fun.js

not_implemented = function () {
    throw "Implement me!"
}

map_list     = not_implemented
map_nullable = not_implemented
map_function = not_implemented

assert_equal = function (x, y) {
    console.log(JSON.stringify(x) == JSON.stringify(y)? "Yes" : "NO")
}

var inc = function (x) { return x + 1 }

assert_equal(map_list([1,2,3], inc), [2,3,4])

assert_equal(map_nullable(5, inc), 6)

assert_equal(map_nullable(null, inc), null)

assert_equal(map_function(JSON.stringify, inc)(1), "2")

//---

pure_list     = not_implemented
pure_nullable = not_implemented
pure_function = not_implemented

assert_equal(pure_list(5), [5])
assert_equal(pure_nullable(5), 5)
assert_equal(pure_function(5)("whatever"), 5)

//---

// bind is flat_map

bind_list = not_implemented

bind_nullable = not_implemented

bind_function = not_implemented

non_null_inv = function (x) {
    if (x == 0)
        return []
    else
        return [x, 1/x]
}

non_null_inv1 = function (x) {
    if (x == 0)
        return null
    else
        return 1/x
}

assert_equal(bind_list([-2,0,2], non_null_inv), [-2, -0.5, 2, 0.5])

assert_equal(bind_nullable(null, non_null_inv1), null)
assert_equal(bind_nullable(0,    non_null_inv1), null)
assert_equal(bind_nullable(2,    non_null_inv1), 0.5)

assert_equal(
    bind_function(
        function (env) { return 1 + env["count"] },
        function (newcount) {
            return function (env) {
                return "count was " + env["count"] + ", became " + newcount
            }
        }
    )({count: 5}),
    "count was 5, became 6"
)