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y-combinator

is one of the fixed-point combinators in untyped lambda calculus

y-combinator

is one of the fixed-point combinators in untyped lambda calculus

All credits go to Haskell Curry.

Installation | Annotated source | Example | License

KLP Build Status

Installation

npm install y-combinator

Annotated source

I have no idea what is the Y combinator operator (maybe one day I will :P), I have just stolen the code from a guy called Douglas Crockford a.k.a Walker Texas JS.

Here it is the code, it is a function that consumes a function and returns a function, that consumes a function that returns a function ...

function Y(le) {
  return (function (f) {
    return f(f)
  }(function (f) {
    return le(function (x) {
      return f(f)(x)
    })
  }))
}

... ok, now export the Y function

module.exports = Y

Example

Q. What can I do with the Y Combinator?

A. Mmh, for example you can use it to get a factorial function, the following code works!

var Y = require('y-cominator')
 
var factorial = Y(fac => n => n <= 2 ? n : n * fac(n - 1))
 
console.log(factorial(5)) // 120

License

MIT