---
Hoa is a modular, extensible and
structured set of PHP libraries.
Moreover, Hoa aims at being a bridge between industrial and research worlds.
# Hoa\Regex
[](https://webchat.freenode.net/?channels=#hoaproject)
[](https://gitter.im/hoaproject/central)
[](https://central.hoa-project.net/Documentation/Library/Regex)
[](https://waffle.io/hoaproject/regex)
This library provides tools to analyze regular expressions and generate strings
based on regular expressions ([Perl Compatible Regular
Expressions](http://pcre.org)).
[Learn more](https://central.hoa-project.net/Documentation/Library/Regex).
## Installation
With [Composer](https://getcomposer.org/), to include this library into
your dependencies, you need to
require [`hoa/regex`](https://packagist.org/packages/hoa/regex):
```sh
$ composer require hoa/regex '~1.0'
```
For more installation procedures, please read [the Source
page](https://hoa-project.net/Source.html).
## Testing
Before running the test suites, the development dependencies must be installed:
```sh
$ composer install
```
Then, to run all the test suites:
```sh
$ vendor/bin/hoa test:run
```
For more information, please read the [contributor
guide](https://hoa-project.net/Literature/Contributor/Guide.html).
## Quick usage
As a quick overview, we propose to see two examples. First, analyze a regular
expression, i.e. lex, parse and produce an AST. Second, generate strings based
on a regular expression by visiting its AST with an isotropic random approach.
### Analyze regular expressions
We need the [`Hoa\Compiler`
library](https://central.hoa-project.net/Resource/Library/Compiler) to lex, parse
and produce an AST of the following regular expression: `ab(c|d){2,4}e?`. Thus:
```php
// 1. Read the grammar.
$grammar = new Hoa\File\Read('hoa://Library/Regex/Grammar.pp');
// 2. Load the compiler.
$compiler = Hoa\Compiler\Llk\Llk::load($grammar);
// 3. Lex, parse and produce the AST.
$ast = $compiler->parse('ab(c|d){2,4}e?');
// 4. Dump the result.
$dump = new Hoa\Compiler\Visitor\Dump();
echo $dump->visit($ast);
/**
* Will output:
* > #expression
* > > #concatenation
* > > > token(literal, a)
* > > > token(literal, b)
* > > > #quantification
* > > > > #alternation
* > > > > > token(literal, c)
* > > > > > token(literal, d)
* > > > > token(n_to_m, {2,4})
* > > > #quantification
* > > > > token(literal, e)
* > > > > token(zero_or_one, ?)
*/
```
We read that the whole expression is composed of a single concatenation of two
tokens: `a` and `b`, followed by a quantification, followed by another
quantification. The first quantification is an alternation of (a choice betwen)
two tokens: `c` and `d`, between 2 to 4 times. The second quantification is the
`e` token that can appear zero or one time.
We can visit the tree with the help of the [`Hoa\Visitor`
library](https://central.hoa-project.net/Resource/Library/Visitor).
### Generate strings based on regular expressions
To generate strings based on the AST of a regular expressions, we will use the
`Hoa\Regex\Visitor\Isotropic` visitor:
```php
$generator = new Hoa\Regex\Visitor\Isotropic(new Hoa\Math\Sampler\Random());
echo $generator->visit($ast);
/**
* Could output:
* abdcde
*/
```
Strings are generated at random and match the given regular expression.
## Documentation
The
[hack book of `Hoa\Regex`](https://central.hoa-project.net/Documentation/Library/Regex)
contains detailed information about how to use this library and how it works.
To generate the documentation locally, execute the following commands:
```sh
$ composer require --dev hoa/devtools
$ vendor/bin/hoa devtools:documentation --open
```
More documentation can be found on the project's website:
[hoa-project.net](https://hoa-project.net/).
## Getting help
There are mainly two ways to get help:
* On the [`#hoaproject`](https://webchat.freenode.net/?channels=#hoaproject)
IRC channel,
* On the forum at [users.hoa-project.net](https://users.hoa-project.net).
## Contribution
Do you want to contribute? Thanks! A detailed [contributor
guide](https://hoa-project.net/Literature/Contributor/Guide.html) explains
everything you need to know.
## License
Hoa is under the New BSD License (BSD-3-Clause). Please, see
[`LICENSE`](https://hoa-project.net/LICENSE) for details.