,prior<long_<8> > >" is illegal; the expression must be "times<typename next<int_<4> >::type,typename
I remember a thread that ran for a while on this topic, and I need to make sure I've wrapped my head around it correctly. Here are my takes on laziness: <take id="point-1"> A metafunction returns lazily if it can be used interchangeably with its return type. Numeric metatypes such as integral_c are examples of metafunctions that return lazily, e.g. "int_<6>" is the same as "typename int_<6>::type". Metafunctions such as next/prior, however, do not return lazily because they cannot be used interchangeably with their return types. For example, "times<next<int_<4> prior<long_<8> >::type>". </take> <take id="point-2"> A metafunction evaluates a certain template argument lazily if it does not require the argument to be a fully instantiated type; otherwise, the evaluation is strict. The eval_if metafunction will strictly evaluate the second argument if the first argument is equivalent to false_; otherwise, it will strictly evaluate the third argument. </take> I'm less sure about point-2 than I am about point-1. In any case, feel free to correct any knowledge deficiencies I've exhibited, to make these definitions more complete. More examples would also be a great help. Cromwell D. Enage __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com