Understand the Hazards of Using Imperative Code

JavaScript has been getting a lot of new, sugary features ever since we got over Harmony. While more features can allow us to write readable, high-quality code, it’s also easy to go overboard with what’s new and shiny and run into some of the potential pitfalls.

Let’s go over some of the gotchas I see come up quite frequently as sources of confusion, both new and old.

Arrow Functions and Object Literals

Arrow functions provide a terser and shorter syntax, one of the features available being that you can write your function as a lambda expression with an implicit return value. This comes in handy for functional-style code, like when you have to use mapping arrays using a function. That would be quite a few empty lines with regular functions.

For example:

const numbers = [1, 2, 3, 4];
numbers.map(function(n) {
  return n * n;
});

This becomes a sleek, easy-to-read one-liner with the lambda style arrow functions:

const numbers = [1, 2, 3, 4];
numbers.map(n => n * n);

This use case of an arrow function will work as one would expect: It multiplies the values by itself and returns to a new array containing [1, 4, 9, 16].

However, if you try mapping into objects, the syntax isn’t what one might intuitively expect it to be. For example, let’s say we’re trying to map our numbers into an array of objects containing the value like this:

const numbers = [1, 2, 3, 4];
numbers.map(n => { value: n });

The result here will actually be an array containing undefined values. While it might look like we are returning an object here, the interpreter sees something completely different. The curly braces are being interpreted as the block scope of the arrow function, and the value statement actually ends up being a label. If we were to extrapolate the above arrow function into what the interpreter actually ends up executing, it would look something like this:

const numbers = [1, 2, 3, 4];
numbers.map(function(n) {
  value:
  n
  return;
});

The workaround is quite subtle. We just need to wrap the object in parentheses, which turns it into an expression instead of a block statement, like this:

const numbers = [1, 2, 3, 4];
numbers.map(n => ({ value: n }));

This will evaluate to an array containing an array of objects with the values that one would expect.

Arrow Functions and Bindings

Another caveat with arrow functions is that they don’t have their own this binding, meaning their this value will be the same as the this value of the enclosing lexical scope.

So despite the syntax being arguably sleeker, arrow functions are not a replacement for good old functions. You can quickly run into situations where your this binding is not what you thought it was.

For example:

let calculator = {
  value: 0,
  add: (values) => {
    this.value = values.reduce((a, v) => a + v, this.value);
  },
};
calculator.add([1, 2, 3]);
console.log(calculator.value);

While one might expect the this binding here to be the calculator object there, it will actually result in this being either undefined or the global object depending on whether the code is running in strict mode or not. This is because the closest lexical scope here is the global scope. In strict mode, that is undefined; otherwise, it’s the window object in browsers (or the process object in a Node.js compatible environment).

Regular functions do have a this binding. When called on an object, this will point at the object, so using a regular function is still the way to go for member functions.

let calculator = {
  value: 0,
  add(values) {
    this.value = values.reduce((a, v) => a + v, this.value);
  },
};
calculator.add([10, 10]);
console.log(calculator.value);

Also, since an arrow function has no this binding, [Function.prototype.call](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call), [Function.prototype.bind](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind), and [Function.prototype.apply](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply) won’t work with them either. The this binding is set in stone when the arrow function was declared, and can’t change.

So in the following example, we’ll run into the same issue as we had earlier: The this binding is the global object when the adder’s add function is called, despite our attempt to override it with Function.prototype.call:

const adder = {
  add: (values) => {
    this.value = values.reduce((a, v) => a + v, this.value);
  },
};
let calculator = {
  value: 0
};
adder.add.call(calculator, [1, 2, 3]);

Arrow functions are neat, but they can’t replace regular member functions where a this binding is needed.

Automatic Semicolon Insertion

While it’s not a new feature, automatic semicolon insertion (ASI) is one of the weirder features in JavaScript, so it’s worth a mention. In theory, you can omit semicolons most of the time (which many projects do). If the project has a precedent, you should follow that, but you do, however, need to be aware that ASI is a feature, or you’ll end up having code that can be deceiving.

Take the following example:

return
{
  value: 42
}

One might think it would return the object literal, but it will actually return undefined because semicolon insertion takes place, making it an empty return statement followed by a block statement and a label statement.

In other words, the final code that is actually being interpreted looks more like the following:

return;
{
  value: 42
};

As a rule of thumb, never start a line with an opening brace, bracket, or template string literal, even when using semicolons because ASI always takes place.

Shallow Sets

Sets are shallow, meaning duplicate arrays and objects with the same values, which will lead to multiple entries in the set.

For example:

let set = new Set();
set.add([1, 2, 3]);
set.add([1, 2, 3]);
console.log(set.length);

The size of that set will be two, which makes sense if you think of it in terms of references as they are different objects.

Strings are immutable, however. Take the example of multiple strings in a set like this:

let set = new Set();
set.add([1, 2, 3].join(','));
set.add([1, 2, 3].join(','));
console.log(set.size);

This will end up with the set having a size of one because strings are immutable and interned in JavaScript, which can be used as a workaround if you find yourself needing to store a set of objects. One could serialize and de-serialize them instead.

Classes and the Temporal Dead Zone

In JavaScript, regular functions get hoisted to the top of the lexical scope, meaning the example below will work as one might expect:

let segment = new Segment();
function Segment() {
  this.x = 0;
  this.y = 0;
}

But the same is not true for classes. Classes are actually not hoisted and need to be fully defined in the lexical scope before you attempt to use them.

For example:

let segment = new Segment();
class Segment {
  constructor() {
    this.x = 0;
    this.y = 0;
  }
}

This will result in a ReferenceError when trying to construct a new instance of the class because they aren’t hoisted like functions are.

Finally

Finally is a bit of a special case. Take a look at the following snippet:

try {
  return true;
} finally {
  return false;
}

What value would you think it returns? The answer is both intuitive and at the same time can become unintuitive. One could think the first return statement makes the function actually return and pop the call stack. But this is the exception to that rule because Finally statements are always run so the return statement inside the Finally block returns instead.

