[antlr-interest] code translation

[James Abley]

2009/6/24 Benoit Fouletier <benblo+ANTLR at gmail.com>:
> Hi!
> Newbie to ANTLR here, hello all =).
> I'm trying to make a translator from Unity's JavaScript (sometimes called
> UnityScript) to C#. This particular JS implementation is made to compile to
> IL and run on Mono. It's actually based on Boo, the grammar was written
> by Rodrigo B. de Oliveira with ANTLR (don't know which version).
> So the 2 languages are very similar, they don't differ in principle, only in
> syntax. I've already achieved a lot with regular expressions but that just
> doesn't seem like the right tool for the job.
> 90% of the differences are in variable & function declaration, the core is
> the same.
> Basically, I need to translate this:
>
> function MyFunction(i : int, b : boolean) : String
> {
>     return i + " " + b;
> }
>
> to this:
>
> private string MyFunction(int i, boolean b)
> {
>     return i + " " + b;
> }
>
> I have access to the compiled lexer & parser (but not the original grammar).
> I've tried to go through the token stream and manually rearrange the
> declarations (which works but again, doesn't feel like the best way to do
> it).
> The thing is, I want to retain comments & formatting during translation, but
> the lexer doesn't give me the hidden tokens* (and anyway my little fiddlings
> would probably explode!).
> Also, I don't need a complete compiler: all the code I want to translate
> already compiles so I know it's valid.
>
> It seems to me like my needs are fairly simple (!), but I don't know what
> approach to take. If I were to rewrite the grammar (or just modify the
> ECMAScript grammar found here), are there ways to define translate rules, in
> the fashion of regex replacement? Or should I be able to get away with using
> the compiled lexer I have?
>
> Sorry my post is so long, I hope I've made the context clear. Cheers =),
>
>         Ben
>
> * I've read the token streams article in the v2 docs (it's not in the v3
> docs, is it still valid?), which is very informative... unfortunately when I
> setTokenCreator to a hidden stream, I don't get anything more.
> Here's my loop:
> UnityScriptLexer lexer = new UnityScriptLexer(file);
> lexer.setTokenCreator(new
> antlr.CommonHiddenStreamToken.CommonHiddenStreamTokenCreator());
>
> antlr.IHiddenStreamToken token;
> while ((token = (antlr.IHiddenStreamToken)lexer.nextToken()).Type != EOF)
> {
>     if (token.getHiddenBefore() != null)
>         LogToken(token.getHiddenBefore());   // this never happens
>
>     LogToken(token);
>
>     if (token.getHiddenAfter() != null)
>         LogToken(token.getHiddenAfter());    // this never happens
> }
> LogToken() just outputs to the console.
>
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http://www.antlr.org/wiki/display/ST/Language+Translation+Using+ANTLR+and+StringTemplate

That seems to be ANTLR 2. but relevant. You would need a grammar
though, rather than just the compiled lexer and parser.

The new book is supposed to contain information around this sort of
request. Ter might be able to tell more about that.

http://www.pragprog.com/titles/tpdsl/language-design-patterns

Cheers,

James