repl

#!/usr/bin/lua
local env = require "scheme.env"
local readline, rl = pcall(require, "readline")

env = env.new_environment()
env:eval_file("core.scm")

-- Quick and dirty way to find out if the chunk has balanced parentheses
local function is_balanced(str)
    local open = 0
    local close = 0

    local instr = false

    for i = 1, #str do
        if str:sub(i, i) == "\"" and str:sub(i - 1, i - 1) ~= "\\" then
            instr = not instr
        end

        if not instr then
            if str:sub(i, i) == "(" then
                open = open + 1
            elseif str:sub(i, i) == ")" then
                close = close + 1
            end
        end
    end

    return open == close
end

local running = 0
local evalbuf = ""
while true do
    local prompt

    if #evalbuf == 0 then
        prompt = ("(input):%d > "):format(env.parser.line)
    else
        prompt = ("        %d.. "):format(env.parser.line)
    end

    local line

    if readline then
        line = rl.readline(prompt)
    else
        io.write(prompt)
        line = io.read("*l")
    end

    if not line then
        break
    end

    if readline then
        rl.add_history(line)
    end

    evalbuf = evalbuf .. line

    if is_balanced(evalbuf) then
        local res = env:eval(evalbuf .. "\n")

        if res then
            env:define("$" .. tostring(running), res)
            env:define("_", res)

            print((">> $%s = %s\n  %s"):format(
                running, tostring(res), res.type))

            running = running + 1
        end

        evalbuf = ""
    end
end

print("^D - bye!")