In Conclusion

JavaScript is easy to learn but hard to master. In other words, it’s error-prone unless a developer is careful about what and why they’re doing something.

This is especially true with ECMAScript 6 and its sugary features. Arrow functions, in particular, come up all of the time. If I was to make a guess, I’d say it’s because developers see them as being prettier than regular functions. But they’re not regular functions and they can’t replace them.

Skimming the specification from time to time doesn’t hurt. It’s not the most exciting document in the world, but as far as specifications go, it’s not that bad.

Tools like the AST Explorer also help in shedding some light on what is going on in some of these corner cases. Humans and computers tend to parse things differently.

With that said, I’ll leave you with this final example as an exercise.

#javascript #code #programming

What is GEEK

Buddha Community

How to Use Hotwire Rails

Introduction

We are back with another exciting and much-talked-about Rails tutorial on how to use Hotwire with the Rails application. This Hotwire Rails tutorial is an alternate method for building modern web applications that consume a pinch of JavaScript.

Rails 7 Hotwire is the default front-end framework shipped with Rails 7 after it was launched. It is used to represent HTML over the wire in the Rails application. Previously, we used to add a hotwire-rails gem in our gem file and then run rails hotwire: install. However, with the introduction of Rails 7, the gem got deprecated. Now, we use turbo-rails and stimulus rails directly, which work as Hotwire’s SPA-like page accelerator and Hotwire’s modest JavaScript framework.

What is Hotwire?

Hotwire is a package of different frameworks that help to build applications. It simplifies the developer’s work for writing web pages without the need to write JavaScript, and instead sending HTML code over the wire.

Introduction to The Hotwire Framework:

1. Turbo:

It uses simplified techniques to build web applications while decreasing the usage of JavaScript in the application. Turbo offers numerous handling methods for the HTML data sent over the wire and displaying the application’s data without actually loading the entire page. It helps to maintain the simplicity of web applications without destroying the single-page application experience by using the below techniques:

Turbo Frames: Turbo Frames help to load the different sections of our markup without any dependency as it divides the page into different contexts separately called frames and updates these frames individually.
Turbo Drive: Every link doesn’t have to make the entire page reload when clicked. Only the HTML contained within the tag will be displayed.
Turbo Streams: To add real-time features to the application, this technique is used. It helps to bring real-time data to the application using CRUD actions.

2. Stimulus

It represents the JavaScript framework, which is required when JS is a requirement in the application. The interaction with the HTML is possible with the help of a stimulus, as the controllers that help those interactions are written by a stimulus.

3. Strada

Not much information is available about Strada as it has not been officially released yet. However, it works with native applications, and by using HTML bridge attributes, interaction is made possible between web applications and native apps.

Simple diagrammatic representation of Hotwire Stack:

Prerequisites For Hotwire Rails Tutorial

As we are implementing the Ruby on Rails Hotwire tutorial, make sure about the following installations before you can get started.

• Ruby on Rails
• Hotwire gem
• PostgreSQL/SQLite (choose any one database)
• Turbo Rails
• Stimulus.js

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Create a new Rails Project

Find the following commands to create a rails application.

mkdir ~/projects/railshotwire
cd ~/projects/railshotwire
echo "source 'https://rubygems.org'" > Gemfile
echo "gem 'rails', '~> 7.0.0'" >> Gemfile
bundle install  
bundle exec rails new . --force -d=postgresql

Now create some files for the project, up till now no usage of Rails Hotwire can be seen.
Fire the following command in your terminal.

• For creating a default controller for the application

echo "class HomeController < ApplicationController" > app/controllers/home_controller.rb
echo "end" >> app/controllers/home_controller.rb

• For creating another controller for the application

echo "class OtherController < ApplicationController" > app/controllers/other_controller.rb
echo "end" >> app/controllers/home_controller.rb

• For creating routes for the application

echo "Rails.application.routes.draw do" > config/routes.rb
echo '  get "home/index"' >> config/routes.rb
echo '  get "other/index"' >> config/routes.rb
echo '  root to: "home#index"' >> config/routes.rb
echo 'end' >> config/routes.rb

• For creating a default view for the application

mkdir app/views/home
echo '<h1>This is Rails Hotwire homepage</h1>' > app/views/home/index.html.erb
echo '<div><%= link_to "Enter to other page", other_index_path %></div>' >> app/views/home/index.html.erb

• For creating another view for the application

mkdir app/views/other
echo '<h1>This is Another page</h1>' > app/views/other/index.html.erb
echo '<div><%= link_to "Enter to home page", root_path %></div>' >> app/views/other/index.html.erb

• For creating a database and schema.rb file for the application

bin/rails db:create
bin/rails db:migrate

• For checking the application run bin/rails s and open your browser, your running application will have the below view.

Additionally, you can clone the code and browse through the project. Here’s the source code of the repository: Rails 7 Hotwire application

Now, let’s see how Hotwire Rails can work its magic with various Turbo techniques.

Hotwire Rails: Turbo Drive

Go to your localhost:3000 on your web browser and right-click on the Inspect and open a Network tab of the DevTools of the browser.

Now click on go to another page link that appears on the home page to redirect from the home page to another page. In our Network tab, we can see that this action of navigation is achieved via XHR. It appears only the part inside HTML is reloaded, here neither the CSS is reloaded nor the JS is reloaded when the navigation action is performed.

By performing this action we can see that Turbo Drive helps to represent the HTML response without loading the full page and only follows redirect and reindeer HTML responses which helps to make the application faster to access.

Hotwire Rails: Turbo Frame

This technique helps to divide the current page into different sections called frames that can be updated separately independently when new data is added from the server.
Below we discuss the different use cases of Turbo frame like inline edition, sorting, searching, and filtering of data.

Let’s perform some practical actions to see the example of these use cases.

Make changes in the app/controllers/home_controller.rb file

#CODE

class HomeController < ApplicationController
   def turbo_frame_form
   end
   
   def turbo_frame submit
      extracted_anynumber = params[:any][:anynumber]
      render :turbo_frame_form, status: :ok, locals: {anynumber: extracted_anynumber,      comment: 'turbo_frame_submit ok' }
   end
end

Add app/views/home/turbo_frame_form.html.erb file to the application and add this content inside the file.

#CODE

<section>

    <%= turbo_frame_tag 'anyframe' do %>
            
      <div>
          <h2>Frame view</h2>
          <%= form_with scope: :any, url: turbo_frame_submit_path, local: true do |form| %>
              <%= form.label :anynumber, 'Type an integer (odd or even)', 'class' => 'my-0  d-inline'  %>
              <%= form.text_field :anynumber, type: 'number', 'required' => 'true', 'value' => "#{local_assigns[:anynumber] || 0}",  'aria-describedby' => 'anynumber' %>
              <%= form.submit 'Submit this number', 'id' => 'submit-number' %>
          <% end %>
      </div>
      <div>
        <h2>Data of the view</h2>
        <pre style="font-size: .7rem;"><%= JSON.pretty_generate(local_assigns) %></pre> 
      </div>
      
    <% end %>

</section>

Make some adjustments in routes.rb

#CODE

Rails.application.routes.draw do
  get 'home/index'
  get 'other/index'

  get '/home/turbo_frame_form' => 'home#turbo_frame_form', as: 'turbo_frame_form'
  post '/home/turbo_frame_submit' => 'home#turbo_frame_submit', as: 'turbo_frame_submit'


  root to: "home#index"
end

• Next step is to change homepage view in app/views/home/index.html.erb

#CODE

<h1>This is Rails Hotwire home page</h1>
<div><%= link_to "Enter to other page", other_index_path %></div>

<%= turbo_frame_tag 'anyframe' do %>        
  <div>
      <h2>Home view</h2>
      <%= form_with scope: :any, url: turbo_frame_submit_path, local: true do |form| %>
          <%= form.label :anynumber, 'Type an integer (odd or even)', 'class' => 'my-0  d-inline'  %>
          <%= form.text_field :anynumber, type: 'number', 'required' => 'true', 'value' => "#{local_assigns[:anynumber] || 0}",  'aria-describedby' => 'anynumber' %>
          <%= form.submit 'Submit this number', 'id' => 'submit-number' %>
      <% end %>
  <div>
<% end %>

After making all the changes, restart the rails server and refresh the browser, the default view will appear on the browser.

Now in the field enter any digit, after entering the digit click on submit button, and as the submit button is clicked we can see the Turbo Frame in action in the below screen, we can observe that the frame part changed, the first title and first link didn’t move.

Hotwire Rails: Turbo Streams

Turbo Streams deliver page updates over WebSocket, SSE or in response to form submissions by only using HTML and a series of CRUD-like operations, you are free to say that either

• Update the piece of HTML while responding to all the other actions like the post, put, patch, and delete except the GET action.
• Transmit a change to all users, without reloading the browser page.

This transmit can be represented by a simple example.

• Make changes in app/controllers/other_controller.rb file of rails application

#CODE

class OtherController < ApplicationController

  def post_something
    respond_to do |format|
      format.turbo_stream {  }
    end
  end

   end

Add the below line in routes.rb file of the application

#CODE

post '/other/post_something' => 'other#post_something', as: 'post_something'

Superb! Rails will now attempt to locate the app/views/other/post_something.turbo_stream.erb template at any moment the ‘/other/post_something’ endpoint is reached.

For this, we need to add app/views/other/post_something.turbo_stream.erb template in the rails application.

#CODE

<turbo-stream action="append" target="messages">
  <template>
    <div id="message_1">This changes the existing message!</div>
  </template>
</turbo-stream>

This states that the response will try to append the template of the turbo frame with ID “messages”.

Now change the index.html.erb file in app/views/other paths with the below content.

#CODE

<h1>This is Another page</h1>
<div><%= link_to "Enter to home page", root_path %></div>

<div style="margin-top: 3rem;">
  <%= form_with scope: :any, url: post_something_path do |form| %>
      <%= form.submit 'Post any message %>
  <% end %>
  <turbo-frame id="messages">
    <div>An empty message</div>
  </turbo-frame>
</div>

• After making all the changes, restart the rails server and refresh the browser, and go to the other page.

• Once the above screen appears, click on the Post any message button

This action shows that after submitting the response, the Turbo Streams help the developer to append the message, without reloading the page.

Another use case we can test is that rather than appending the message, the developer replaces the message. For that, we need to change the content of app/views/other/post_something.turbo_stream.erb template file and change the value of the action attribute from append to replace and check the changes in the browser.

#CODE

<turbo-stream action="replace" target="messages">
  <template>
    <div id="message_1">This changes the existing message!</div>
  </template>
</turbo-stream>

When we click on Post any message button, the message that appear below that button will get replaced with the message that is mentioned in the app/views/other/post_something.turbo_stream.erb template

Stimulus

There are some cases in an application where JS is needed, therefore to cover those scenarios we require Hotwire JS tool. Hotwire has a JS tool because in some scenarios Turbo-* tools are not sufficient. But as we know that Hotwire is used to reduce the usage of JS in an application, Stimulus considers HTML as the single source of truth. Consider the case where we have to give elements on a page some JavaScript attributes, such as data controller, data-action, and data target. For that, a stimulus controller that can access elements and receive events based on those characteristics will be created.

Make a change in app/views/other/index.html.erb template file in rails application

#CODE

<h1>This is Another page</h1>
<div><%= link_to "Enter to home page", root_path %></div>

<div style="margin-top: 2rem;">
  <%= form_with scope: :any, url: post_something_path do |form| %>
      <%= form.submit 'Post something' %>
  <% end %>
  <turbo-frame id="messages">
    <div>An empty message</div>
  </turbo-frame>
</div>

<div style="margin-top: 2rem;">
  <h2>Stimulus</h2>  
  <div data-controller="hello">
    <input data-hello-target="name" type="text">
    <button data-action="click->hello#greet">
      Greet
    </button>
    <span data-hello-target="output">
    </span>
  </div>
</div>

Make changes in the hello_controller.js in path app/JavaScript/controllers and add a stimulus controller in the file, which helps to bring the HTML into life.

