pipe any functions

[odoldotol]

Hi.

On this project,
would it be useful to be able to pipe any multiple functions?
regardless of whether they are synchronous or asynchronous.
even if there were errors in synchronous functions or rejections in asynchronous functions.

Using the Either monad concept makes it possible as follows.

---

Use Cases

For example, let’s consider three functions:

/**
 * Async function that accepts only even numbers;
 * throws an error for odd numbers
 */
const passEvenNumber = async (num: number) => {
  if (num % 2 === 0) {
    return num;
  } else {
    throw new Error(`passEvenNumber: ${num} is not even number`);
  }
};
  
/**
 * Asynchronous function that squares the number;
 * throws an error if the number is 0.
 */
const square = async (num: number) => {
  if (num === 0) {
    throw new Error(`square: 0 is not allowed`);
  } else {
    return num**2;
  }
};
  
/**
 * Synchronous function that subtracts 10;
 * throws an error if the result is 0 or below.
 */
const minus10 = (num: number) => {
  const result = num - 10;
  if (result <= 0) {
    throw new Error(`minus10: result(${result}) must be greater than 0`);
  } else {
    return result;
  }
};

Two of them are asynchronous, and the other one is synchronous.
All three functions can throw errors or be rejected.

Let`s do this.

import * as E from './either';
import * as F from '@fxts/core';

F.pipe(
  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
  F.toAsync,
  F.map(E.wrapAsync(passEvenNumber)),
  F.map(E.wrapFlatMapAsync(square)),
  F.map(E.wrapFlatMap(minus10)),
  F.concurrent(20),
  F.toArray
).then(console.log);

The console.log output is summarized briefly as follows.

[
  EitherLeft { reason: Error: square: 0 is not allowed },
  EitherLeft { reason: Error: passEvenNumber: 1 is not even number },
  EitherLeft { reason: Error: minus10: result(-6) must be greater than 0 },
  EitherLeft { reason: Error: passEvenNumber: 3 is not even number },
  EitherRight { value: 6 },
  EitherLeft { reason: Error: passEvenNumber: 5 is not even number },
  EitherRight { value: 26 },
  EitherLeft { reason: Error: passEvenNumber: 7 is not even number },
  EitherRight { value: 54 },
  EitherLeft { reason: Error: passEvenNumber: 9 is not even number },
  EitherRight { value: 90 }
]

---

I’d like to hear any thoughts on this.

Thank you.

[odoldotol]

Try this.

npm install @odoldotol/either

https://github.com/odoldotol/Either