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The hi(static_assert)
verb( static_assert(constant expression, error message))
utility is available to allow assertions to be made from inside template
definitions. Here are two examples of its use:
verb( static_assert(BUFSIZE1 == BUFSIZE2,
"BUFSIZE1 and BUFSIZE2 must be equal");
template <typename Type1, typename Type2>
void rawswap(Type1 &type1, