A base library for functional programming in deno

prelude

a base library for functional programming in deno

Roadmap

⚠️ WATCH OUT!

  • semver won’t be enforced until v1.0.0
  • partial application and other tuple related functions won’t be available until deno supports TypeScript 4.0

Goals

  • provide interfaces corresponding to static-land spec type classes and factory functions for implementing its instances
  • provide a good replacement for libraries like fp-ts, ramda, hkts and lodash
  • provide interfaces for additional purescript based type classes
  • provide some basic (primitives, Maybe, Either, etc…) instances for existing type classes
  • support and idioms for deno comes first, but browser and node should be compatible

Non-Goals

  • break compatibility with static-land
  • provide every type class and instance corresponding to haskell/purescript
  • requiring abstractions with higher runtime cost than handwritten functional code

Documentation

Is currently a work in progress and not a priority until instances for most primitive types are implemented.

Known limitations

  • every kind is limited to a single parameter (but kinds can yield kinds)
  • testing kind applications is weird
  • a useless expression is required to check type class instances:
(():
  & Monoid<Ap<ArrayKind, unknown>>
  & Setoid<Ap<ArrayKind, unknown>>
  & Semigroup<Ap<ArrayKind, unknown>>
  & Group<Ap<ArrayKind, unknown>>
  & Functor<ArrayKind>
  & Foldable<ArrayKind>
  & Filterable<ArrayKind>
  & Apply<ArrayKind>
  & Applicative<ArrayKind>
  & Chain<ArrayKind>
  & Monad<ArrayKind> => ({
  equals,
  empty,
  concat,
  map,
  reduce,
  filter,
  ap,
  of,
  chain,
  join,
  invert,
}));

Related work

For Developers

If you want to contribute to prelude:

  1. clone this repository
  2. make sure you have deno installed in your path
  3. install the pre-commit running:
    • on linux/unix-likes: ./scripts/hook from the repository root directory
    • on windows with cmder: sh scripts/hook from the repository root directory
  4. run scripts from the repository root directory

Thanks!

Download Details:

Author: kress95

Source Code: https://github.com/kress95/prelude

#deno #nodejs #node #javascript

What is GEEK

Buddha Community

A base library for functional programming in deno
Angela  Dickens

Angela Dickens

1595593200

Functional Programming

Functional Programming is a Declarative style of Programming Paradigm for writing computer programs.
But, What are Functions ?
Functions in general, applies computation on given input and returns the output. It relates input to an output.
f(x) = x + 2;
f(1) = 1 + 2 = 3;
f(2) = 2 + 2 = 4;
Above mentioned is a simple function that adds 2 to the input value and returns output. It relates value [1,2] => [3,4]. Similarly, a function in computer programming is a block of instruction that performs computation on given input and returns the output.
Functional Programming is such a style of writing computer programs using these tiny functions that works together and perform required computation.
Functions in Functional Programming
The philosophy of functional programming is to maintain certain characteristics while writing functions in a computer program. These characteristics are the fundamental nature of functional programming that describe what shall be the behaviour of a function. These are as follows :
Declarative
A function must be declarative, it simply tells what to compute, without specifying how to compute it.
f(x) = x * 4; 👍
Declarative function that tells to multiply input by 4;
f(x) = { y = x + x; z = x + x; return y + z;} 👎
Non-Declarative function that specify how to multiply input by 4;
Pure
A function must give the same output for a given input value, at any period of time. It is not dependent upon anything outside the function definition.
f(x) = It’s never too late; 👍
Pure function that will always return It’s never too late
f(x) = If today’s Friday or Saturday then It’s never too late else It’s late. 👎
Impure function that consider day for returning value. The value is not predictable. It can change. So a function that performs anything which is unpredictable is not a pure function. The condition or the execution is dynamic or unfixed in an impure function.

#development #functional-programming #software #software-programming #declarative-programming #function

Are functions from programming really functions?

If you are reading this, then most probably you already know quite well what functions are in programming. A function is quite a common and spread programming construct that is present in almost all programming languages.

