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Language Conversion

by Steve_BZ (Hermit)
on Sep 09, 2009 at 14:59 UTC ( #794377=perlquestion: print w/ replies, xml ) Need Help??
Steve_BZ has asked for the wisdom of the Perl Monks concerning the following question:

I wrote a little macro (in Komodo) to convert some VBScript subroutines to Perl (see below). It missed a few things, but then executing the Perl in the debugger soon got it working and it was much quicker than converting by hand. I wondered if anyone else has written routine to translate between other languages. Specifically, I'm looking for something to take the pain out of converting a few subroutines into C or C++ for my current Perl project for security reasons.

Here it is:

// Macro recorded on Thu Aug 13 2009 22:13:22 GMT-0300 komodo.assertMacroVersion(2); if (komodo.view && komodo.view.scintilla) { komodo.view.scintilla.focu +s(); } Find_ReplaceAllInMacro(window, 1, '\'', '#', true, 0, 2, true, false); Find_ReplaceAllInMacro(window, 0, '\'', '#', true, 0, 2, true, false); Find_ReplaceAllInMacro(window, 0, 'If', 'if (', true, 0, 2, true, fals +e); Find_ReplaceAllInMacro(window, 0, 'then ', ') {', true, 0, 2, true, fa +lse); Find_ReplaceAllInMacro(window, 0, 'then', ') {', true, 0, 2, true, fal +se); Find_ReplaceAllInMacro(window, 0, 'End If', '}', true, 0, 2, true, fal +se); Find_ReplaceAllInMacro(window, 0, 'End if', '}', true, 0, 2, true, fal +se); Find_ReplaceAllInMacro(window, 0, 'End IF', '}', true, 0, 2, true, fal +se); Find_ReplaceAllInMacro(window, 0, 'Else', '} else {', true, 0, 2, true +, false); Find_ReplaceAllInMacro(window, 0, 'Function', 'sub', true, 0, 2, true, + false); Find_ReplaceAllInMacro(window, 0, 'Fn_', '__', true, 0, 2, true, false +); Find_ReplaceAllInMacro(window, 0, 'Loc_', '$loc_', true, 0, 2, true, f +alse); Find_ReplaceAllInMacro(window, 0, 'Len(', 'length(', true, 0, 2, true, + false); Find_ReplaceAllInMacro(window, 0, 'Mid(', 'substr(', true, 0, 2, true, + false); Find_ReplaceAllInMacro(window, 0, 'mid(', 'substr(', true, 0, 2, true, + false); Find_ReplaceAllInMacro(window, 0, 'Left(', 'substr(', true, 0, 2, true +, false); Find_ReplaceAllInMacro(window, 0, 'true', '1', true, 0, 2, true, false +); Find_ReplaceAllInMacro(window, 0, 'TRUE', '1', true, 0, 2, true, false +); Find_ReplaceAllInMacro(window, 0, 'false', '0', true, 0, 2, true, fals +e); Find_ReplaceAllInMacro(window, 0, 'FALSE', '0', true, 0, 2, true, fals +e); Find_ReplaceAllInMacro(window, 0, '<>', '!=', true, 0, 2, true, false) +; Find_ReplaceAllInMacro(window, 0, ' mod ', ' % ', true, 0, 2, true, fa +lse);

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Re: Language Conversion
by halfcountplus (Hermit) on Sep 09, 2009 at 15:41 UTC
    If you don't find anything, I would start by writing C/C++ functions to replace all the perl built-ins used. This is a very very complicated project IMO.

    Hashes, if not basically all variables, will have to be the product of some function, as will regex's. I do not think any kind of "find and replace" strategy will work very well in the end: you should investigate lexing and parsing if you are not already familiar with the topic. This might give you the general idea, read supplementary to something else:

    http://www.intergate.com/~halfcountplus/CBCP/parsing.html

    (there's some simple examples in C of how a language parser works, based on the "Dragon Book" stuff mentioned by almut; fascinating and fun -- good luck!)
      ...for further reading i.e. as the exercise for the interested reader, Steve_BZ could do worse than get a copy of the O'Reilly lex & yacc nutshell reference - IMO, most enlightening.

      A user level that continues to overstate my experience :-))

        ...for even further reading, the next step would be the classical Dragon book on compiler design...

        Essentially, a compiler translates from one language into another — typically from a higher level language to a lower one, but there's no reason (in theory) it couldn't convert from Perl to C++ source. It's just that compilers are usually non-trivial to write, so no one may have done it yet...

        In this particular case (as parsing Perl is a particularly non-trivial task), it would probably be a good idea to reuse existing code (such as the regular source of the Perl interpreter, or PPI) for the side of parsing and constructing a syntax tree.  You'd "just" :) have to add code generation for the target language from the syntax tree, paying particular attention on how to realize the highly dynamic facilities which Perl provides in a more "static" language like C/C++.

Re: Language Conversion
by ikegami (Pope) on Sep 09, 2009 at 16:38 UTC

    Specifically, I'm looking for something to take the pain out of converting a few subroutines into C or C++ for my current Perl project for security reasons.

    "For security reasons"?

    I don't understand that, especially since every single piece of Perl code is implemented in C already. The only thing that's not in C is the order in which the C code is to be executed.

      s/For security reasons/to obfuscate and placate/g


      -Waswas
        No, just interfaces to other systems.

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