Questions about separatedBy

[stefan stanciulescu]

Hi all,

I have been making progress understanding how to use parboiled2 to write a very simple parser for reading C/C++ files into a very simple custom AST.

My problem is in understanding how separatedBy / using a separator and EOI works.

The simplified code is in http://pastebin.com/nHTZRF8a

Example string:
#ifdef A
test
#endif

This is what I get:

Unexpected end of input, expected '\n' or '\r' (line 3, column 7): #endif

I do understand that it expects a sep, as I wrote in the grammar, but if I change the sep rule to be :

def sep = rule{ch(EOI) | "\n" | "\r\n" }

the program does not terminate.

Now, I can use instead 

 rule{ zeroOrMore(line).separatedBy(sep)

which will work fine, except that it adds an extra empty line in my result, e.g. Vector(YourChoice(defined(A),Vector(Textline(test), Textline()),None))

I simplified my example, and I would prefer to use this separatedBy but how do I get it to not add an extra line? I do not understand where does that come from...

What am I missing, what am I doing wrong? (Quite a beginner in parsing, though I am trying to learn and understand better).

Thanks in advance for your time!

[Mathias Doenitz]

Stefan,

the difference between

zeroOrMore(line ~ sep)

and

line.*(sep)

is that the former will always expect (and match) a separator after a line, even the very last line,
while the latter will never match a trailing separator.

So given `line sep line` the former will match only `line sep` while the latter matches `line sep line`.

Cheers,
Mathias

---
mat...@parboiled.org
http://www.parboiled.org

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[stefan stanciulescu]

Thanks Mathias. I made it work, though now I have a different problem (parsing cyrillic and chinese etc :-) )