Description

The macro checks that the sequence is an identifier. If it is not an identifier, it forces a compiler error.

The macro normally checks for an identifier only in debug mode. However an end-user can force the macro to check or not check by defining the macro BOOST_VMD_ASSERT_DATA to 1 or 0 respectively.

... = variadic parameters

The variadic parameters are:

sequence = A sequence to test as an identifier.
ids (optional) = The data may take one of two forms: it is either one or more single identifiers or a single Boost PP tuple of identifiers.

returns = Normally the macro returns nothing. 

          If the sequence is an identifier, nothing is 
          output. If optional ids are specified, for the 
          sequence to be an identifier it must be an
          identifier that matches one of the optional
          ids.
          
          For VC++, because there is no sure way of forcing  
          a compiler error from within a macro without producing
          output, if the sequence is not an identifier the 
          macro forces a compiler error by outputting invalid C++.
          
          For all other compilers a compiler error is forced 
          without producing output if the sequence is not an
          identifier.

Identifiers are registered in VMD with:

#define BOOST_VMD_REG_XXX (XXX) where XXX is a v-identifier.

The identifier must be registered to be found.

Identifiers are pre-detected in VMD with:

#define BOOST_VMD_DETECT_XXX_XXX where XXX is an identifier.

If you specify optional ids and have not specified the detection of an optional id, that id will never match an identifier.