I don't know if you've already used it, but Parsec includes some kind of a lexer through the <a href="http://hackage.haskell.org/packages/archive/parsec/3.1.0/doc/html/Text-Parsec-Language.html">Language</a> and <a href="http://hackage.haskell.org/packages/archive/parsec/3.1.0/doc/html/Text-Parsec-Token.html">Token</a> modules.<div>
You can start by having a look at the <a href="http://hackage.haskell.org/packages/archive/parsec/3.1.0/doc/html/Text-Parsec-Token.html#v:makeTokenParser">makeTokenParser</a> function.<div><br><div class="gmail_quote">On 31 October 2010 15:11, Nils Schweinsberg <span dir="ltr"><<a href="mailto:ml@n-sch.de">ml@n-sch.de</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Hi!<br>
<br>
I'm having a really hard time to write a correct parser for a small language I've developed. I have been trying to write a parser using parsec, but always get a lot of error messages like "unexpected "\n", expected ..., new-line or..." when trying to run the parser. Then I read about the happy parser and really liked the separation of lexing the text into tokens and parsing the actual logic behind those tokens. Since I couldn't get familiar with the lexer "alex" I gave up on the alex-happy-approach again and went back to parsec. But with that lexer->parser idea on my mind, my parser currently looks a lot like a lexer. So I came up with the idea of using a combination of parsec and happy, where I generate a list of tokens for my text via parsec and analyse it with happy.<br>
<br>
<br>
My questions would be:<br>
<br>
- Is this a valid approach?<br>
<br>
- What is your workflow on parsing complex data structures?<br>
<br>
- What about performance? Since my project is going to be an interpreted language parsing performance might be interesting aswell. I've read that happy is in general faster than parsec, but what if I combine both of them as I said above? I guess that parsing a simple list of tokens without any nested parser structures would be pretty fast?<br>
<br>
- Do you have any other ideas on how to improve my parser?<br>
<br>
- What are your general thoughts on happy vs. parsec?<br>
<br>
<br>
Thanks for any replies,<br>
<br>
Nils<br>
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</blockquote></div><br><br clear="all"><br>-- <br>Ozgur Akgun<br>
</div></div>