[antlr-interest] Tweaking a source file.

[Loring Craymer]

Rodrigo used ANTLR 2 to create boo--it might be a good
idea to check out the grammar(s) he uses.  They should
be in the boo distribution.

ANTLR 3 is getting pretty robust, but is still in the
shakedown stage and as yet is poorly documented.  If
you have a tight deadline, it may be better to use
ANTLR 2 just because it is stable and well-documented.

--Loring

--- David Piepgrass <qwertie256 at gmail.com> wrote:

> I'm new to ANTLR and although I'm generally a quick
> study when it comes to
> languages, I could use a little help because I'm on
> a hard deadline.
> 
> I want to write a preprocessor for a simplified boo
> language (boo is a
> language that resembles Python). The preprocessor
> will process "unit"
> declarations for a unit checker. For example, you
> could write code like
> this:
> 
> def Energy(mass as double `kg`, speed as double
> `m/s`):
>     return 0.5*mass*Square(speed)
> 
> def Square(x as double):
>     return x*x
> 
> Then, the unit checker could automatically deduce
> that the return value of
> Energy() is measured in kg*m^2/s^2. It also has to
> spit out a new source
> file without the unit information:
> 
> def Energy(mass as double, speed as double):
>     return 0.5*mass*Square(speed)
> ....
> 
> So, the unit checker needs to:
> 
> 1. Strip out unit information such as `m/s`, to
> produce a new source file.
> 2. Create an AST, in order to do semantic analysis
> (i.e. unit checking.)
> 3. Process newlines and indentation as part of the
> syntax.
> 
> The first decision I need to make is, should I use
> ANTLR 2 or ANTLR 3? The
> readme for ANTLR 3 says "For example, to read in
> some input, tweak it, and
> write it back out preserving whitespace, is easy in
> v3." That sounds great
> because it is exactly what I need to accomplish. 
> But how can it be done?
> Does an example exist? For my application, I think
> an observer inserted
> between the lexer and parser can do the job--I just
> don't know the details.
> 
> The second big question is, what is the easiest way
> to make an AST, and is
> this task also easier in v3?
> 
> The third question is, how can one parse a language
> where indentation is
> syntactically significant?
> 
> -- 
> - David
> http://qwertie.net
> 


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