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I would like to add scripting support to an applications and with plenty scripting languages available I am a bit overwhelmed.

At first I thought about Python but I guess Python is a little too big for my taste and the application (although I like it very much, it gets a lot of things right in my opinion while the syntax is clean and simple especially if you are not doing heavy OOP).

I am also very fond of Lisps. I like scheme and it is the perfect extension language - at least in some ways, but I would like to stay syntactically more conservative.

I remember having heard a lot of positive things about Lua and indeed Lua seems a good possibility. Unfortunately there is this one thing that really "turns me off": Its the local keyword for local binding. This is really ugly to my taste and I frankly do not quite grok why languages are still designed this way and in essence knowing about local. This is also a major drawback of JavaScript in my opinion and I feel like it all boils down to bad language design. My major concern is, that a user might just override a function from just within her/his function just by omitting local.

But then Lua gets a lot of things right, size, speed, and it is surprisingly scheme-esque. Yet I am really afraid that it is not suitable for non-programmers who have no sense of scope.

  • Any alternatives on the horizon?

  • Might hacking the Luacore to make local the default be an option?

    Lua sources appear to be quite decent and modular, so this would be an interesting project ;)

Joachim Sauer
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wirrbel
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2 Answers2

8

local is mandatory attribute of full lexical scoping:

local x = 0
function f(inc)
    x = x + inc -- if you auto-localize it, this is broken
end

On the other hand, we probably could remove local from the language, but add complementing outer (bound, upvalue, you name it):

x, y = 0, 0
function f(inc)
    outer x
    x = x + inc -- uses outer slot: "0 + inc"
    y = y + inc -- creates local (and raises "nil + number" error)
end

If you do not have either (including regular globals), your scoping is just useless.

Lua parser is written well, although I don't think it will be trivial fix.

2

I'd suggest TCL, its designed to be an embedded scripting language that can define DSLs for non-programmers.

The key thing with TCL, scheme or any solution here though is designing a DSL that the user can understand, with a good enough DSL the user should rarely need general programming constructs (which could be harder to comprehend)

WRT your comment TCL doesn't really have a grammar so I wonder if you are misunderstanding something about it? Or rather its grammar is about as complex as schemes.

jk.
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