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VbPeg

PEG parser generator for VB6

Description

VbPeg is a simple parser generator for VB6 that can be used to build interpreters, compilers and other tools that need to match and process complex input data.

VbPeg generates recursive-descent parsers from Parsing Expression Grammars (PEG) [Ford 2004] and is currently based on the original Ford syntax with some additions for 'semantic actions' as implemented by Ian Piumarta's peg/leg project.

VbPeg is self-hosted, meaning it can produce it's own parser in src\cParser.cls from the grammar in VbPeg.peg in root.

Sample usage

  • Generate a private VB6 class from PEG grammar in VbPeg.peg
    c:> VbPeg.exe VbPeg.peg -o src\cParser

Command-line

Usage: VbPeg.exe [options] <in_file.peg>

Options:
  -o OUTFILE      write result to OUTFILE [default: stdout]
  -tree           output parse tree
  -ir             output intermediate represetation
  -set NAME=VALUE set or modify grammar settings
  -q              in quiet operation outputs only errors
  -nologo         suppress startup banner
  -allrules       output all rules (don't skip unused)
  -trace          trace in_file.peg parsing as performed by %1.exe

If no -tree/-ir is used emits VB6 code. If no -o is used writes result to console.

vbpeg's People

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vbpeg's Issues

Parametrized Rules

  • Defined with binexpr(ByVal MinPrec As Long) = ...
  • Arguments has to be supplied from referencing site expr = binexpr(0)
  • Params are available in
    • Predicates in current rule &{ GetBinopPrec($$text) >= MinPrec }
    • Arguments to other param rules binop(ByVal MinPrec As Long) = ... | unexpr(MinPrec)

VBA7 support

Generate code with conditional x64 API declares.

Template Rules

  • Defined with ListOf<elem, delim> = elem (delim elem)*
  • Can be invoked with ListOf<ID, ','> or List<id:ID { .AddIdent($id) }, ','>
  • Invokations resolved after parse tree generation by inlining (with param replacement)
  • Hint: TOKEN<> can be used to force inline if usage TOKEN without <> supported
  • Can be overloaded on number of params e.g. ListOf@1 vs ListOf@2
  • Can be used to implement Error<msg> or Warning<msg>

Limiting Repetition

The syntax is {min,max}, where min is zero or a positive integer number indicating the minimum number of matches, and max is an integer equal to or greater than min indicating the maximum number of matches. If the comma is present but max is omitted, the maximum number of matches is infinite. So {0,1} is the same as ?, {0,} is the same as *, and {1,} is the same as +. Omitting both the comma and max tells the engine to repeat the token exactly min times.

  • Use expr*<n,m> instead of curly braces

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