#CODE

import { Controller } from "@hotwired/stimulus"

export default class extends Controller {
  static targets = [ "name", "output" ]

  greet() {
    this.outputTarget.textContent =
      `Hello, ${this.nameTarget.value}!`
  }
}

Go to your browser after making the changes in the code and click on Enter to other page link which will navigate to the localhost:3000/other/index page there you can see the changes implemented by the stimulus controller that is designed to augment your HTML with just enough behavior to make it more responsive.

With just a little bit of work, Turbo and Stimulus together offer a complete answer for applications that are quick and compelling.

Using Rails 7 Hotwire helps to load the pages at a faster speed and allows you to render templates on the server, where you have access to your whole domain model. It is a productive development experience in ROR, without compromising any of the speed or responsiveness associated with SPA.

Conclusion

We hope you were satisfied with our Rails Hotwire tutorial. Write to us at service@bacancy.com for any query that you want to resolve, or if you want us to share a tutorial on your query.

For more such solutions on RoR, check out our Ruby on Rails Tutorials. We will always strive to amaze you and cater to your needs.

Original article source at: https://www.bacancytechnology.com/

#rails #ruby 

Pdf2gerb: Perl Script Converts PDF Files to Gerber format

pdf2gerb

Perl script converts PDF files to Gerber format

Pdf2Gerb generates Gerber 274X photoplotting and Excellon drill files from PDFs of a PCB. Up to three PDFs are used: the top copper layer, the bottom copper layer (for 2-sided PCBs), and an optional silk screen layer. The PDFs can be created directly from any PDF drawing software, or a PDF print driver can be used to capture the Print output if the drawing software does not directly support output to PDF.

The general workflow is as follows:

1. Design the PCB using your favorite CAD or drawing software.
2. Print the top and bottom copper and top silk screen layers to a PDF file.
3. Run Pdf2Gerb on the PDFs to create Gerber and Excellon files.
4. Use a Gerber viewer to double-check the output against the original PCB design.
5. Make adjustments as needed.
6. Submit the files to a PCB manufacturer.

Please note that Pdf2Gerb does NOT perform DRC (Design Rule Checks), as these will vary according to individual PCB manufacturer conventions and capabilities. Also note that Pdf2Gerb is not perfect, so the output files must always be checked before submitting them. As of version 1.6, Pdf2Gerb supports most PCB elements, such as round and square pads, round holes, traces, SMD pads, ground planes, no-fill areas, and panelization. However, because it interprets the graphical output of a Print function, there are limitations in what it can recognize (or there may be bugs).

See docs/Pdf2Gerb.pdf for install/setup, config, usage, and other info.

---

pdf2gerb_cfg.pm

#Pdf2Gerb config settings:
#Put this file in same folder/directory as pdf2gerb.pl itself (global settings),
#or copy to another folder/directory with PDFs if you want PCB-specific settings.
#There is only one user of this file, so we don't need a custom package or namespace.
#NOTE: all constants defined in here will be added to main namespace.
#package pdf2gerb_cfg;

use strict; #trap undef vars (easier debug)
use warnings; #other useful info (easier debug)


##############################################################################################
#configurable settings:
#change values here instead of in main pfg2gerb.pl file

use constant WANT_COLORS => ($^O !~ m/Win/); #ANSI colors no worky on Windows? this must be set < first DebugPrint() call

#just a little warning; set realistic expectations:
#DebugPrint("${\(CYAN)}Pdf2Gerb.pl ${\(VERSION)}, $^O O/S\n${\(YELLOW)}${\(BOLD)}${\(ITALIC)}This is EXPERIMENTAL software.  \nGerber files MAY CONTAIN ERRORS.  Please CHECK them before fabrication!${\(RESET)}", 0); #if WANT_DEBUG

use constant METRIC => FALSE; #set to TRUE for metric units (only affect final numbers in output files, not internal arithmetic)
use constant APERTURE_LIMIT => 0; #34; #max #apertures to use; generate warnings if too many apertures are used (0 to not check)
use constant DRILL_FMT => '2.4'; #'2.3'; #'2.4' is the default for PCB fab; change to '2.3' for CNC

use constant WANT_DEBUG => 0; #10; #level of debug wanted; higher == more, lower == less, 0 == none
use constant GERBER_DEBUG => 0; #level of debug to include in Gerber file; DON'T USE FOR FABRICATION
use constant WANT_STREAMS => FALSE; #TRUE; #save decompressed streams to files (for debug)
use constant WANT_ALLINPUT => FALSE; #TRUE; #save entire input stream (for debug ONLY)

#DebugPrint(sprintf("${\(CYAN)}DEBUG: stdout %d, gerber %d, want streams? %d, all input? %d, O/S: $^O, Perl: $]${\(RESET)}\n", WANT_DEBUG, GERBER_DEBUG, WANT_STREAMS, WANT_ALLINPUT), 1);
#DebugPrint(sprintf("max int = %d, min int = %d\n", MAXINT, MININT), 1); 

