modlib/func.lua

-- Localize globals
local error, coroutine, modlib, unpack, select, setmetatable
	= error, coroutine, modlib, unpack, select, setmetatable

-- Set environment
local _ENV = {}
setfenv(1, _ENV)

no_op = function() end

function curry(func, ...)
	local args = { ... }
	return function(...) return func(unpack(args), ...) end
end

function curry_tail(func, ...)
	local args = { ... }
	return function(...) return func(unpack(modlib.table.concat({...}, args))) end
end

function curry_full(func, ...)
	local args = { ... }
	return function() return func(unpack(args)) end
end

function args(...)
	local args = { ... }
	return function(func) return func(unpack(args)) end
end

function value(val) return function() return val end end

function values(...)
	local args = { ... }
	return function() return unpack(args) end
end

function memoize(func)
	return setmetatable({}, {
		__index = function(self, key)
			local value = func(key)
			self[key] = value
			return value
		end,
		__call = function(self, arg)
			return self[arg]
		end,
		__mode = "k"
	})
end

-- Equivalent to `for x, y, z in iterator, state, ... do callback(x, y, z) end`
function iterate(callback, iterator, state, ...)
	local function loop(...)
		if ... == nil then return end
		callback(...)
		return loop(iterator(state, ...))
	end
	return loop(iterator(state, ...))
end

function for_generator(caller, ...)
	local co = coroutine.create(function(...)
		return caller(function(...)
			return coroutine.yield(...)
		end, ...)
	end)
	local args = {...}
	return function()
		if coroutine.status(co) == "dead" then
			return
		end
		local function _iterate(status, ...)
			if not status then
				error((...))
			end
			return ...
		end
		return _iterate(coroutine.resume(co, unpack(args)))
	end
end

-- Does not use select magic, stops at the first nil value
function aggregate(binary_func, total, ...)
	if total == nil then return end
	local function _aggregate(value, ...)
		if value == nil then return end
		total = binary_func(total, value)
		return _aggregate(...)
	end
	_aggregate(...)
	return total
end

function override_chain(func, override)
	return function(...)
		func(...)
		return override(...)
	end
end

--+ Calls func using the provided arguments, deepcopies all arguments
function call_by_value(func, ...)
	return func(unpack(modlib.table.deepcopy{...}, 1, select("#", ...)))
end

-- Functional wrappers for Lua's builtin metatable operators (arithmetic, concatenation, length, comparison, indexing, call)

function add(a, b) return a + b end

function mul(a, b) return a * b end

function div(a, b) return a / b end

function mod(a, b) return a % b end

function pow(a, b) return a ^ b end

function unm(a) return -a end

function concat(a, b) return a .. b end

function len(a) return #a end

function eq(a, b) return a == b end

function lt(a, b) return a < b end

function le(a, b) return a <= b end

function index(object, key) return object[key] end

function newindex(object, key, value) object[key] = value end

function call(object, ...) object(...) end

-- Functional wrappers for logical operators, suffixed with _ for syntactical convenience

function not_(a) return not a end
_ENV["not"] = not_

function and_(a, b) return a and b end
_ENV["and"] = and_

function or_(a, b) return a or b end
_ENV["or"] = or_

-- Export environment
return _ENV