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https://github.com/mmottl/pcre-ocaml
OCaml bindings to PCRE (Perl Compatibility Regular Expressions)
https://github.com/mmottl/pcre-ocaml
ocaml pattern-matching pcre string-matching
Last synced: about 1 month ago
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OCaml bindings to PCRE (Perl Compatibility Regular Expressions)
- Host: GitHub
- URL: https://github.com/mmottl/pcre-ocaml
- Owner: mmottl
- License: other
- Created: 2014-07-06T14:30:44.000Z (over 10 years ago)
- Default Branch: master
- Last Pushed: 2024-12-14T07:01:15.000Z (about 1 month ago)
- Last Synced: 2024-12-14T07:20:57.008Z (about 1 month ago)
- Topics: ocaml, pattern-matching, pcre, string-matching
- Language: OCaml
- Size: 1.08 MB
- Stars: 31
- Watchers: 5
- Forks: 8
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGES.md
- License: LICENSE.md
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README
# PCRE-OCaml - Perl Compatibility Regular Expressions for OCaml
This [OCaml](http://www.ocaml.org) library interfaces with the C library
[PCRE](http://www.pcre.org), providing Perl-compatible regular expressions
for string matching.
## Features
PCRE-OCaml offers:
- Pattern searching
- Subpattern extraction
- String splitting by patterns
- Pattern substitution
Reasons to choose PCRE-OCaml:
- The PCRE library by Philip Hazel is mature and stable, implementing nearly
all Perl regular expression features. High-level OCaml functions (split,
replace, etc.) are compatible with Perl functions, as much as OCaml allows.
Some developers find Perl-style regex syntax more intuitive and powerful
than the Emacs-style regex used in OCaml's `Str` module.
- PCRE-OCaml is reentrant and thread-safe, unlike the `Str` module. This
reentrancy offers convenience, eliminating concerns about library state.
- High-level replacement and substitution functions in OCaml are faster than
those in the `Str` module. When compiled to native code, they can even
outperform Perl's C-based functions.
- Returned data is unique, allowing safe destructive updates without side
effects.
- The library interface uses labels and default arguments for enhanced
programming comfort.
## Usage
Please run:
```sh
odig odoc pcre2
```
Or:
```sh
dune build @doc
```
Consult the [API](https://mmottl.github.io/pcre-ocaml/api/pcre) for details.
Functions support two flag types:
1. **Convenience flags**: Readable and concise, translated internally on each
call. Example:
```ocaml
let rex = Pcre.regexp ~flags:[`ANCHORED; `CASELESS] "some pattern" in
(* ... *)
```
These are easy to use but may incur overhead in loops. For performance
optimization, consider the next approach.
2. **Internal flags**: Predefined and translated from convenience flags for
optimal loop performance. Example:
```ocaml
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
```
Translating flags outside loops saves cycles. Avoid creating regex in
loops:
```ocaml
for i = 1 to 1000 do
let chunks = Pcre.split ~pat:"[ \t]+" "foo bar" in
(* ... *)
done
```
Instead, predefine the regex:
```ocaml
let rex = Pcre.regexp "[ \t]+" in
for i = 1 to 1000 do
let chunks = Pcre.split ~rex "foo bar" in
(* ... *)
done
```
Functions use optional arguments with intuitive defaults. For instance,
`Pcre.split` defaults to whitespace as the pattern. The `examples` directory
contains applications demonstrating PCRE-OCaml's functionality.
## Restartable (Partial) Pattern Matching
PCRE includes a DFA match function for restarting partial matches with new
input, exposed via `pcre_dfa_exec`. While not suitable for extracting
submatches or splitting strings, it's useful for streaming and search tasks.
Example of a partial match restarted:
```ocaml
utop # open Pcre;;
utop # let rex = regexp "12+3";;
val rex : regexp =
utop # let workspace = Array.make 40 0;;
val workspace : int array =
[| ... |]
utop # pcre_dfa_exec ~rex ~flags:[`PARTIAL] ~workspace "12222";;
Exception: Pcre.Error Partial.
utop # pcre_dfa_exec ~rex ~flags:[`PARTIAL; `DFA_RESTART] ~workspace "2222222";;
Exception: Pcre.Error Partial.
utop # pcre_dfa_exec ~rex ~flags:[`PARTIAL; `DFA_RESTART] ~workspace "2222222";;
Exception: Pcre.Error Partial.
utop # pcre_dfa_exec ~rex ~flags:[`PARTIAL; `DFA_RESTART] ~workspace "223xxxx";;
- : int array = [|0; 3; 0|]
```
Refer to the `pcre_dfa_exec` documentation and the `dfa_restart` example for
more information.
## Contact Information and Contributing
Submit bug reports, feature requests, and contributions via the
[GitHub issue tracker](https://github.com/mmottl/pcre-ocaml/issues).
For the latest information, visit: