Curry method in JavaScript

gistfile1.js

if (typeof Function.prototype.curry === 'undefined') {
  Function.prototype.curry = function() {
    var func = this
      , a = Array.prototype.slice.call(arguments, 0)
    return function () {
      var a_len = a.length
        , length = arguments.length
      while (length--)
        a[a_len + length] = arguments[length]
      return func.apply(this, a)
    }
  }
}


// Example 01
function xy (x, y) { return x + y }
var x = xy.curry(7)
x(3)     // 10

// Example 02
var warn = alert.curry("Warning!")
warn()