Hardcore functional programming (exercise 1)

list functions.js

var _ = R;

/*****************************************
      C U R R Y I N G  E X A M P L E
******************************************/

// We've got a nice multiply function.
// It takes two arguments.

console.log( _.multiply(3, 4) );

// But it has been secretly curried already 
// so we can feed it fewer arguments and it 
// will return a new function.
//
// How about making a function to double a 
// value? Done.
var double = _.multiply(2);

console.log( double(13) );

/*****************************************
               Y O U R  T U R N
******************************************/

// _.split pulls a string apart around a
// given value
console.log( _.split('i', 'mississippi') );

// -- Challenge 1 ------------------------
// Make a function called "words" which 
// returns a list of words in a string.
// Use only the split function and
// currying.

console.log("Testing challenge 1...");

var words = _.split(' '); // change this
assertEqualArrays(
  ['one', 'two', 'three'],
  words('one two three')
);
console.log("passed");

// -- Challenge 2 ------------------------
// Create a function to triple every
// number in a list using only
// _.multiply and _.map.

console.log("Testing challenge 2...");

var tripleList = _.map(_.multiply(3))
assertEqualArrays([3,6,9], tripleList([1,2,3]));

console.log("passed");

// -- Challenge 3 ------------------------
// Create a function to find the largest
// number in a list. You can use the
// greater(a,b) function which returns the
// greater of its two inputs. You can do
// this with currying and one of the list
// functions _.map, _.filter, or _.reduce.

console.log("Testing challenge 3...");

var greater = function(a,b) {
  return a > b ? a : b;
};

var max = _.reduce(greater, _.map)
assertEqual(9, max([1,-3483,9,7,2]));
assertEqual(-1, max([-21,-3483,-2,-1]));

console.log("passed");


console.log("All tests pass.");
/******************************************
        B A C K G R O U N D  C O D E
*******************************************/

function assertEqualArrays(x,y) {
  if(x.length !== y.length) throw("expected "+x+" to equal "+y);
  for(var i in x) {
    if(x[i] !== y[i]) {
      throw("expected "+x+" to equal "+y);
    }
  }
}
function assertEqual(x,y){
  if(x !== y) throw("expected "+x+" to equal "+y);
}

OUTPUTS

console.log(max)
function (n){return r(t,u,n)}

console.log(_.reduce(greater))
function (t,e){
  switch(arguments.length){
    case 0:throw n();
    case 1:return function(n){
      return r(t,n)
    };
    default: return r(t,e)
  }
}

http://jsbin.com/romun