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DEPARTUREAdvent Calendar 2023

Day 7

色々な言語で簡単なREPLを実装する #lua

Last updated at Posted at 2023-12-06

続きです。

REPLとは

こちらの記事を参照してください。

Luaで実装する

main.lua

function main()
    local prompt = ""
    local event = ""

    while true do
        io.write("lua> ")
        prompt = io.read()

        if prompt == nil or prompt == "exit" then
            print("Bye!")
            break
        end

        -- eval(prompt)
        print(prompt)
    end
end

function eval(prompt)
    local func, err = load("return " .. prompt)
    if not func then
        print("Error: " .. err)
    else
        local ok, result = pcall(func)
        if ok then
            print(result)
        else
            print("Error: " .. result)
        end
    end
end

main()

実行する

$ lua main.lua
lua> 1 + 1
1 + 1
lua> foobar
foobar
lua> baz
baz
lua> exit
Bye!

ctrl-dのeofはprompt == nilで受けています。
evalはないっぽいので、少しごちゃごちゃ書いています。

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