--- lam.base --- base environment

local base = {}
local type = require "type"
local isNull = type.isNull

base.env = {
	["+"] =
		function (r)
			local r, a = r, 0
			while r.cdr do
				r, a = r.cdr, a + r.car
			end
			return a
		end,
	["-"] =
		function (r)
			if isNull(r) then return -1 end
			if isNull(r.cdr) then return (- r.car) end
			local r, a = r.cdr, r.car
			while r.cdr do
				r, a = r.cdr, a - r.car
			end
			return a
		end,
}

---
return base