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The Hoa\Regex library. 2017-01-13 16:10 UTC



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Hoa is a modular, extensible and structured set of PHP libraries.
Moreover, Hoa aims at being a bridge between industrial and research worlds.


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This library provides tools to analyze regular expressions and generate strings based on regular expressions (Perl Compatible Regular Expressions).

Learn more.


With Composer, to include this library into your dependencies, you need to require hoa/regex:

$ composer require hoa/regex '~1.0'

For more installation procedures, please read the Source page.


Before running the test suites, the development dependencies must be installed:

$ composer install

Then, to run all the test suites:

$ vendor/bin/hoa test:run

For more information, please read the contributor guide.

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 to lex, parse and produce an AST of the following regular expression: ab(c|d){2,4}e?. Thus:

// 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.

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:

$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.


The hack book of Hoa\Regex contains detailed information about how to use this library and how it works.

To generate the documentation locally, execute the following commands:

$ composer require --dev hoa/devtools
$ vendor/bin/hoa devtools:documentation --open

More documentation can be found on the project's website: hoa-project.net.

Getting help

There are mainly two ways to get help:


Do you want to contribute? Thanks! A detailed contributor guide explains everything you need to know.


Hoa is under the New BSD License (BSD-3-Clause). Please, see LICENSE for details.