#define standard trace and pad sizes to reduce scaling or PDF rendering errors:
#This avoids weird aperture settings and replaces them with more standardized values.
#(I'm not sure how photoplotters handle strange sizes).
#Fewer choices here gives more accurate mapping in the final Gerber files.
#units are in inches
use constant TOOL_SIZES => #add more as desired
(
#round or square pads (> 0) and drills (< 0):
    .010, -.001,  #tiny pads for SMD; dummy drill size (too small for practical use, but needed so StandardTool will use this entry)
    .031, -.014,  #used for vias
    .041, -.020,  #smallest non-filled plated hole
    .051, -.025,
    .056, -.029,  #useful for IC pins
    .070, -.033,
    .075, -.040,  #heavier leads
#    .090, -.043,  #NOTE: 600 dpi is not high enough resolution to reliably distinguish between .043" and .046", so choose 1 of the 2 here
    .100, -.046,
    .115, -.052,
    .130, -.061,
    .140, -.067,
    .150, -.079,
    .175, -.088,
    .190, -.093,
    .200, -.100,
    .220, -.110,
    .160, -.125,  #useful for mounting holes
#some additional pad sizes without holes (repeat a previous hole size if you just want the pad size):
    .090, -.040,  #want a .090 pad option, but use dummy hole size
    .065, -.040, #.065 x .065 rect pad
    .035, -.040, #.035 x .065 rect pad
#traces:
    .001,  #too thin for real traces; use only for board outlines
    .006,  #minimum real trace width; mainly used for text
    .008,  #mainly used for mid-sized text, not traces
    .010,  #minimum recommended trace width for low-current signals
    .012,
    .015,  #moderate low-voltage current
    .020,  #heavier trace for power, ground (even if a lighter one is adequate)
    .025,
    .030,  #heavy-current traces; be careful with these ones!
    .040,
    .050,
    .060,
    .080,
    .100,
    .120,
);
#Areas larger than the values below will be filled with parallel lines:
#This cuts down on the number of aperture sizes used.
#Set to 0 to always use an aperture or drill, regardless of size.
use constant { MAX_APERTURE => max((TOOL_SIZES)) + .004, MAX_DRILL => -min((TOOL_SIZES)) + .004 }; #max aperture and drill sizes (plus a little tolerance)
#DebugPrint(sprintf("using %d standard tool sizes: %s, max aper %.3f, max drill %.3f\n", scalar((TOOL_SIZES)), join(", ", (TOOL_SIZES)), MAX_APERTURE, MAX_DRILL), 1);

#NOTE: Compare the PDF to the original CAD file to check the accuracy of the PDF rendering and parsing!
#for example, the CAD software I used generated the following circles for holes:
#CAD hole size:   parsed PDF diameter:      error:
#  .014                .016                +.002
#  .020                .02267              +.00267
#  .025                .026                +.001
#  .029                .03167              +.00267
#  .033                .036                +.003
#  .040                .04267              +.00267
#This was usually ~ .002" - .003" too big compared to the hole as displayed in the CAD software.
#To compensate for PDF rendering errors (either during CAD Print function or PDF parsing logic), adjust the values below as needed.
#units are pixels; for example, a value of 2.4 at 600 dpi = .0004 inch, 2 at 600 dpi = .0033"
use constant
{
    HOLE_ADJUST => -0.004 * 600, #-2.6, #holes seemed to be slightly oversized (by .002" - .004"), so shrink them a little
    RNDPAD_ADJUST => -0.003 * 600, #-2, #-2.4, #round pads seemed to be slightly oversized, so shrink them a little
    SQRPAD_ADJUST => +0.001 * 600, #+.5, #square pads are sometimes too small by .00067, so bump them up a little
    RECTPAD_ADJUST => 0, #(pixels) rectangular pads seem to be okay? (not tested much)
    TRACE_ADJUST => 0, #(pixels) traces seemed to be okay?
    REDUCE_TOLERANCE => .001, #(inches) allow this much variation when reducing circles and rects
};

#Also, my CAD's Print function or the PDF print driver I used was a little off for circles, so define some additional adjustment values here:
#Values are added to X/Y coordinates; units are pixels; for example, a value of 1 at 600 dpi would be ~= .002 inch
use constant
{
    CIRCLE_ADJUST_MINX => 0,
    CIRCLE_ADJUST_MINY => -0.001 * 600, #-1, #circles were a little too high, so nudge them a little lower
    CIRCLE_ADJUST_MAXX => +0.001 * 600, #+1, #circles were a little too far to the left, so nudge them a little to the right
    CIRCLE_ADJUST_MAXY => 0,
    SUBST_CIRCLE_CLIPRECT => FALSE, #generate circle and substitute for clip rects (to compensate for the way some CAD software draws circles)
    WANT_CLIPRECT => TRUE, #FALSE, #AI doesn't need clip rect at all? should be on normally?
    RECT_COMPLETION => FALSE, #TRUE, #fill in 4th side of rect when 3 sides found
};

#allow .012 clearance around pads for solder mask:
#This value effectively adjusts pad sizes in the TOOL_SIZES list above (only for solder mask layers).
use constant SOLDER_MARGIN => +.012; #units are inches

#line join/cap styles:
use constant
{
    CAP_NONE => 0, #butt (none); line is exact length
    CAP_ROUND => 1, #round cap/join; line overhangs by a semi-circle at either end
    CAP_SQUARE => 2, #square cap/join; line overhangs by a half square on either end
    CAP_OVERRIDE => FALSE, #cap style overrides drawing logic
};
    
#number of elements in each shape type:
use constant
{
    RECT_SHAPELEN => 6, #x0, y0, x1, y1, count, "rect" (start, end corners)
    LINE_SHAPELEN => 6, #x0, y0, x1, y1, count, "line" (line seg)
    CURVE_SHAPELEN => 10, #xstart, ystart, x0, y0, x1, y1, xend, yend, count, "curve" (bezier 2 points)
    CIRCLE_SHAPELEN => 5, #x, y, 5, count, "circle" (center + radius)
};
#const my %SHAPELEN =
#Readonly my %SHAPELEN =>
our %SHAPELEN =
(
    rect => RECT_SHAPELEN,
    line => LINE_SHAPELEN,
    curve => CURVE_SHAPELEN,
    circle => CIRCLE_SHAPELEN,
);

#panelization:
#This will repeat the entire body the number of times indicated along the X or Y axes (files grow accordingly).
#Display elements that overhang PCB boundary can be squashed or left as-is (typically text or other silk screen markings).
#Set "overhangs" TRUE to allow overhangs, FALSE to truncate them.
#xpad and ypad allow margins to be added around outer edge of panelized PCB.
use constant PANELIZE => {'x' => 1, 'y' => 1, 'xpad' => 0, 'ypad' => 0, 'overhangs' => TRUE}; #number of times to repeat in X and Y directions

