with anything, and the nodes are merged
3. A complex feature ([ ... ] structure) is recursively unified with another complex feature.

If unification fails anywhere, the parse is aborted and the tree is discarded. This allows the programmer to discard trees if features don't match.

``````// Sentence rules
// Intransitive verb:
// * Subject must be nominative case
// * Subject and verb must agree in number (copied through #1)
S -> N[ case: nom, num: #1 ] IV[ num: #1 ]
// Transitive verb:
// * Subject must be nominative case
// * Subject and verb must agree in number (copied through #2)
// * If there's a reflexive in the object position, make sure its `needs_pron`
//   feature matches the subject's `pron` feature. If the object isn't a
//   reflexive, then its `needs_pron` feature will implicitly be `**top**`, so
//   will unify with anything.
S -> N[ case: nom, pron: #1, num: #2 ] TV[ num: #2 ] N[ case: acc, needs_pron: #1 ]
// Clausal verb:
// * Subject must be nominative case
// * Subject and verb must agree in number (copied through #1)
// * Reflexives can't cross clause boundaries (*"He said that she likes himself"),
//   so we can ignore reflexives and delegate to inner clause rule
S -> N[ case: nom, num: #1 ] CV[ num: #1 ] Comp S
``````

Now that we have this augmented grammar (available as `examples/reflexives.fgr`), we can try it out and see that it rejects illicit sentences that were previously accepted, while still accepting valid ones:

``````> he fell
Parsed 1 tree
(0..2: S
(0..1: N (0..1: he))
(1..2: IV (1..2: fell)))
[
child-1: [
child-0: [ word: fell ]
num: #0 sg
tense: past
]
child-0: [
pron: he
case: nom
num: #0
child-0: [ word: he ]
]
]

> he like him
Parsed 0 trees

> he likes himself
Parsed 1 tree
(0..3: S
(0..1: N (0..1: he))
(1..2: TV (1..2: likes))
(2..3: N (2..3: himself)))
[
child-1: [
num: #0 sg
child-0: [ word: likes ]
tense: nonpast
]
child-2: [
needs_pron: #1 he
num: sg
child-0: [ word: himself ]
pron: ref
case: acc
]
child-0: [
child-0: [ word: he ]
pron: #1
num: #0
case: nom
]
]

> he likes herself
Parsed 0 trees

> mary likes herself
Parsed 1 tree
(0..3: S
(0..1: N (0..1: mary))
(1..2: TV (1..2: likes))
(2..3: N (2..3: herself)))
[
child-0: [
pron: #0 she
num: #1 sg
case: nom
child-0: [ word: mary ]
]
child-1: [
tense: nonpast
child-0: [ word: likes ]
num: #1
]
child-2: [
child-0: [ word: herself ]
num: sg
pron: ref
case: acc
needs_pron: #0
]
]

> mary likes themself
Parsed 0 trees

> sue likes themself
Parsed 1 tree
(0..3: S
(0..1: N (0..1: sue))
(1..2: TV (1..2: likes))
(2..3: N (2..3: themself)))
[
child-0: [
pron: #0 they
child-0: [ word: sue ]
case: nom
num: #1 sg
]
child-1: [
tense: nonpast
num: #1
child-0: [ word: likes ]
]
child-2: [
needs_pron: #0
case: acc
pron: ref
child-0: [ word: themself ]
num: sg
]
]

> sue likes himself
Parsed 0 trees
``````

If this is interesting to you and you want to learn more, you can check out my blog series, the excellent textbook Syntactic Theory: A Formal Introduction (2nd ed.), and the DELPH-IN project, whose work on the LKB inspired this simplified version.

## Using from code

I need to write this section in more detail, but if you're comfortable with Rust, I suggest looking through the codebase. It's not perfect, it started as one of my first Rust projects (after migrating through F# -> TypeScript -> C in search of the right performance/ergonomics tradeoff), and it could use more tests, but overall it's not too bad.

