Gregory Woodhouse wrote:
On Jul 1, 2006, at 6:27 AM, David House wrote:
Hi all. I need a decent regex library and JRegex seems the perfect
choice: simple API, yet well-featured, as well as PCRE support. I want
to use it on a simple project which involves input files a little
larger than typical -- between 100KB and 500KB -- but still small
enough so as to not present a problem.
However, and I'm fairly sure JRegex is at fault here, my program
segfaults on an input of ~230KB. Has anyone used JRegex successfully
in this way before? If so, what tactics did you use?
Thanks in advance.
I have no idea how JRegex works, but regular expressions are normally implemented using finite automata, so the input size should be immaterial.
Gregory Woodhouse gregory.woodhouse@sbcglobal.net mailto:gregory.woodhouse@sbcglobal.net
"Judge a man by his questions not his answers." --Voltaire
It depends on the advanced features that you need. If you use sub-expression capturing then it often changes to a backtracking algorithm. This use of backtracking is true of the Text.Regex.Lazy.Full code, which creates a Parsec parser instead of a DFA. The CompatDFA module uses an automata (derived from the CTKLight code, http://www.cse.unsw.edu.au/~chak/haskell/ctk/ ), and as a bonus, the DFA itself is build in a Lazy fashion, so unexplored parts of the automata don't get built. I found creating a Parsec parser to do regex matching was possible, but a bit odd in places. Like CTK, it is more aimed at writing a Lexer/Parser than a simple matcher. At some point, the FastPackedString version of Text.Regex.Lazy should be changed to the new ByteString library. Perhaps there is even room to build in on (or present it as) a type class. -- Chris "I'm here tonight to present the award everyone's been waiting for: best movie. This award holds a special place in my heart because next year I'll be winning it for Snakes on a Plane." -- June 3, 2006, Samuel L. Jackson