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local spy = require "luassert.spy"
local match = require "luassert.match"
local _ = require "mason-core.functional"
describe("functional: function", function()
it("curries functions", function()
local function sum(...)
local res = 0
for i = 1, select("#", ...) do
res = res + select(i, ...)
end
return res
end
local arity0 = _.curryN(sum, 0)
local arity1 = _.curryN(sum, 1)
local arity2 = _.curryN(sum, 2)
local arity3 = _.curryN(sum, 3)
assert.equals(0, arity0(42))
assert.equals(42, arity1(42))
assert.equals(3, arity2(1)(2))
assert.equals(3, arity2(1, 2))
assert.equals(6, arity3(1)(2)(3))
assert.equals(6, arity3(1, 2, 3))
-- should discard superfluous args
assert.equals(0, arity1(0, 10, 20, 30))
end)
it("coalesces first non-nil value", function()
assert.equals("Hello World!", _.coalesce(nil, nil, "Hello World!", ""))
end)
it("should compose functions", function()
local function add(x)
return function(y)
return y + x
end
end
local function subtract(x)
return function(y)
return y - x
end
end
local function multiply(x)
return function(y)
return y * x
end
end
local big_maths = _.compose(add(1), subtract(3), multiply(5))
assert.equals(23, big_maths(5))
end)
it("should not allow composing no functions", function()
local e = assert.has_error(function()
_.compose()
end)
assert.equals("compose requires at least one function", e)
end)
it("should partially apply functions", function()
local funcy = spy.new()
local partially_funcy = _.partial(funcy, "a", "b", "c")
partially_funcy("d", "e", "f")
assert.spy(funcy).was_called_with("a", "b", "c", "d", "e", "f")
end)
it("should partially apply functions with nil arguments", function()
local funcy = spy.new()
local partially_funcy = _.partial(funcy, "a", nil, "c")
partially_funcy("d", nil, "f")
assert.spy(funcy).was_called_with("a", nil, "c", "d", nil, "f")
end)
it("memoizes functions with default cache mechanism", function()
local expensive_function = spy.new(function(s)
return s
end)
local memoized_fn = _.memoize(expensive_function)
assert.equals("key", memoized_fn "key")
assert.equals("key", memoized_fn "key")
assert.equals("new_key", memoized_fn "new_key")
assert.spy(expensive_function).was_called(2)
end)
it("memoizes function with custom cache mechanism", function()
local expensive_function = spy.new(function(arg1, arg2)
return arg1 .. arg2
end)
local memoized_fn = _.memoize(expensive_function, function(arg1, arg2)
return arg1 .. arg2
end)
assert.equals("key1key2", memoized_fn("key1", "key2"))
assert.equals("key1key2", memoized_fn("key1", "key2"))
assert.equals("key1key3", memoized_fn("key1", "key3"))
assert.spy(expensive_function).was_called(2)
end)
it("should evaluate functions lazily", function()
local impl = spy.new(function()
return {}, {}
end)
local lazy_fn = _.lazy(impl)
assert.spy(impl).was_called(0)
local a, b = lazy_fn()
assert.spy(impl).was_called(1)
assert.is_true(match.is_table()(a))
assert.is_true(match.is_table()(b))
local new_a, new_b = lazy_fn()
assert.spy(impl).was_called(1)
assert.is_true(match.is_ref(a)(new_a))
assert.is_true(match.is_ref(b)(new_b))
end)
it("should support nil return values in lazy functions", function()
local lazy_fn = _.lazy(function()
return nil, 2
end)
local a, b = lazy_fn()
assert.is_nil(a)
assert.equals(2, b)
end)
it("should provide identity value", function()
local obj = {}
assert.equals(2, _.identity(2))
assert.equals(obj, _.identity(obj))
end)
it("should always return bound value", function()
local obj = {}
assert.equals(2, _.always(2)())
assert.equals(obj, _.always(obj)())
end)
it("true is true and false is false", function()
assert.is_true(_.T())
assert.is_false(_.F())
end)
end)
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