Basically, the processing pipeline is:

1. Make a `Grammar` struct
• `Grammar` is defined in `rules.rs`.
• The easiest way to make a `Grammar` is `Grammar::parse_from_file`, which is mostly a hand-written recusive descent parser in `parse_grammar.rs`. Yes, I recognize the irony here.
1. It takes input (in `Grammar::parse`, which does everything for you, or `Grammar::parse_chart`, which just does the chart)
2. The input is first chart-parsed in `earley.rs`
3. Then, a forest is built from the chart, in `forest.rs`, using an algorithm I found in a very useful blog series I forget the URL for, because the algorithms in the academic literature for this are... weird.
4. Finally, the feature unification is used to prune the forest down to only valid trees. It would be more efficient to do this during parsing, but meh.

The most interesting thing you can do via code and not via the CLI is probably getting at the raw feature DAG, as that would let you do things like pronoun coreference. The DAG code is in `featurestructure.rs`, and should be fairly approachable -- there's a lot of Rust ceremony around `Rc<RefCell<...>>` because using an arena allocation crate seemed too harlike overkill, but that is somewhat mitigated by the `NodeRef` type alias. Hit me up at https://vgel.me/contact if you need help with anything here!

Author: vgel
Source Code: https://github.com/vgel/treebender

1630743562

## A Wrapper for Sembast and SQFlite to Enable Easy

FHIR_DB

This is really just a wrapper around Sembast_SQFLite - so all of the heavy lifting was done by Alex Tekartik. I highly recommend that if you have any questions about working with this package that you take a look at Sembast. He's also just a super nice guy, and even answered a question for me when I was deciding which sembast version to use. As usual, ResoCoder also has a good tutorial.

I have an interest in low-resource settings and thus a specific reason to be able to store data offline. To encourage this use, there are a number of other packages I have created based around the data format FHIR. FHIR® is the registered trademark of HL7 and is used with the permission of HL7. Use of the FHIR trademark does not constitute endorsement of this product by HL7.

## Using the Db

So, while not absolutely necessary, I highly recommend that you use some sort of interface class. This adds the benefit of more easily handling errors, plus if you change to a different database in the future, you don't have to change the rest of your app, just the interface.

I've used something like this in my projects:

``````class IFhirDb {
IFhirDb();
final ResourceDao resourceDao = ResourceDao();

Future<Either<DbFailure, Resource>> save(Resource resource) async {
Resource resultResource;
try {
resultResource = await resourceDao.save(resource);
} catch (error) {
return left(DbFailure.unableToSave(error: error.toString()));
}
return right(resultResource);
}

Future<Either<DbFailure, List<Resource>>> returnListOfSingleResourceType(
String resourceType) async {
List<Resource> resultList;
try {
resultList =
await resourceDao.getAllSortedById(resourceType: resourceType);
} catch (error) {
return left(DbFailure.unableToObtainList(error: error.toString()));
}
return right(resultList);
}

Future<Either<DbFailure, List<Resource>>> searchFunction(
String resourceType, String searchString, String reference) async {
List<Resource> resultList;
try {
resultList =
await resourceDao.searchFor(resourceType, searchString, reference);
} catch (error) {
return left(DbFailure.unableToObtainList(error: error.toString()));
}
return right(resultList);
}
}
``````

I like this because in case there's an i/o error or something, it won't crash your app. Then, you can call this interface in your app like the following:

``````final patient = Patient(
resourceType: 'Patient',
name: [HumanName(text: 'New Patient Name')],
birthDate: Date(DateTime.now()),
);

final saveResult = await IFhirDb().save(patient);
``````

This will save your newly created patient to the locally embedded database.

IMPORTANT: this database will expect that all previously created resources have an id. When you save a resource, it will check to see if that resource type has already been stored. (Each resource type is saved in it's own store in the database). It will then check if there is an ID. If there's no ID, it will create a new one for that resource (along with metadata on version number and creation time). It will save it, and return the resource. If it already has an ID, it will copy the the old version of the resource into a _history store. It will then update the metadata of the new resource and save that version into the appropriate store for that resource. If, for instance, we have a previously created patient:

``````{
"resourceType": "Patient",
"id": "fhirfli-294057507-6811107",
"meta": {
"versionId": "1",
"lastUpdated": "2020-10-16T19:41:28.054369Z"
},
"name": [
{
"given": ["New"],
"family": "Patient"
}
],
"birthDate": "2020-10-16"
}
``````

And we update the last name to 'Provider'. The above version of the patient will be kept in _history, while in the 'Patient' store in the db, we will have the updated version:

``````{
"resourceType": "Patient",
"id": "fhirfli-294057507-6811107",
"meta": {
"versionId": "2",
"lastUpdated": "2020-10-16T19:45:07.316698Z"
},
"name": [
{
"given": ["New"],
"family": "Provider"
}
],
"birthDate": "2020-10-16"
}
``````

This way we can keep track of all previous version of all resources (which is obviously important in medicine).

