Non-greedy match

[Clint M. Frederickson]

Maybe I'm just missing something here, but I don't see a way to do a non-greedy match. For example, I am trying to match:

"if(condition) {"
but I am running into cases where the code actually looks like

"if(condition) return 0; <other code> {"

I want a minimal match here.

Thanks in advance for your response and for all your hard work on pyparsing!

[Paul McGuire]

If you are parsing a language such as C, you'll need to handle the case where the if statement is just a single statement, not enclosed in {}'s, as shown in your message.  In this case, it looks like the '{' that you are picking up has nothing to do with the if(condition) part.

I'm guessing you have something like (this is about 2% of what a complete C grammar would look like):

stmt = Forward()
if_stmt = Keyword('if') + LPAREN + expression + RPAREN + stmt + Optional( Keyword('else') + stmt )
for_stmt = Keyword('for') + ...
while_stmt = Keyword('while') + ...
assignment = varName + '=' + expression + SEMI
stmt << if_stmt | for_stmt | while_stmt | assignment | ( '{' + ZeroOrMore(stmt) + '}'

But to really answer your question, I'll need to see a bit more of your grammar, and the original BNF if it is not a common language like C/C++/Java/C#.

If in fact you *are* doing a language parser for one of these languages, I'll caution you that it will be a significant project.  The Verilog parser took me about 8-10 weeks, and I had a very clear BNF to work from, and I was already familiar with pyparsing before I started.

In any event, best of luck to you, write back if you need more help, and thanks for using pyparsing!

-- Paul