How can you write a parameterless function in Ramda using a point-free style?

Question

How can you write a parameterless function in Ramda using a point-free style?

Take a look at this functioning code snippet:

var randNum = x => () => Math.floor(x*Math.random());
var random10 = randNum(10)
times(random10, 10) // => [6, 3, 7, 0, 9, 1, 7, 2, 6, 0]

The function randNum creates a random number generator that will output an integer between 0 and N-1 when invoked. It serves as a factory for specific RNGs.

While experimenting with ramda.js and delving into functional programming concepts, I wondered if it's possible to refactor randNum into a point-free style using ramda?

One approach could be:

var unsuccessfulTry = pipe(multiply(Math.random()), Math.floor)

This implementation meets the "point-free style" criteria, but it diverges from the behavior of randNum: executing unsuccessfulTry(10) only results in a single random number instead of generating random numbers within the specified range each time it's called.

Despite numerous attempts, I haven't found the right combination of ramda functions to achieve a point-free rewrite. I'm unsure if this is due to my limitations or perhaps some intricacy related to utilizing random, which compromises referential transparency and might conflict with a point-free approach.

Update

Following discussions with Denys, here's a slight modification to the solution I came up with:

randNum = pipe(always, of, append(Math.random), useWith(pipe(multiply, Math.floor)), partial(__,[1,1]))

javascript functional-programming ramda.js

Answer 1

Answer №1

This function provides a helpful way to abstract another function in order to re-evaluate its arguments every time it is called.

thunk = fn => R.curryN(fn.length, (...args) => () => fn(...args))

The primary purpose of this new function is to trigger a side effect within the specified fn function.

With the introduction of the thunk function, we can create a function like randN as follows:

randN = thunk(R.pipe(S.S(R.multiply, Math.random), Math.floor))

R.times(randN(10), 5) // for example: [1, 6, 9, 4, 5]

Please note that S.S refers to the S combinator from Sanctuary, which essentially performs the same functionality as

R.converge(multiply, [Math.random, identity])

.

It is worth mentioning that adopting a point-free solution should only be considered if it truly enhances the clarity and readability of a function.

Answer 2

This function provides a helpful way to abstract another function in order to re-evaluate its arguments every time it is called.

thunk = fn => R.curryN(fn.length, (...args) => () => fn(...args))

The primary purpose of this new function is to trigger a side effect within the specified fn function.

With the introduction of the thunk function, we can create a function like randN as follows:

randN = thunk(R.pipe(S.S(R.multiply, Math.random), Math.floor))

R.times(randN(10), 5) // for example: [1, 6, 9, 4, 5]

Please note that S.S refers to the S combinator from Sanctuary, which essentially performs the same functionality as

R.converge(multiply, [Math.random, identity])

.

It is worth mentioning that adopting a point-free solution should only be considered if it truly enhances the clarity and readability of a function.

Answer 3

Answer №2

Exploring functional programming with a specific library can sometimes blur the lines between the unique characteristics of the library and the fundamental principles of the functional paradigm. However, in practical application, Ramda proves to be an invaluable tool, acting as a bridge between imperative programming and the abstract world of Fantasy Land in the realm of Javascript :D

Here is a manual approach:

// several versatile, reusable functions:
const comp = f => g => x => f(g(x)); // combining mathematical functions
const comp2 = comp(comp)(comp); // composition for binary functions
const flip = f => x => y => f(y)(x); // reversing arguments
const mul = y => x => x * y; // operator function

// constructing a point-free function:
const randN = comp2(Math.floor)(flip(comp(mul)(Math.random)));

let rand10 = randN(10); // generating random numbers
for (let i = 0; i < 10; i++) console.log(rand10());

It is important to note that randN is inherently impure due to the nature of random number generation being considered impure.

Answer 4

Exploring functional programming with a specific library can sometimes blur the lines between the unique characteristics of the library and the fundamental principles of the functional paradigm. However, in practical application, Ramda proves to be an invaluable tool, acting as a bridge between imperative programming and the abstract world of Fantasy Land in the realm of Javascript :D

Here is a manual approach:

// several versatile, reusable functions:
const comp = f => g => x => f(g(x)); // combining mathematical functions
const comp2 = comp(comp)(comp); // composition for binary functions
const flip = f => x => y => f(y)(x); // reversing arguments
const mul = y => x => x * y; // operator function

// constructing a point-free function:
const randN = comp2(Math.floor)(flip(comp(mul)(Math.random)));

let rand10 = randN(10); // generating random numbers
for (let i = 0; i < 10; i++) console.log(rand10());

It is important to note that randN is inherently impure due to the nature of random number generation being considered impure.

Answer 5

Answer №3

Create a function that generates an array of random numbers between 0 and 10 using Ramda library in JavaScript. The code snippet is as follows:

var randN = R.converge(R.partial, [R.wrap(R.pipe(R.converge(R.multiply, [Math.random, R.identity]), Math.floor), R.identity), R.of])
var rand10 = randN(10)
alert(R.times(rand10, 10)) // => [3, 1, 7, 5, 7, 5, 8, 4, 7, 2]

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.19.1/ramda.js"></script>

Answer 6

Create a function that generates an array of random numbers between 0 and 10 using Ramda library in JavaScript. The code snippet is as follows:

var randN = R.converge(R.partial, [R.wrap(R.pipe(R.converge(R.multiply, [Math.random, R.identity]), Math.floor), R.identity), R.of])
var rand10 = randN(10)
alert(R.times(rand10, 10)) // => [3, 1, 7, 5, 7, 5, 8, 4, 7, 2]

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.19.1/ramda.js"></script>

How can you write a parameterless function in Ramda using a point-free style?

Update

Answer №1

Answer №2

Answer №3

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