For most of the interactions (saving, deleting, etc), they work the way you'd expect. The only difference is search. Because Sembast is NoSQL, we can search on any of the fields in a resource. If in our interface class, we have the following function:

``````  Future<Either<DbFailure, List<Resource>>> searchFunction(
String resourceType, String searchString, String reference) async {
List<Resource> resultList;
try {
resultList =
await resourceDao.searchFor(resourceType, searchString, reference);
} catch (error) {
return left(DbFailure.unableToObtainList(error: error.toString()));
}
return right(resultList);
}
``````

You can search for all immunizations of a certain patient:

``````searchFunction(
'Immunization', 'patient.reference', 'Patient/\$patientId');
``````

This function will search through all entries in the 'Immunization' store. It will look at all 'patient.reference' fields, and return any that match 'Patient/\$patientId'.

The last thing I'll mention is that this is a password protected db, using AES-256 encryption (although it can also use Salsa20). Anytime you use the db, you have the option of using a password for encryption/decryption. Remember, if you setup the database using encryption, you will only be able to access it using that same password. When you're ready to change the password, you will need to call the update password function. If we again assume we created a change password method in our interface, it might look something like this:

``````class IFhirDb {
IFhirDb();
final ResourceDao resourceDao = ResourceDao();
...
try {
} catch (error) {
}
return right(Unit);
}
``````

You don't have to use a password, and in that case, it will save the db file as plain text. If you want to add a password later, it will encrypt it at that time.

### General Store

After using this for a while in an app, I've realized that it needs to be able to store data apart from just FHIR resources, at least on occasion. For this, I've added a second class for all versions of the database called GeneralDao. This is similar to the ResourceDao, but fewer options. So, in order to save something, it would look like this:

``````await GeneralDao().save('password', {'new':'map'});
``````

The difference between these two options is that the first one will generate a key for the map being stored, while the second will store the map using the key provided. Both will return the key after successfully storing the map.

Other functions available include:

``````// deletes everything in the general store

// delete specific entry

// returns map with that key
``````

FHIR® is a registered trademark of Health Level Seven International (HL7) and its use does not constitute an endorsement of products by HL7®

## Use this package as a library

### Depend on it

Run this command:

With Flutter:

`` \$ flutter pub add fhir_db``

This will add a line like this to your package's pubspec.yaml (and run an implicit flutter pub get):

``````dependencies:
fhir_db: ^0.4.3``````

### Import it

Now in your Dart code, you can use:

``````import 'package:fhir_db/dstu2.dart';
import 'package:fhir_db/dstu2/fhir_db.dart';
import 'package:fhir_db/dstu2/general_dao.dart';
import 'package:fhir_db/dstu2/resource_dao.dart';
import 'package:fhir_db/encrypt/aes.dart';
import 'package:fhir_db/encrypt/salsa.dart';
import 'package:fhir_db/r4.dart';
import 'package:fhir_db/r4/fhir_db.dart';
import 'package:fhir_db/r4/general_dao.dart';
import 'package:fhir_db/r4/resource_dao.dart';
import 'package:fhir_db/r5.dart';
import 'package:fhir_db/r5/fhir_db.dart';
import 'package:fhir_db/r5/general_dao.dart';
import 'package:fhir_db/r5/resource_dao.dart';
import 'package:fhir_db/stu3.dart';
import 'package:fhir_db/stu3/fhir_db.dart';
import 'package:fhir_db/stu3/general_dao.dart';
import 'package:fhir_db/stu3/resource_dao.dart'; ``````

