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Merge pull request #3044 from WouterJ/document_expressionlanguage
[WIP] Add docs for ExpressionLanguage component
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‎components/expression_language/index.rst

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Expression Language
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===================
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.. toctree::
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:maxdepth: 2
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introduction
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syntax

‎components/expression_language/introduction.rst

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.. index::
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single: Expressions
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Single: Components; Expression Language
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The ExpressionLanguage Component
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=================================
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The ExpressionLanguage component provides an engine that can compile and
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evaluate expressions. An expression is a one-liner that returns a value
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(mostly, but not limited to, Booleans).
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.. versionadded:: 2.4
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The ExpressionLanguage component was new in Symfony 2.4.
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Installation
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------------
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You can install the component in 2 different ways:
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* Use the official Git repository (https://github.com/symfony/expression-language);
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* :doc:`Install it via Composer </components/using_components>` (``symfony/expression-language`` on `Packagist`_).
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Usage
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-----
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The ExpressionLanguage component can compile and evaluate expressions.
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Expressions are one-liners which most of the time return a boolean, you can
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compare them to the expression in an ``if`` statement. A simple example of an
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expression is ``1 + 2``. You can also use more complicated expressions, such
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as ``someArray[3].someMethod('bar')``.
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The component provides 2 ways to work with expressions:
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* **compile**: the expression is compiled to PHP, so it can be cached and
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evaluated;
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* **evaluation**: the expression is evaluated without being compiled to PHP.
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The main class of the component is
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:class:`Symfony\\Component\\ExpressionLanguage\\ExpressionLanguage`::
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use Symfony\Component\ExpressionLanguage\ExpressionLanguage;
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$language = new ExpressionLanguage();
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echo $language->evaluate('1 + 2'); // displays 3
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echo $language->compile('1 + 2'); // displays (1 + 2)
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Expression Syntax
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-----------------
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See ":doc:`/components/expression_language/syntax`" to learn the syntax of the
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ExpressionLanguage component.
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.. _Packagist: https://packagist.org/packages/symfony/expression-language

‎components/expression_language/syntax.rst

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.. index::
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single: Syntax; ExpressionLanguage
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The Expression Syntax
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=====================
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The ExpressionLanguage component uses a specific syntax which is based on the
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expression syntax of Twig. In this document, you can find all supported
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syntaxes.
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Supported Literals
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~~~~~~~~~~~~~~~~~~
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The component supports:
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* **strings** - single and double quotes (e.g. ``'hello'``)
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* **numbers** - e.g. ``103``
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* **arrays** - using twig notation (e.g. ``[1, 2]``)
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* **hashes** - using twig notation (e.g. ``{ foo: 'bar' }``)
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* **booleans** - ``true`` and ``false``
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* **null** - ``null``
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Supported Operators
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~~~~~~~~~~~~~~~~~~~
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The component comes with a lot of operators:
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Arithmetic Operators
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....................
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* ``+`` (addition)
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* ``-`` (subtraction)
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* ``*`` (multiplication)
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* ``/`` (division)
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* ``%`` (modulus)
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* ``**`` (pow)
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Assignment Operators
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....................
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* ``=``
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Bitwise Operators
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.................
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* ``&`` (and)
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* ``|`` (or)
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* ``^`` (xor)
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Comparison Operators
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....................
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* ``==`` (equal)
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* ``===`` (identical)
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* ``!=`` (not equal)
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* ``!==`` (not identical)
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* ``<`` (less than)
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* ``>`` (greater than)
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* ``<=`` (less than or equal to)
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* ``>=`` (greater than or equal to)
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* ``matches`` (regex match)
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.. tip::
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To test if a string does *not* match a regex, use the logical ``not``
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operator in combination with the ``matches`` operator::
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$language->evaluate('not "foo" matches "/bar/"'); // returns true
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Logical Operators
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.................
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* ``not`` or ``!``
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* ``and`` or ``&&``
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* ``or`` or ``||``
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String Operators
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................
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* ``~`` (concatenation)
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Array Operators
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...............
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* ``in`` (contain)
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* ``not in`` (does not contain)
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Numeric Operators
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.................
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* ``..`` (range)
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Ternary Operators
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.................
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* ``foo ? 'yes' : 'no'``
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* ``foo ?: 'no'`` (equal to ``foo ? foo : 'no'``)
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* ``foo ? 'yes'`` (equal to ``foo ? 'yes' : ''``)

‎components/index.rst

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dependency_injection/index
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dom_crawler
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event_dispatcher/index
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expression_language/index
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filesystem
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finder
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form/index

‎components/map.rst.inc

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* :doc:`/components/event_dispatcher/generic_event`
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* :doc:`/components/event_dispatcher/immutable_dispatcher`
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* :doc:`/components/expression_language/index`
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* :doc:`/components/expression_language/introduction`
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* :doc:`/components/expression_language/syntax`
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* **Filesystem**
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* :doc:`/components/filesystem`

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