# y-combinator

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

All credits go to Haskell Curry.

Installation | Annotated source | Example | License

## 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
```