# Set this to 1 if you need TurboCAD support.
#$turboCAD = FALSE; #is this still needed as an option?

#CIRCAD pad generation uses an appropriate aperture, then moves it (stroke) "a little" - we use this to find pads and distinguish them from PCB holes. 
use constant PAD_STROKE => 0.3; #0.0005 * 600; #units are pixels
#convert very short traces to pads or holes:
use constant TRACE_MINLEN => .001; #units are inches
#use constant ALWAYS_XY => TRUE; #FALSE; #force XY even if X or Y doesn't change; NOTE: needs to be TRUE for all pads to show in FlatCAM and ViewPlot
use constant REMOVE_POLARITY => FALSE; #TRUE; #set to remove subtractive (negative) polarity; NOTE: must be FALSE for ground planes

#PDF uses "points", each point = 1/72 inch
#combined with a PDF scale factor of .12, this gives 600 dpi resolution (1/72 * .12 = 600 dpi)
use constant INCHES_PER_POINT => 1/72; #0.0138888889; #multiply point-size by this to get inches

# The precision used when computing a bezier curve. Higher numbers are more precise but slower (and generate larger files).
#$bezierPrecision = 100;
use constant BEZIER_PRECISION => 36; #100; #use const; reduced for faster rendering (mainly used for silk screen and thermal pads)

# Ground planes and silk screen or larger copper rectangles or circles are filled line-by-line using this resolution.
use constant FILL_WIDTH => .01; #fill at most 0.01 inch at a time

# The max number of characters to read into memory
use constant MAX_BYTES => 10 * M; #bumped up to 10 MB, use const

use constant DUP_DRILL1 => TRUE; #FALSE; #kludge: ViewPlot doesn't load drill files that are too small so duplicate first tool

my $runtime = time(); #Time::HiRes::gettimeofday(); #measure my execution time

print STDERR "Loaded config settings from '${\(__FILE__)}'.\n";
1; #last value must be truthful to indicate successful load


#############################################################################################
#junk/experiment:

#use Package::Constants;
#use Exporter qw(import); #https://perldoc.perl.org/Exporter.html

#my $caller = "pdf2gerb::";

#sub cfg
#{
#    my $proto = shift;
#    my $class = ref($proto) || $proto;
#    my $settings =
#    {
#        $WANT_DEBUG => 990, #10; #level of debug wanted; higher == more, lower == less, 0 == none
#    };
#    bless($settings, $class);
#    return $settings;
#}

#use constant HELLO => "hi there2"; #"main::HELLO" => "hi there";
#use constant GOODBYE => 14; #"main::GOODBYE" => 12;

#print STDERR "read cfg file\n";

#our @EXPORT_OK = Package::Constants->list(__PACKAGE__); #https://www.perlmonks.org/?node_id=1072691; NOTE: "_OK" skips short/common names

#print STDERR scalar(@EXPORT_OK) . " consts exported:\n";
#foreach(@EXPORT_OK) { print STDERR "$_\n"; }
#my $val = main::thing("xyz");
#print STDERR "caller gave me $val\n";
#foreach my $arg (@ARGV) { print STDERR "arg $arg\n"; }

---

Download Details:

Author: swannman
Source Code: https://github.com/swannman/pdf2gerb

License: GPL-3.0 license

#perl 

Static Code Analysis: What It Is? How to Use It?

Static code analysis refers to the technique of approximating the runtime behavior of a program. In other words, it is the process of predicting the output of a program without actually executing it.

Lately, however, the term “Static Code Analysis” is more commonly used to refer to one of the applications of this technique rather than the technique itself — program comprehension — understanding the program and detecting issues in it (anything from syntax errors to type mismatches, performance hogs likely bugs, security loopholes, etc.). This is the usage we’d be referring to throughout this post.

“The refinement of techniques for the prompt discovery of error serves as well as any other as a hallmark of what we mean by science.”

• J. Robert Oppenheimer

Outline

We cover a lot of ground in this post. The aim is to build an understanding of static code analysis and to equip you with the basic theory, and the right tools so that you can write analyzers on your own.

We start our journey with laying down the essential parts of the pipeline which a compiler follows to understand what a piece of code does. We learn where to tap points in this pipeline to plug in our analyzers and extract meaningful information. In the latter half, we get our feet wet, and write four such static analyzers, completely from scratch, in Python.

Note that although the ideas here are discussed in light of Python, static code analyzers across all programming languages are carved out along similar lines. We chose Python because of the availability of an easy to use ast module, and wide adoption of the language itself.

How does it all work?

Before a computer can finally “understand” and execute a piece of code, it goes through a series of complicated transformations:

As you can see in the diagram (go ahead, zoom it!), the static analyzers feed on the output of these stages. To be able to better understand the static analysis techniques, let’s look at each of these steps in some more detail:

Scanning

The first thing that a compiler does when trying to understand a piece of code is to break it down into smaller chunks, also known as tokens. Tokens are akin to what words are in a language.

A token might consist of either a single character, like (, or literals (like integers, strings, e.g., 7, Bob, etc.), or reserved keywords of that language (e.g, def in Python). Characters which do not contribute towards the semantics of a program, like trailing whitespace, comments, etc. are often discarded by the scanner.

Python provides the tokenize module in its standard library to let you play around with tokens:

Python

1

import io

2

import tokenize

3

4

code = b"color = input('Enter your favourite color: ')"

5

6

for token in tokenize.tokenize(io.BytesIO(code).readline):

7

    print(token)

Python

1

TokenInfo(type=62 (ENCODING),  string='utf-8')

2

TokenInfo(type=1  (NAME),      string='color')

3

TokenInfo(type=54 (OP),        string='=')

4

TokenInfo(type=1  (NAME),      string='input')

5

TokenInfo(type=54 (OP),        string='(')

6

TokenInfo(type=3  (STRING),    string="'Enter your favourite color: '")

7

TokenInfo(type=54 (OP),        string=')')

8

TokenInfo(type=4  (NEWLINE),   string='')

9

TokenInfo(type=0  (ENDMARKER), string='')

(Note that for the sake of readability, I’ve omitted a few columns from the result above — metadata like starting index, ending index, a copy of the line on which a token occurs, etc.)

