Explain new things

``Calculator::evaluate()``

==========================

``Calculator::evaluate($expression, ...$vars)`` is a shorthand for ``Calculator::parse($expression)->calc(...$vars)``

``Calculator::evaluate($expression, $config, ...$vars)`` is a shorthand for

``Calculator::parse($expression, $config)->calc(...$vars)``

Configuration

#############

``Arokettu\ArithmeticParser\Config`` and ``Arokettu\ArithmeticParser\ConfigBuilder``

classes are used to configure the calculator and the parser (in future).

.. highlight:: php

Config is an immutable object and ConfigBuilder is a user-friendly way to set up options.

ConfigBuilder

=============

``build()``

-----------

``Arokettu\ArithmeticParser\Config`` class is used to configure the calculator and the parser (in future).

A method to create a Config object with configured parameters.

Config is an immutable object and ConfigBuilder is a user-friendly way to set up options.

``ConfigBuilder::default()``

----------------------------

``Config::default()``

=====================

The default preset used when no config is specified.

``ConfigBuilder::defaultConfig()``

----------------------------------

A prebuilt instance of the Config object for the default preset.

A shortcut for ``ConfigBuilder::default()->build()`` with a cached instance.

Functions

=========

The only configurable thing for now is a set of functions.

The function must be a callable that accepts a single float argument.

Default functions:

You can:

* Replace functions with your own list:

  ``$builder->setFunctions(['myfunc2' => fn ($a) => a ** 2]);``

* Add new functions:

  ``$builder->addFunctions(['myfunc3' => fn ($a) => a ** 3]);``

* Remove functions:

  ``$builder->removeFunctions('acos', 'asin');``

* Replace functions with your own list::

    <?php

    $config->setFunctions(myfunc2: fn ($a) => a ** 2);

* Add new functions::

    <?php

    $config->addFunctions(myfunc3: fn ($a) => a ** 3);

* Remove functions::

    <?php

    $config->removeFunctions('acos', 'asin');

Operators

=========

Operators can be unary and binary.

Operator symbol can be any string without digits.

Be wary when using latin character based operators, they are case-sensitive and may shadow variables and functions.

Default operators:

* ``+``, ``-`` in both unary and binary form. They are built-in and are not configurable.

* ``*``, ``/``.

You can:

* Replace operators with your own list::

    <?php

    $config->setOperators(

        new BinaryOperator('×', fn ($a, $b) => $a * $b, BinaryOperator::PRIORITY_MUL),

        new BinaryOperator('÷', fn ($a, $b) => $a / $b, BinaryOperator::PRIORITY_MUL),

    );

* Add new operators::

    <?php

    // assume you have factorial defined

    $config->addOperators(

        new BinaryOperator('^', pow(...), BinaryOperator::PRIORITY_POW, BinaryAssoc::RIGHT),

        new UnaryOperator('!', factorial(...), UnaryPos::POSTFIX),

    );

* Remove operators::

    <?php

    // you cannot divide by zero if you cannot divide

    $config->removeOperators('/');

Supported expressions can include:

* Unary ``+`` and ``-``.

* Binary ``+``, ``-``, ``*``, ``/``.

* Unary operators ``+`` and ``-`` with any custom operators added.

* Binary ``+``, ``-``, ``*``, ``/`` with any custom operators added. ``*`` and ``/`` can be disabled.

* Numbers, obviously.

  All numbers are cast to float internally.

* Functions.

  Function names are case insensitive alphanumeric strings that do not start with a number.

  They may have an optional ``@`` prefix.

  Functions accept a single parameter.

  Custom functions can be created with a Config object.

* Variables.