--- lam.environment

local util = require "util"
local types = require("types")

if not table.unpack then table.unpack = unpack end

local global = {
	-- constants
	["#t"] = true,
	["#f"] = false,
}

--- Types ---

for name, func in pairs(types) do
	if name == "lamtype" then
		global.type = func
	else
		global[name] = func
	end
end

--- Basic functions ---

global.begin = function(...)
	local xs = {...}
	return xs[#xs]
end

global.car = util.car
global.cdr = util.cdr

global.list = function(...) return {...} end

--- Higher-order functions ---

global.apply = function(fn, ...)
	local args = {...}
	local last = args[#args]
	assert(types.luatype(last) == "table", "Bad apply")
	table.remove(args)
	for _, v in ipairs(last) do
		table.insert(args, v)
	end
	return fn(table.unpack(args))
end

global.map = function(fn, list)
	return util.map(fn, list)
end

--- Math ---
-- NOTE: we do not have the full numeric tower yet!

for name, func in pairs(math) do
	global[name] = func
end

global["+"] = function (...)
	return util.reduce({...}, 0, function (a, b) return a + b end)
end

global["-"] = function (...)
	local args = {...}
	if #args == 0 then
		error("Too few arguments: need at least 1")
	elseif #args == 1 then
		return (-args[1])
	else
		local result = args[1]
		for v = 2, #args do
			result = result - args[v]
		end
		return result
	end
end

global["*"] = function (...)
	local result = 1
	for _, v in ipairs({...}) do
		if v == 0 then return 0 end
		result = result * v
	end
	return result
end

global["/"] = function (...)
	local args = {...}
	if #args == 0 then
		error("Too few arguments: need at least 1")
	elseif #args == 1 then
		if args[1] == 0 then error("Division by zero") end
		return (1/args[1])
	else
		local result = args[1]
		for v = 2, #args do
			if args[v] == 0 then error("Division by zero") end
			result = result / args[v]
		end
		return result
	end
end

global["="] = function (...)
	for _, v in ipairs({...}) do
		if not a == b then return false end
	end
	return true
end

global["<"] = function (...)
	for _, v in ipairs({...}) do
		if not a < b then return false end
	end
	return true
end

global["<="] = function (...)
	for _, v in ipairs({...}) do
		if not a <= b then return false end
	end
	return true
end

global[">"] = function (...)
	for _, v in ipairs({...}) do
		if not a > b then return false end
	end
	return true
end

global[">="] = function (...)
	for _, v in ipairs({...}) do
		if not a >= b then return false end
	end
	return true
end

---
return global