example/lib/main.dart

``````import 'package:fhir/r4.dart';
import 'package:fhir_db/r4.dart';
import 'package:flutter/material.dart';
import 'package:test/test.dart';

Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();

final resourceDao = ResourceDao();

// await resourceDao.updatePw('newPw', null);
await resourceDao.deleteAllResources(null);

test('Playing with Passwords', () async {
final patient = Patient(id: Id('1'));

final saved = await resourceDao.save(null, patient);

await resourceDao.updatePw(null, 'newPw');
final search1 = await resourceDao.find('newPw',
resourceType: R4ResourceType.Patient, id: Id('1'));
expect(saved, search1[0]);

resourceType: R4ResourceType.Patient, id: Id('1'));
expect(saved, search2[0]);

final search3 = await resourceDao.find(null,
resourceType: R4ResourceType.Patient, id: Id('1'));
expect(saved, search3[0]);

await resourceDao.deleteAllResources(null);
});
});

final id = Id('12345');
group('Saving Things:', () {
test('Save Patient', () async {
final humanName = HumanName(family: 'Atreides', given: ['Duke']);
final patient = Patient(id: id, name: [humanName]);
final saved = await resourceDao.save(null, patient);

expect(saved.id, id);

expect((saved as Patient).name?[0], humanName);
});

test('Save Organization', () async {
final organization = Organization(id: id, name: 'FhirFli');
final saved = await resourceDao.save(null, organization);

expect(saved.id, id);

expect((saved as Organization).name, 'FhirFli');
});

test('Save Observation1', () async {
final observation1 = Observation(
id: Id('obs1'),
code: CodeableConcept(text: 'Observation #1'),
effectiveDateTime: FhirDateTime(DateTime(1981, 09, 18)),
);
final saved = await resourceDao.save(null, observation1);

expect(saved.id, Id('obs1'));

expect((saved as Observation).code.text, 'Observation #1');
});

test('Save Observation1 Again', () async {
final observation1 = Observation(
id: Id('obs1'),
code: CodeableConcept(text: 'Observation #1 - Updated'));
final saved = await resourceDao.save(null, observation1);

expect(saved.id, Id('obs1'));

expect((saved as Observation).code.text, 'Observation #1 - Updated');

expect(saved.meta?.versionId, Id('2'));
});

test('Save Observation2', () async {
final observation2 = Observation(
id: Id('obs2'),
code: CodeableConcept(text: 'Observation #2'),
effectiveDateTime: FhirDateTime(DateTime(1981, 09, 18)),
);
final saved = await resourceDao.save(null, observation2);

expect(saved.id, Id('obs2'));

expect((saved as Observation).code.text, 'Observation #2');
});

test('Save Observation3', () async {
final observation3 = Observation(
id: Id('obs3'),
code: CodeableConcept(text: 'Observation #3'),
effectiveDateTime: FhirDateTime(DateTime(1981, 09, 18)),
);
final saved = await resourceDao.save(null, observation3);

expect(saved.id, Id('obs3'));

expect((saved as Observation).code.text, 'Observation #3');
});
});

group('Finding Things:', () {
test('Find 1st Patient', () async {
final search = await resourceDao.find(null,
resourceType: R4ResourceType.Patient, id: id);
final humanName = HumanName(family: 'Atreides', given: ['Duke']);

expect(search.length, 1);

expect((search[0] as Patient).name?[0], humanName);
});

test('Find 3rd Observation', () async {
final search = await resourceDao.find(null,
resourceType: R4ResourceType.Observation, id: Id('obs3'));

expect(search.length, 1);

expect(search[0].id, Id('obs3'));

expect((search[0] as Observation).code.text, 'Observation #3');
});

test('Find All Observations', () async {
final search = await resourceDao.getResourceType(
null,
resourceTypes: [R4ResourceType.Observation],
);

expect(search.length, 3);

final idList = [];
for (final obs in search) {
}

expect(idList.contains('obs1'), true);

expect(idList.contains('obs2'), true);

expect(idList.contains('obs3'), true);
});

test('Find All (non-historical) Resources', () async {
final search = await resourceDao.getAll(null);

expect(search.length, 5);
final patList = search.toList();
final orgList = search.toList();
final obsList = search.toList();
patList.retainWhere(
(resource) => resource.resourceType == R4ResourceType.Patient);
orgList.retainWhere(