Generally, a function is a block of code that takes some parameters from outside, executes some operations in which these parameters may be used, then it returns an output value. Actually, in many programming languages functions are allowed to not return something or to return multiple values, not only one. But these cases can be also be represented, for the sake of generality, as only one value. For the “no return” case we can use a special value to represent that (in Python that special value is None; whenever you don’t return something from a function it’s returned None). And for the case of more values, we can use a vector of multiple values as a single object.

For example, in Python a function definition looks like this:

def func_name(param1, param2, ...):

    ## do some stuff with input parameters
    return output_value

Now, the question I want to ask: Are these functions from programming true mathematical functions?

Well…, let’s first recall what a mathematical function is.

In mathematics, a function is just a mapping from a set A to a set B, in which any element from A has only one associated element in B.

#python #programming #function #mathematics #functional-programming

Tia  Gottlieb

Tia Gottlieb

1596300660

Functional Programming Series (2): What Is a Monoid?

For those interested in functional programming, I’ll talk about monoids and why they’re very important to understand ahead of time.

Don’t get confused: This isn’t monad — it’s monoid. I’m pretty sure you already know of monoids and you use them almost every day — you just didn’t know the term for them.


Prior to Reading

This is a series on functional programming, so you might not understand what this article is going to talk about if you haven’t read the previous posts.

You can check out other posts related to this topic


Identity Function

Let’s assume there’s a function named identity that takes A and returns A.

const identity: <A>(a: A): A => a;

interface Student {
  name: string;
  age: number;
}
identity<number>(3) // 3
identity<string>('hello') // hello
identity<Student>({ 
  name: 'Bincent',
  age: 5
}); // { name: 'Bincent', age: 5 }

In functional programming, this useless function (seems useless) is an important factor for many other concepts (such as monoids) that we’re about to talk about.

Image for post

Basically, a monoid is a set of elements that holds the rules of the semigroup and the identity-element rule.

If S is a set of elements, a is a member of S, and · is a proper binary operation, a·e = e·a ∈ S must be satisfied to be a monoid.

Identity: a ∈ S, a·e = e·a = a ∈ S

Some documentation calls this using the number 1 and the any alphabet in subscript — for example, 1x referring to the identity on the variable x. Or some documentation uses just a single alphabet letter, such as or e.

That’s all there is to know about monoids, let’s practice with some simple examples.

#typescript #programming #functional-programming #javascript #coding #function

Let’s Talk Functional Programming

Most of what I will discuss in this article is knowledge accumulated from reading, “Functional Programming in JavaScript”, by Luis Atencio. Let’s dig right in…

What is functional programming?

In simple terms, functional programming is a software development style that places a major emphasis on the use of functions. You might say, “Well, I already use functions daily, what’s the difference?” Well, it’s not a matter of just applying functions to come up with a result. The goal, rather, is to abstract control flows and operations on data with functions in order to avoid side effects and reduce mutation of state in your application.

#programming #javascript #functional #web-development #functional-programming

Vincent Lab

Vincent Lab

1605017502

The Difference Between Regular Functions and Arrow Functions in JavaScript

Other then the syntactical differences. The main difference is the way the this keyword behaves? In an arrow function, the this keyword remains the same throughout the life-cycle of the function and is always bound to the value of this in the closest non-arrow parent function. Arrow functions can never be constructor functions so they can never be invoked with the new keyword. And they can never have duplicate named parameters like a regular function not using strict mode.

Here are a few code examples to show you some of the differences
this.name = "Bob";

const person = {
name: “Jon”,

<span style="color: #008000">// Regular function</span>
func1: <span style="color: #0000ff">function</span> () {
    console.log(<span style="color: #0000ff">this</span>);
},

<span style="color: #008000">// Arrow function</span>
func2: () =&gt; {
    console.log(<span style="color: #0000ff">this</span>);
}

}

person.func1(); // Call the Regular function
// Output: {name:“Jon”, func1:[Function: func1], func2:[Function: func2]}

person.func2(); // Call the Arrow function
// Output: {name:“Bob”}

The new keyword with an arrow function
const person = (name) => console.log("Your name is " + name);
const bob = new person("Bob");
// Uncaught TypeError: person is not a constructor

If you want to see a visual presentation on the differences, then you can see the video below:

#arrow functions #javascript #regular functions #arrow functions vs normal functions #difference between functions and arrow functions