PCRE-OCaml - Perl Compatibility Regular Expressions for OCaml

This OCaml-library interfaces the C-library PCRE (Perl-compatibility Regular Expressions). It can be used for string matching with “PERL”-style regular expressions.

Features

PCRE-OCaml offers the following functionality for operating on strings:

Other reasons to use PCRE-OCaml:

Usage

Please consult the API for details.

A general concept the user may need to understand is that most functions allow for two different kinds of flags:

  1. “Convenience”-flags that make for readable and concise code, but which need to be translated to an internal representation on each call. Example:

    let rex = Pcre.regexp ~flags:[`ANCHORED; `CASELESS] "some pattern" in
    (* ... *)
    

    This makes it easy to pass flags on the fly. They will be translated to the internal format automatically. However, if this happens to be in a loop, this translation will occur on each iteration. If you really need to save as much performance as possible, you should use the next approach.

  2. “Internal” flags that need to be defined and translated from “convenience”-flags before function calls, but which allow for optimum performance in loops. Example:

    let iflags = Pcre.cflags [`ANCHORED; `CASELESS] in
    for i = 1 to 1000 do
      let rex = Pcre.regexp ~iflags "some pattern constructed at runtime" in
      (* ... *)
    done
    

    Factoring out the translation of flags for regular expressions may save some cycles, but don’t expect too much. You can save more CPU time when lifting the creation of regular expressions out of loops. Example for what not to do:

     for i = 1 to 1000 do
       let chunks = Pcre.split ~pat:"[ \t]+" "foo bar" in
       (* ... *)
     done
    

    Better:

     let rex = Pcre.regexp "[ \t]+" in
     for i = 1 to 1000 do
       let chunks = Pcre.split ~rex "foo bar" in
       (* ... *)
     done
    

The provided functions use optional arguments with intuitive defaults. For example, the Pcre.split-function will assume whitespace as pattern. The examples-directory contains a few example applications demonstrating the functionality of PCRE-OCaml.

Contact Information and Contributing

Please submit bugs reports, feature requests, contributions and similar to the GitHub issue tracker.

Up-to-date information is available at: https://mmottl.github.io/pcre-ocaml