#code quality #code review #static analysis #static code analysis #code analysis #static analysis tools #code review tips #static code analyzer #static code analysis tool #static analyzer

How to Use Of Not Equal To The Operator in Bash

Many types of operators exist in Bash to check the equality or inequality of two strings or numbers. The “-ne” and “!=” operators are used to check the inequality of two values in Bash. The single third brackets ([ ]) are used in the “if” condition when the “!=” operator is used to check the inequality. The double third brackets ([[ ]]) are used in the “if” condition when the “-ne” operator is used to check the inequality. The methods of comparing the string and numeric values using these operators are shown in this tutorial.

Using the “!=” Operator

The “!=” operator can be used to check the inequality between two numeric values or two string values. Two uses of this operator are shown in the following examples.

Example 1: Checking the Inequality Between Numbers
Create a Bash file with the following script that takes a number input and check whether the input value is equal to 10 or not using the “!=” operator. The single third brackets ([ ]) are used in the “if” condition here.

#!/bin/bash
#Take a number
echo -n "Enter a number:"
read number

#Use '!=' operator to check the number value
if [ $number != 10 ]; then
    echo "The number is not equal to 10."
else
    echo "The number is equal to 10."
fi

The script is executed twice in the following output. Twelve (12) is taken as input in the first execution and “The number is not equal to 10” is printed. Ten (10) is taken as input in the second execution and “The number is equal to 10” is printed:

Example 2:
Create a Bash file with the following script that takes two string values and check whether the input values are equal or not using the “!=” operator. The single third brackets ([ ]) are used in the “if” condition here.

#!/bin/bash
#Take a number
echo -n "Enter the first string value: "
read str1
echo -n "Enter the second string value: "
read str2

#Use '!=' operator to check the string values
if [ "$str1" != "$str2" ]; then
    echo "The strings are not equal."
else
    echo "The strings are equal."
fi

The script is executed twice in the following output. The “Hello” and “hello” string values are taken as inputs in the first execution and these values are not equal because the string values are compared case-sensitively. In the next execution, the “hello” and “hello” string values are taken as equal inputs:

Using the “-ne” Operator

The “-ne” operator can be used to check the inequality between two numeric values but not can be used to compare the string values. Two uses of this operator to compare the numeric and string values are shown in the following examples.

Example 1:
Create a Bash file with the following script that takes the username as input. Next, the length of the input value is counted after removing the newline(\n) character. Whether the length of the username is equal to 8 or not is checked using the “-ne” operator. The double third brackets ([[ ]]) are used in the “if” condition here.

#!/bin/bash
#Take the username
echo -n "Enter username: "
read username

#Remove newline from the input value
username=`echo $username | tr -d '\n'`
#Count the total character
len=${#username}

#Use the '-ne' operator to check the number value
if [[ $len -ne 8 ]]; then
    echo "Username must be 8 characters long."
else
    echo "Username: $username"
fi

The script is executed twice in the following output. The “admin” is taken as input in the first execution and the “Username must be 8 characters long” is printed. The “durjoy23” is taken as input in the second execution and the “Username: durjoy23” is printed:

Example 2:
Create a Bash file with the following script that takes the username as input. Next, whether the input value is equal to “admin” or not is checked using the “-ne” operator. The double third brackets ([[ ]]) are used in the “if” condition here. The “-ne” operator does not work to compare two string values.

#!/bin/bash
#Take the username and password
echo -n "Enter username: "
read username

#Remove newline from the input value
username=`echo $username | tr -d '\n'`

#Use '-ne' operator to check the string values
if [[ "$username" -ne "admin" ]]; then
    echo "Invalid user."
else
    echo "Valid user."
fi

The script is executed twice in the following output. The “if” condition is returned true in both executions for the valid and invalid outputs which is a “wrong” output:

Conclusion

The method of comparing two values using the “!=” and “-ne” operators are shown in this tutorial using multiple examples to know the uses of these operators properly.

Original article source at: https://linuxhint.com/

#bash #equal #operator 

How To Create Tabs in Less Than 12 Minutes Using HTML CSS

In this video, We have created a Tab design in HTML and CSS without using JavaScript. I have also provided HTML and CSS code on my website, you can visit my website by clicking given link. 

Subscribe: https://www.youtube.com/@CodingLabYT/featured 

Source Code :

HTML :