(resource) => resource.resourceType == R4ResourceType.Organization);
obsList.retainWhere(
(resource) => resource.resourceType == R4ResourceType.Observation);

expect(patList.length, 1);

expect(orgList.length, 1);

expect(obsList.length, 3);
});
});

group('Deleting Things:', () {
test('Delete 2nd Observation', () async {
await resourceDao.delete(
null, null, R4ResourceType.Observation, Id('obs2'), null, null);

final search = await resourceDao.getResourceType(
null,
resourceTypes: [R4ResourceType.Observation],
);

expect(search.length, 2);

final idList = [];
for (final obs in search) {
}

expect(idList.contains('obs1'), true);

expect(idList.contains('obs2'), false);

expect(idList.contains('obs3'), true);
});

test('Delete All Observations', () async {
await resourceDao.deleteSingleType(null,
resourceType: R4ResourceType.Observation);

final search = await resourceDao.getAll(null);

expect(search.length, 2);

final patList = search.toList();
final orgList = search.toList();
patList.retainWhere(
(resource) => resource.resourceType == R4ResourceType.Patient);
orgList.retainWhere(
(resource) => resource.resourceType == R4ResourceType.Organization);

expect(patList.length, 1);

expect(patList.length, 1);
});

test('Delete All Resources', () async {
await resourceDao.deleteAllResources(null);

final search = await resourceDao.getAll(null);

expect(search.length, 0);
});
});

group('Password - Saving Things:', () {
test('Save Patient', () async {
await resourceDao.updatePw(null, 'newPw');
final humanName = HumanName(family: 'Atreides', given: ['Duke']);
final patient = Patient(id: id, name: [humanName]);
final saved = await resourceDao.save('newPw', patient);

expect(saved.id, id);

expect((saved as Patient).name?[0], humanName);
});

test('Save Organization', () async {
final organization = Organization(id: id, name: 'FhirFli');
final saved = await resourceDao.save('newPw', organization);

expect(saved.id, id);

expect((saved as Organization).name, 'FhirFli');
});

test('Save Observation1', () async {
final observation1 = Observation(
id: Id('obs1'),
code: CodeableConcept(text: 'Observation #1'),
effectiveDateTime: FhirDateTime(DateTime(1981, 09, 18)),
);
final saved = await resourceDao.save('newPw', observation1);

expect(saved.id, Id('obs1'));

expect((saved as Observation).code.text, 'Observation #1');
});

test('Save Observation1 Again', () async {
final observation1 = Observation(
id: Id('obs1'),
code: CodeableConcept(text: 'Observation #1 - Updated'));
final saved = await resourceDao.save('newPw', observation1);

expect(saved.id, Id('obs1'));

expect((saved as Observation).code.text, 'Observation #1 - Updated');

expect(saved.meta?.versionId, Id('2'));
});

test('Save Observation2', () async {
final observation2 = Observation(
id: Id('obs2'),
code: CodeableConcept(text: 'Observation #2'),
effectiveDateTime: FhirDateTime(DateTime(1981, 09, 18)),
);
final saved = await resourceDao.save('newPw', observation2);

expect(saved.id, Id('obs2'));

expect((saved as Observation).code.text, 'Observation #2');
});

test('Save Observation3', () async {
final observation3 = Observation(
id: Id('obs3'),
code: CodeableConcept(text: 'Observation #3'),
effectiveDateTime: FhirDateTime(DateTime(1981, 09, 18)),
);
final saved = await resourceDao.save('newPw', observation3);

expect(saved.id, Id('obs3'));

expect((saved as Observation).code.text, 'Observation #3');
});
});

group('Password - Finding Things:', () {
test('Find 1st Patient', () async {
final search = await resourceDao.find('newPw',
resourceType: R4ResourceType.Patient, id: id);
final humanName = HumanName(family: 'Atreides', given: ['Duke']);

expect(search.length, 1);

expect((search[0] as Patient).name?[0], humanName);
});

test('Find 3rd Observation', () async {
final search = await resourceDao.find('newPw',
resourceType: R4ResourceType.Observation, id: Id('obs3'));

expect(search.length, 1);

expect(search[0].id, Id('obs3'));

expect((search[0] as Observation).code.text, 'Observation #3');
});

test('Find All Observations', () async {
final search = await resourceDao.getResourceType(
'newPw',
resourceTypes: [R4ResourceType.Observation],
);

