# pcre-heavy [](https://hackage.haskell.org/package/pcre-heavy) [](https://travis-ci.org/myfreeweb/pcre-heavy) [](http://unlicense.org)
*Finally!* A Haskell regular expressions library that does not suck.
- based on [pcre-light], none of that regex-base complicated pluggable-backend stuff
- takes and returns [ConvertibleStrings] everywhere, use ANY STRING TYPE (String, ByteString, Lazy ByteString, Text, Lazy Text) -- but you need a bit more type annotations (or [ClassyPrelude]'s `asText`, `asString`, etc.) if you use `OverloadedStrings` which you probably can't live without
- a QuasiQuoter for regexps that does compile time checking (BTW, [vim2hs] has correct syntax highlighting for that!)
- **SEARCHES FOR MULTIPLE MATCHES! DOES REPLACEMENT!**
[pcre-light]: https://hackage.haskell.org/package/pcre-light
[ConvertibleStrings]: https://hackage.haskell.org/package/string-conversions
[ClassyPrelude]: https://hackage.haskell.org/package/classy-prelude
[vim2hs]: https://github.com/dag/vim2hs#quasi-quoting
## Usage
```haskell
{-# LANGUAGE QuasiQuotes, FlexibleContexts #-}
import Text.Regex.PCRE.Heavy
```
### Checking
```haskell
>>> "https://unrelenting.technology" =~ [re|^http.*|]
True
```
For `UnicodeSyntax` fans, it's also available as ≈ (U+2248 ALMOST EQUAL TO):
```haskell
>>> "https://unrelenting.technology" ≈ [re|^http.*|]
True
```
### Matching (Searching)
(You can use any string type, not just String!)
`scan` returns all matches as pairs like `(fullmatch, [group, group...])`.
```haskell
>>> scan [re|\s*entry (\d+) (\w+)\s*&?|] " entry 1 hello &entry 2 hi" :: [(String, [String])]
[
(" entry 1 hello &", ["1", "hello"])
, ("entry 2 hi", ["2", "hi"])
]
```
It is lazy!
If you only need the first match, use `head` (or, much better, `headMay` from [safe]) -- no extra work will be performed!
```haskell
>>> headMay $ scan [re|\s*entry (\d+) (\w+)\s*&?|] " entry 1 hello &entry 2 hi"
Just (" entry 1 hello &", ["1", "hello"])
```
[safe]: https://hackage.haskell.org/package/safe
### Replacement
`sub` replaces the first match, `gsub` replaces all matches.
```haskell
-- You can use a Stringable type as the replacement...
>>> gsub [re|\d+|] "!!!NUMBER!!!" "Copyright (c) 2015 The 000 Group"
"Copyright (c) !!!NUMBER!!! The !!!NUMBER!!! Group"
-- or a (Stringable a => [a] -> a) function -- that will get the groups...
>>> gsub [re|%(\d+)(\w+)|] (\(d:w:_) -> "{" ++ d ++ " of " ++ w ++ "}" :: String) "Hello, %20thing"
"Hello, {20 of thing}"
-- or a (Stringable a => a -> a) function -- that will get the full match...
>>> gsub [re|-\w+|] (\x -> "+" ++ (reverse $ drop 1 x) :: String) "hello -world"
"hello +dlrow"
-- or a (Stringable a => a -> [a] -> a) function.
-- That will get both the full match and the groups.
-- I have no idea why you would want to use that, but that's there :-)
```
### Splitting
`split`, well, splits.
```haskell
>>> split [re|%(begin|next|end)%|] "%begin%hello%next%world%end%"
["","hello","world",""]
```
### Options
You can pass `pcre-light` options by using the `somethingO` variants of functions (and `mkRegexQQ` for compile time options):
```haskell
>>> let myRe = mkRegexQQ [multiline, utf8, ungreedy]
>>> scanO [myRe|\s*entry (\d+) (\w+)\s*&?|] [exec_no_utf8_check] " entry 1 hello &entry 2 hi" :: [[String]]
>>> gsubO [myRe|\d+|] [exec_notempty] "!!!NUMBER!!!" "Copyright (c) 2015 The 000 Group"
```
`utf8` is passed by default in the `re` QuasiQuoter.
## Development
Use [stack] to build.
Use ghci to run tests quickly with `:test` (see the `.ghci` file).
```bash
$ stack build
$ stack test && rm tests.tix
$ stack ghci --ghc-options="-fno-hpc"
```
[stack]: https://github.com/commercialhaskell/stack
## Contributing
Please feel free to submit pull requests!
Bugfixes and simple non-breaking improvements will be accepted without any questions :-)
By participating in this project you agree to follow the [Contributor Code of Conduct](http://contributor-covenant.org/version/1/2/0/).
## License
This is free and unencumbered software released into the public domain.
For more information, please refer to the `UNLICENSE` file or [unlicense.org](http://unlicense.org).