JS functional functions by github.com/targen

bacon-pancakes.js

function id(x) {
  return x;
}

function const_(x) {
  return function(_) {
    return x;
  };
}

function compose(f) {
  return function(g) {
    return function(x) {
      return f (g (x));
    };
  };
}

function flip(f) {
  return function(x) {
    return function (y) {
      return f (y) (x);
    };
  };
}

function join(f) {
  return function(x) {
    return f (x) (x);
  };
}

function liftM2(f) {
  return function (g) {
    return function(h) {
      return function(x) {
        return f (g (x)) (h (x));
      };
    };
  };
}

function add(x) {
  return function(y) {
    return x + y;
  };
}

function multiply(x) {
  return function(y) {
    return x * y;
  };
}

function div(x) {
  return function(y) {
    return x / y;
  };
}

function pair(a) {
  return function(b) {
    return [a, b];
  };
}

function fst(p) {
  return p[0];
}

function snd(p) {
  return p[1];
}

var split = function(x) {
  return pair (x) (x);
}

var first = function(f) {
  return function(p) {
    return pair (fst (p)) (f (snd (p)));
  };
}

var second = function(f) {
  return function(p) {
    return pair (f (fst (p))) (snd (p));
  };
}

var starstarstar = function(f) {
  return function(g) {
    return compose (first (f)) (second (g));
  };
}

var andandand = function(f) {
  return function(g) {
    return compose (starstarstar (f) (g)) (split);
  };
}

function cons(x) {
  return function(xs) {
    return [x].concat(xs);
  };
}

function empty(xs) {
  return xs.length == 0;
}

function head(xs) {
  return xs[0];
}

function tail(xs) {
  return xs.slice(1);
}

function foldr(f) {
  return function(z) {
    return function(xs) {
      return empty (xs) ? z : f (head (xs)) (foldr (f) (z) (tail (xs)));
    };
  };
}

function foldl(f) {
  return function(z) {
    return function(xs) {
      return empty (xs) ? z : foldl (f) (f (z) (head (xs))) (tail (xs));
    };
  };
}

function map(f) {
  return foldr (compose (cons) (f)) ([]);
}

function unfoldr(f) {
  return function(b) {
    var p = f (b);
    return empty (p) ? p : cons (head (p)) (unfoldr (f) (head (tail (p))));
  }
}

var enumFromTo = flip (function(y) {
    return unfoldr (function(b) { return b > y ? [] : [b, b + 1]; });
  }
);

function zip(xs) {
  return function(ys) {
    return empty (xs) ? [] : empty (ys) ? [] : cons (pair (head (xs)) (head (ys))) (zip (tail (xs)) (tail (ys)));
  };
}

var unzip = foldr (liftM2 (starstarstar) (compose (cons) (fst)) (compose (cons) (snd))) (pair ([]) ([]));