comp.lua

README.md

comp.lua

comp.lua

local compresult

local COMP = {}

function COMP:__index(k)
	return COMP[k] or self:addop("index", k)
end

function COMP:__call(...)
	return self:addop("call", ...)
end

function COMP:__len()
	return self:addop("len")
end

function COMP.__lt(lhs, rhs)
	if getmetatable(lhs) == COMP then
		compresult = lhs:addop("lt", rhs)
	else
		compresult = rhs:addop("gt", lhs)
	end
end

function COMP:__concat(rhs)
	return self:addop("concat", rhs)
end

function COMP:addop(type, ...)
	self.ops[#self.ops + 1] = { type = type, params = {...} }
	return self
end

function COMP:func()
	local ops = self.ops

	self.ops = {}

	return function(value)
		local lastvalue

		for _, op in ipairs(ops) do
			if op.type == "index" then
				lastvalue = value
				value = value[op.params[1]]
			elseif op.type == "call" then
				local params = {}
				for i, p in ipairs(op.params) do params[i] = p end
				if params[1] == self then params[1] = lastvalue end
				value = value(table.unpack(params))
			elseif op.type == "len" then
				value = #value
			elseif op.type == "lt" then
				value = value < op.params[1]
			elseif op.type == "gt" then
				value = value > op.params[1]
			elseif op.type == "concat" then
				value = value .. op.params[1]
			end
		end

		return value
	end
end

debug.setmetatable(_G, {
	__index = function(_, k)
		if k:sub(1, 1) == "_" then
			local oldval = _G[k:sub(2)]

			_G[k:sub(2)] = setmetatable({ ops = {} }, COMP)

			return setmetatable({}, {
				__bor = function(_, rhs)
					local f = (compresult or rhs):func()
					compresult = nil
					_G[k:sub(2)] = oldval
					return f
				end
			})
		end
	end
})

comp_fp.lua

dofile("comp.lua")

local FUNC = {}
FUNC.__index = FUNC

function FUNC:filter(f)
	local out = {}
	for _, v in ipairs(self) do
		if f(v) then
			out[#out + 1] = v
		end
	end
	return setmetatable(out, FUNC)
end

function FUNC:map(f)
	local out = {}
	for i, v in ipairs(self) do
		out[i] = f(v)
	end
	return setmetatable(out, FUNC)
end

function FUNC:foreach(f)
	for _, v in ipairs(self) do
		f(v)
	end
end

function f(tab)
	return setmetatable(tab, FUNC)
end

-- EXAMPLE

f{ { foo = "bar" }, { foo = "as" }, { foo = "baz" }, { foo = "qux" }, { foo = "cr" } }
	:filter(_x | (#x.foo > 2))
	:map(_x | x.foo:sub(1, 1))
	:foreach(print)

comp_hello.lua

dofile("comp.lua")

local transform = _x | x:upper() .. "!"

print(transform("hello world"))