.. _stdlib_assert_once:

===========
Assert once
===========

The assert_once module implements single-time assertion infrastructure.

All functions and symbols are in "assert_once" module, use require to get access to it. ::

    require daslib/assert_once

++++++++++++++++++++
Function annotations
++++++++++++++++++++

.. _handle-assert_once-AssertOnceMacro:

.. das:attribute:: AssertOnceMacro

This macro convert assert_once(expr,message) to the following code::

    var __assert_once_I = true  // this is a global variable
    if __assert_once_I && !expr
        __assert_once_I = false
        assert(false,message)

+++++++++
Assertion
+++++++++

  *  :ref:`assert_once (expr: bool; message: string = "") <function-assert_once_assert_once_bool_string>` 

.. _function-assert_once_assert_once_bool_string:

.. das:function:: assert_once(expr: bool; message: string = "")

Same as assert, only the check will be not be repeated after the asseretion failed the first time.

:Arguments: * **expr** : bool

            * **message** : string