.. _assert:

The assert() macro
====================

.. index:: assert

The *assert()* macro allows us to test that data passed to a function satisfies
certain criteria for which the function returns valid data as the
calling function might expect.

    ::

        #include <assert.h>
        
        assert( logical expression );


If the logical expression passed to the *assert* macro is false,
then an error message is printed and the program exits.

    ::

        #include <assert.h>
        
        int testfunction( int a )
        {
           int b;
           assert( a >= 0 );
           .
           .
           .
           assert( b >= 1 );
           return( b );
        }