<!DOCTYPE html>
<html lang="en" dir="ltr">
  <head>
    <meta charset="UTF-8">
    <!--<title> CSS Vertical Tabs </title>-->
    <link rel="stylesheet" href="style.css">
    <!-- Fontawesome CDN Link -->
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.15.2/css/all.min.css"/>
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
   </head>
<body>
  <div class="container">
    <div class="topic">CSS Vertical Tabs.</div>
    <div class="content">
      <input type="radio" name="slider" checked id="home">
      <input type="radio" name="slider" id="blog">
      <input type="radio" name="slider" id="help">
      <input type="radio" name="slider" id="code">
      <input type="radio" name="slider" id="about">
      <div class="list">
        <label for="home" class="home">
        <i class="fas fa-home"></i>
        <span class="title">Home</span>
      </label>
      <label for="blog" class="blog">
        <span class="icon"><i class="fas fa-blog"></i></span>
        <span class="title">Blog</span>
      </label>
      <label for="help" class="help">
        <span class="icon"><i class="far fa-envelope"></i></span>
        <span class="title">Help</span>
      </label>
      <label for="code" class="code">
        <span class="icon"><i class="fas fa-code"></i></span>
        <span class="title">Code</span>
      </label>
      <label for="about" class="about">
        <span class="icon"><i class="far fa-user"></i></span>
        <span class="title">About</span>
      </label>
      <div class="slider"></div>
    </div>
      <div class="text-content">
        <div class="home text">
          <div class="title">Home Content</div>
          <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quasi excepturi ducimus sequi dignissimos expedita tempore omnis quos cum, possimus, aspernatur esse nihil commodi est maiores dolorum rem iusto atque, beatae voluptas sit eligendi architecto dolorem temporibus. Non magnam ipsam, voluptas quasi nam dicta ut. Ad corrupti aliquid obcaecati alias, nemo veritatis porro nisi eius sequi dignissimos ea repellendus quibusdam minima ipsum animi quae, libero quisquam a! Laudantium iste est sapiente, ullam itaque odio iure laborum voluptatem quaerat tempore doloremque quam modi, atque minima enim saepe! Dolorem rerum minima incidunt, officia!</p>
        </div>
        <div class="blog text">
          <div class="title">Blog Content</div>
          <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Alias tempora, unde reprehenderit incidunt excepturi blanditiis ullam dignissimos provident quam? Fugit, enim! Architecto ad officiis dignissimos ex quae iusto amet pariatur, ea eius aut velit, tempora magnam hic autem maiores unde corrupti tenetur delectus! Voluptatum praesentium labore consectetur ea qui illum illo distinctio, sunt, ipsam rerum optio quibusdam cum a? Aut facilis non fuga molestiae voluptatem omnis reprehenderit, dignissimos commodi repellat sapiente natus ipsam, ipsa distinctio. Ducimus repudiandae fuga aliquid, numquam.</p>
        </div>
        <div class="help text">
          <div class="title">Help Content</div>
          <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Maiores error neque, officia excepturi dolores quis dolor, architecto iusto deleniti a soluta nostrum. Fuga reiciendis beatae, dicta voluptatem, vitae eligendi maxime accusamus. Amet totam aut odio velit cumque autem neque sequi provident mollitia, nisi sunt maiores facilis debitis in officiis asperiores saepe quo soluta laudantium ad non quisquam! Repellendus culpa necessitatibus aliquam quod mollitia perspiciatis ducimus doloribus perferendis autem, omnis, impedit, veniam qui dolorem? Ipsam nihil assumenda, sit ratione blanditiis eius aliquam libero iusto, dolorum aut perferendis modi laboriosam sint dolor.</p>
        </div>
        <div class="code text">
          <div class="title">Code Content</div>
          <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Tempore magnam vitae inventore blanditiis nam tenetur voluptates doloribus error atque reprehenderit, necessitatibus minima incidunt a eius corrupti placeat, quasi similique deserunt, harum? Quia ut impedit ab earum expedita soluta repellat perferendis hic tempora inventore, accusantium porro consequuntur quisquam et assumenda distinctio dignissimos doloremque enim nemo delectus deserunt! Ullam perspiciatis quae aliquid animi quam amet deleniti, at dolorum tenetur, tempore laborum.</p>
        </div>
        <div class="about text">
          <div class="title">About Content</div>
          <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Necessitatibus incidunt possimus quas ad, sit nam veniam illo ullam sapiente, aspernatur fugiat atque. Laboriosam libero voluptatum molestiae veniam earum quisquam, laudantium aperiam, eligendi dicta animi maxime sunt non nisi, ex, ipsa! Soluta ex, quibusdam voluptatem distinctio asperiores recusandae veritatis optio dolorem illo nesciunt quos ullam, dicta numquam ipsam cumque sed. Blanditiis omnis placeat, enim sit dicta eligendi voluptatibus laborum consectetur repudiandae tempora numquam molestiae rerum mollitia nemo. Velit perspiciatis, nesciunt, quo illo quas error debitis molestiae et sapiente neque tempore natus?</p>
        </div>
      </div>
    </div>
  </div>

</body>
</html>

CSS :

@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@200;300;400;500;600;700&display=swap');
*{
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Poppins', sans-serif;
}
body{
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #dad3f8;
}
::selection{
  background: #6d50e2;
  color: #fff;
}
.container{
  max-width: 950px;
  width: 100%;
  padding: 40px 50px  40px  40px;
  background: #fff;
  margin: 0 20px;
  border-radius: 12px;
  box-shadow: 0 5px 10px rgba(0, 0, 0, 0.2);
}
.container .topic{
  font-size: 30px;
  font-weight: 500;
  margin-bottom: 20px;
}
.content{
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.content .list{
  display: flex;
  flex-direction: column;
  width: 20%;
  margin-right: 50px;
  position: relative;
}
.content .list label{
  height: 60px;
  font-size: 22px;
  font-weight: 500;
  line-height: 60px;
  cursor: pointer;
  padding-left: 25px;
  transition: all 0.5s ease;
  color: #333;
  z-index: 12;
}
#home:checked ~ .list label.home,
#blog:checked ~ .list label.blog,
#help:checked ~ .list label.help,
#code:checked ~ .list label.code,
#about:checked ~ .list label.about{
  color: #fff;
}
.content .list label:hover{
  color: #6d50e2;
}
.content .slider{
  position: absolute;
  left: 0;
  top: 0;
  height: 60px;
  width: 100%;
  border-radius: 12px;
  background: #6d50e2;
  transition: all 0.4s ease;
}
#home:checked ~ .list .slider{
  top: 0;
}
#blog:checked ~ .list .slider{
  top: 60px;
}
#help:checked ~ .list .slider{
  top: 120px;
}
#code:checked ~ .list .slider{
  top: 180px;
}
#about:checked ~ .list .slider{
  top: 240px;
}
.content .text-content{
  width: 80%;
  height: 100%;
}
.content .text{
  display: none;
}
.content .text .title{
  font-size: 25px;
  margin-bottom: 10px;
  font-weight: 500;
}
.content .text p{
  text-align: justify;
}
.content .text-content .home{
  display: block;
}
#home:checked ~ .text-content .home,
#blog:checked ~ .text-content .blog,
#help:checked ~ .text-content .help,
#code:checked ~ .text-content .code,
#about:checked ~ .text-content .about{
  display: block;
}
#blog:checked ~ .text-content .home,
#help:checked ~ .text-content .home,
#code:checked ~ .text-content .home,
#about:checked ~ .text-content .home{
  display: none;
}
.content input{
  display: none;
}

Download Code Files

#javascript #html #css