curry.js

(function() {

    var curry = function(f) {
        var c = function(l, args) {
            return function(a) {
                switch(l) {
                case 1:
                    args.push(a)
                case 0:
                    return f.apply(this, args)
                default:
                    args.push(a)
                    return c(l-1, args)
                }
            }
        }
        return c(f.length, [])
    }

    test("curry 0 argument", function() {
        var curried = curry(function() {
            return 10
        })
        equal(curried(), 10)
    })

    test("curry 1 argument", function() {
        var curried = curry(function(a) {
            return a
        })
        equal(curried(1), 1)
    })

    test("curry 2 arguments", function() {
        var curried = curry(function(a, b) {
            return a + b
        })
        //equal(curried(1), function(b) {})
        equal(curried(1)(2), 3)
        equal(curried(1)(2), 3) //ensure that curried has no state.
    })

    test("curry 3 arguments", function() {
        var curried = curry(function(a, b, c) {
            return a * b * c
        })
        equal(curried(1)(2)(3), 6)
    })

    var flip = function(curried) {
        return function(a) {
            return function(b) {
                return curried(b)(a)
            }
        }
    }

    /* this will causes error.
    test("flip 0 arguments", function() {
        equal(
            flip(curry(function() {
                return 10
            }))(),
            10
        )
    })
    */

    /* this will causes error.
    test("flip 1 arguments", function() {
        equal(
            flip(curry(function(a) {
                return a
            }))(3),
            3
        )
    })
    */

    test("flip 2 arguments", function() {
        equal(
            flip(curry(function(a, b) {
                return a - b
            }))(3)(5),
            5 - 3
        )
    })

    test("flip 3 arguments", function() {
        equal(
            flip(curry(function(a, b, c) {
                return a - b * c
            }))(3)(5)(10),
            5 - 3 * 10
        )
    })

})()