expect(search.length, 3);

final idList = [];
for (final obs in search) {
}

expect(idList.contains('obs1'), true);

expect(idList.contains('obs2'), true);

expect(idList.contains('obs3'), true);
});

test('Find All (non-historical) Resources', () async {
final search = await resourceDao.getAll('newPw');

expect(search.length, 5);
final patList = search.toList();
final orgList = search.toList();
final obsList = search.toList();
patList.retainWhere(
(resource) => resource.resourceType == R4ResourceType.Patient);
orgList.retainWhere(
(resource) => resource.resourceType == R4ResourceType.Organization);
obsList.retainWhere(
(resource) => resource.resourceType == R4ResourceType.Observation);

expect(patList.length, 1);

expect(orgList.length, 1);

expect(obsList.length, 3);
});
});

group('Password - Deleting Things:', () {
test('Delete 2nd Observation', () async {
await resourceDao.delete(
'newPw', null, R4ResourceType.Observation, Id('obs2'), null, null);

final search = await resourceDao.getResourceType(
'newPw',
resourceTypes: [R4ResourceType.Observation],
);

expect(search.length, 2);

final idList = [];
for (final obs in search) {
}

expect(idList.contains('obs1'), true);

expect(idList.contains('obs2'), false);

expect(idList.contains('obs3'), true);
});

test('Delete All Observations', () async {
await resourceDao.deleteSingleType('newPw',
resourceType: R4ResourceType.Observation);

final search = await resourceDao.getAll('newPw');

expect(search.length, 2);

final patList = search.toList();
final orgList = search.toList();
patList.retainWhere(
(resource) => resource.resourceType == R4ResourceType.Patient);
orgList.retainWhere(
(resource) => resource.resourceType == R4ResourceType.Organization);

expect(patList.length, 1);

expect(patList.length, 1);
});

test('Delete All Resources', () async {
await resourceDao.deleteAllResources('newPw');

final search = await resourceDao.getAll('newPw');

expect(search.length, 0);

await resourceDao.updatePw('newPw', null);
});
});
} ``````

Author: MayJuun

1642390128

## 파이썬 코딩 무료 강의 (활용편6) - 이미지 처리, 얼굴 인식을 통한 캐릭터 씌우기를 해보아요

파이썬 무료 강의 (활용편6 - 이미지 처리)입니다.
OpenCV 를 이용한 다양한 이미지 처리 기법과 재미있는 프로젝트를 진행합니다.
누구나 볼 수 있도록 쉽고 재미있게 제작하였습니다. ^^

[소개]
(0:00:00) 0.Intro
(0:00:31) 1.소개
(0:02:18) 2.활용편 6 이미지 처리 소개

[OpenCV 전반전]
(0:04:36) 3.환경설정
(0:08:41) 4.이미지 출력
(0:21:51) 5.동영상 출력 #1 파일
(0:29:58) 6.동영상 출력 #2 카메라
(0:34:23) 7.도형 그리기 #1 빈 스케치북
(0:39:49) 8.도형 그리기 #2 영역 색칠
(0:42:26) 9.도형 그리기 #3 직선
(0:51:23) 10.도형 그리기 #4 원
(0:55:09) 11.도형 그리기 #5 사각형
(0:58:32) 12.도형 그리기 #6 다각형
(1:09:23) 13.텍스트 #1 기본
(1:17:45) 14.텍스트 #2 한글 우회
(1:24:14) 15.파일 저장 #1 이미지
(1:29:27) 16.파일 저장 #2 동영상
(1:39:29) 17.크기 조정
(1:50:16) 18.이미지 자르기
(1:57:03) 19.이미지 대칭
(2:01:46) 20.이미지 회전
(2:06:07) 21.이미지 변형 - 흑백
(2:11:25) 22.이미지 변형 - 흐림
(2:18:03) 23.이미지 변형 - 원근 #1
(2:27:45) 24.이미지 변형 - 원근 #2

[반자동 문서 스캐너 프로젝트]
(2:32:50) 25.미니 프로젝트 1 - #1 마우스 이벤트 등록
(2:42:06) 26.미니 프로젝트 1 - #2 기본 코드 완성
(2:49:54) 27.미니 프로젝트 1 - #3 지점 선 긋기
(2:55:24) 28.미니 프로젝트 1 - #4 실시간 선 긋기

[OpenCV 후반전]
(3:01:52) 29.이미지 변형 - 이진화 #1 Trackbar
(3:14:37) 30.이미지 변형 - 이진화 #2 임계값
(3:20:26) 31.이미지 변형 - 이진화 #3 Adaptive Threshold
(3:28:34) 32.이미지 변형 - 이진화 #4 오츠 알고리즘
(3:32:22) 33.이미지 변환 - 팽창
(3:41:10) 34.이미지 변환 - 침식
(3:45:56) 35.이미지 변환 - 열림 & 닫힘
(3:54:10) 36.이미지 검출 - 경계선
(4:05:08) 37.이미지 검출 - 윤곽선 #1 기본
(4:15:26) 38.이미지 검출 - 윤곽선 #2 찾기 모드
(4:20:46) 39.이미지 검출 - 윤곽선 #3 면적

[카드 검출 & 분류기 프로젝트]
(4:27:42) 40.미니프로젝트 2

[퀴즈]
(4:31:57) 41.퀴즈

[얼굴인식 프로젝트]
(4:41:25) 42.환경설정 및 기본 코드 정리
(4:54:48) 43.눈과 코 인식하여 도형 그리기
(5:10:42) 44.그림판 이미지 씌우기
(5:20:52) 45.캐릭터 이미지 씌우기
(5:33:10) 46.보충설명
(5:40:53) 47.마치며 (학습 참고 자료)
(5:42:18) 48.Outro

[학습자료]
수업에 필요한 이미지, 동영상 자료 링크입니다.

고양이 이미지 : https://pixabay.com/images/id-2083492/
크기 : 640 x 390
파일명 : img.jpg

고양이 동영상 : https://www.pexels.com/video/7515833/
크기 : SD (360 x 640)
파일명 : video.mp4

신문 이미지 : https://pixabay.com/images/id-350376/
크기 : 1280 x 853
파일명 : newspaper.jpg

카드 이미지 1 : https://pixabay.com/images/id-682332/
크기 : 1280 x 1019
파일명 : poker.jpg

책 이미지 : https://www.pexels.com/photo/1029807/
크기 : Small (640 x 853)
파일명 : book.jpg

눈사람 이미지 : https://pixabay.com/images/id-1300089/
크기 : 1280 x 904
파일명 : snowman.png

