moy-fp/src/Function/curry.js

A functional programming library.

import __ from './__'

const _arity = (n, fn) => {
  /* eslint-disable no-unused-vars */
  switch(n){
    case 0:
      return function(){
        return fn.apply(null, arguments);
      };
    case 1:
      return function(a0){
        return fn.apply(null, arguments);
      };
    case 2:
      return function(a0, a1){
        return fn.apply(null, arguments);
      };
    case 3:
      return function(a0, a1, a2){
        return fn.apply(null, arguments);
      };
    case 4:
      return function(a0, a1, a2, a3){
        return fn.apply(null, arguments);
      };
    case 5:
      return function(a0, a1, a2, a3, a4){
        return fn.apply(null, arguments);
      };
    case 6:
      return function(a0, a1, a2, a3, a4, a5){
        return fn.apply(null, arguments);
      };
    case 7:
      return function(a0, a1, a2, a3, a4, a5, a6){
        return fn.apply(null, arguments);
      };
    case 8:
      return function(a0, a1, a2, a3, a4, a5, a6, a7){
        return fn.apply(null, arguments);
      };
    case 9:
      return function(a0, a1, a2, a3, a4, a5, a6, a7, a8){
        return fn.apply(null, arguments);
      };
    case 10:
      return function(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9){
        return fn.apply(null, arguments);
      };
    default:
      return function(...args){
        return fn.apply(null, arguments)
      }
  }
}

const _curry = (length, received, fn) => (...args) => {
  const combined = [],
        receivedLength = received.length,
        argsLength = args.length

  let left = length,
      receivedIndex = 0,
      argsIndex = 0,
      has__ = false,
      combinedOne
      
  while(receivedIndex < receivedLength ||
    argsIndex < argsLength){
    if(receivedIndex < receivedLength &&
      (received[receivedIndex] !== __ || argsIndex >= argsLength)
    ){
      combinedOne = received[receivedIndex]
    }else{
      combinedOne = args[argsIndex ++]
    }

    if(combinedOne !== __){
      left --
    }else{
      if(combined.length <= length){
        has__ = true
      }
    }

    combined.push(combinedOne)

    receivedIndex ++
  }

  return left <= 0 && !has__ ? fn.apply(null, combined) : _arity(left, _curry(length, combined, fn))
}

/**
 * ((a, b, c, ..., m) -> n) -> ((a, b, c, ..., m) -> n)
 */
const curry = fn => {
  const length = fn.length
  return _arity(length, _curry(length, [], fn))
}

export default curry