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## Macro BOOST_VMD_ASSERT

BOOST_VMD_ASSERT — Conditionally causes an error to be generated.

## Synopsis

    // In header: <boost/vmd/assert.hpp>

    BOOST_VMD_ASSERT(...)

## Description

... = variadic parameters, maximum of 2 will be considered. Any variadic parameters beyond the maximum of 2 are just ignored.

The first variadic parameter is:

cond = A condition that determines whether an assertion occurs. Valid values range from 0 to BOOST_PP_LIMIT_MAG.

The second variadic parameter (optional) is:

errstr = An error string for generating a compiler error when using the VC++ compiler. The VC++ compiler is incapable of producing a preprocessor error so when the 'cond' is 0, a compiler error is generated by outputting C++ code in the form of:

    typedef char errstr[-1];

The errstr defaults to BOOST_VMD_ASSERT_ERROR if not supplied. It is only relevant for VC++.

returns = If cond expands to 0, this macro causes an error. Otherwise, it expands to nothing. For all compilers other than Visual C++ the error is a preprocessing error. For Visual C++ the error is caused by output invalid C++: this error could be masked if the invalid output is ignored by a macro which invokes this macro.