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Visual Basic 6.0 Grammar
Version 1.3, Sept 2010
J.R. Cordy, Queen's University, April 2006
Reference: http://www.int.gu.edu.au/courses/3008int/m03/FYI/Command_Syntax.htm
Thanks to the HCI teaching team at Griffith University.
Example:
txl Examples/Module1.bas
This is an approximate grammar for Visual Basic 6.0, drawn from the reference
above, old MS web pages and updated to handle many undocumented features
by experience with parsing a number of open and closed source applications.
This is a work in progress.
Known limitations and bugs:
1. This grammar processes VB is line-based but otherwise free-format in order to
be convenient for transformation. However it is not quite true that VB
is free-format, for example:
.picEdit.PaintPicture .picHidden1.Picture, 0, 0, , , Val(stCmd4), Val(stCmd5)
which this grammar will mistake for:
.picEdit.PaintPicture.picHidden1.Picture , 0, 0, , , Val (stCmd4), Val (stCmd5)
This case is rare, but short of parsing all spacing, I don't know how to solve it.
2. As with all real languages, many features and forms are implemented but not
properly documented. I've added these to the grammar as I've run across them,
but it's not always clear what the feature's syntax is in general so these
are approximations.
3. Comments [vbcomment] are handled and preserved, but not always well formatted
in output. This needs tuning in future.
4. Continuations are handled by treating the continuation symbol (_) and newline as
ignored comments. Thus they are not preserved in output, but rather removed
to yield (valid) long lines instead. If a real VB comment has a continuation,
this strategy fails.
5. There seems to be no definitive list of which words are keywords and which
reserved words, or whether there is any meaningful distinction in VB.
The keyword list below has been honed by experience.
6. Preprocessor statements only handle #if so far.
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Rev 24.9.10