카드 이미지 2 : https://pixabay.com/images/id-161404/
크기 : 640 x 408
파일명 : card.png

퀴즈용 동영상 : https://www.pexels.com/video/3121459/
크기 : HD (1280 x 720)
파일명 : city.mp4

프로젝트용 동영상 : https://www.pexels.com/video/3256542/
크기 : Full HD (1920 x 1080)
파일명 : face_video.mp4

파일명 : right_eye.png (100 x 100), left_eye.png (100 x 100), nose.png (300 x 100)

무료 이미지 편집 도구 : https://pixlr.com/kr/

#python #opencv

1597132860

## Amazon Interview Experience for SDE-1 | Amazon-WOW 2020

Amazon has a special program called AmazonWOW for women. It is to promote women in technology. It is a very good opportunity for women as they have to only compete with other females, not with males. The online application came in April. The program consists of a two-month internship for prefinal year student and fulltime plus Internship for final year student.

It consisted of a total 4 rounds, first was an online coding contest and then 3 telephonic interviews.

**Online test : **

The first round was an online coding round. It consisted of 2 coding questions and 28 MCQ. We had 1.2 hrs. The coding questions were quite simple but MCQs were very difficult. I would like to say that luck matters a lot in cracking online coding round.

1. First question: Find the longest common subsequence between two string. It is standard Dynamic programming question but the constraints were not very high so I solved it using recursion.

**2. Second question: **I did not find the exact question on any platform but it was very simple. You are given a string consisting of lowercase English alphabets, return the internet resource address of the string.

Internet resource address of a string is defined as

://.ru[/]

can be either http or ftp.

is a string consisting of lower case English alphabtes.

is a non mepty string of lower case English alphabtes.

Ex : httpsunrux -> http://sun.ru/x

For MCQs, you must have a strong grip on OOP and c++ language.:

**Round 1: **

For this round, I was given an amazon chime link and live code editor link in which I had to code. The interviewer started by asking me my introduction and then he gave his introduction. In my introduction, I told him about my passion for competitive coding, writing and reading.

Then Immediately we moved to coding questions. He told me that I have only 45 minutes to answer so I have to come up with the best approach possible.

1. First Question: Find x ^ y mod z. I gave him the O(log(y)) approach. I covered all the edge cases when x will be zero or negative when y will be zero or negative. When y will be negative, he told me to return an error to the user. I coded properly using indentation and suitable variable and function names. I used int to store the variable but when the value is very high I should use long long int. I missed this case. He then moved to the second question.

2. Second Question:  Given a set of dependencies I have to find one of the suitable ordering of the dependencies. I told him I will use topological sort for this. He told me to explain my approach and then I coded it. But while coding I missed an edge case when there will cycle in the dependency. He told me to correct my code. I corrected my code by checking if there is a cycle present in the dependency.

3. Third Question:  For this question, I gave him two-approaches, first one was linearly counting the no of x and second was using a modified binary search. He did not ask me to code this question.

The best part was that I had already solved all these questions before so I did not get nervous there. In the end, I asked him where I can improve, He told me to check code before finally submitting to the interviewer.

After 12 days the result of this round was declared.

**Round 2: **

For this round also, I was provided with the Amazon chime link and live code link. The interviewer asked me two questions.

1.** First Question:**  Add all greater values to every node in a given BST. I gave him O(n ) time complexity solution. Initially, I had written the wrong code but my approach was right. He dry ran my code, pointed out the mistake that I made in code and told me to correct the code. I corrected the code and he was satisfied by my approach. I told him about the time complexity ie O(n). I told him if we consider internal stack then space complexity will o(n) because in the worst case the height of BST can be O(n) if it is skewed BST.

**2. Second Question: ** But in this question, He gave me three conditions.

1. You can traverse the data structure in only one direction.

2. You cannot use extra space ie in-place algorithm.

3. You can use any data structure of your choice.

My first approach was to use an array data structure. I told him that in first traversal I will find the count of negative numbers and then I will start filling my result array. But he said I cannot use extra space.

My second approach was to use a binary search tree and the result will be inorder traversal of the tree. But he told me that I have to return the data structure which I am using.

Then He asked me what are the data structure that I know. I told him I know heap, queue, stack, singly-Linked list and doubly linked list. Then suddenly doubly-linkedList came to my mind and I told him I will use doubly LinkedList. He told me that in doubly-linked you can traverse in both directions. Then I told him that will use a singly linked list. He told me to write code and dry ran my code. He was satisfied with my code.

My second interviewer was a very helpful and knowledgeable person. In the end, he said “it was nice to interview you. ”

After 11 days the second-round result was declared.

**Round 3: **

For this round also, I was provided with the amazon chime link and live code link. The interviewer was a very nice and chill person. He tried to make me comfortable. He introduced himself and then I gave my brief introduction. In this round, I was asked two questions. One was a coding question and the other was OS( operating System ) question.

1. First question:  If we have a well-optimised code, On what factors the maximum no of threads in a process depends?

We had around half an hour discussion on this topic. I told him how threads are used in the client-server application, use of threads in a text editor which simultaneously performs writing, auto-correction and suggestions. He asked me if a site has 1 million clients, then 1 million threads will be created, I told him about the use of multiple servers. I told him the no. thread depends upon the resources of the machine. I told him it will depend upon the memory of the computer. Then He wanted to know, which memory affect it, primary memory or secondary memory. I told primary memory will affect the no of threads as all the processes/ threads reside in the primary memory. I was thinking of other factors also but then he moved to coding question.

After this, we moved to coding question.

**2. Second Question: **  Find the first missing positive number in an array.

My first approach was to use hashing, the time complexity of this approach was O(n ) and the space complexity was O(n). He told me to do it in constant space. I suggested to him that whenever I will encounter an element and if it is smaller than n, then I will make element negative at that index. Then I will traverse the whole array again and if I find any index whose value is non-negative, its means that element is not present and it is the first missing positive no. If no such no. is found then the answer will be n ( size of the array ) + 1. But this approach will not work for an array containing negative and repetitive no. So I improved my code to handle the negative and repetitive no.

He was very much satisfied with my approach. In the end, he asked me to ask a question to him. I asked him how can I improve more. He seemed to be very much impressed by me. He told me that I am very sharp in handling all the edges cases and I am very focussed.

Result: SELECTED

**Some important tips: **

1. Always believe in your self.

2. Communication skills matter a lot in the interview.

3. Luck is an important factor, you can not ignore it.

4. Always be positive in life. No matter how difficult the situation do not give up.

5. Practise and patient is the key.

#interview experiences #amazon #marketing #interview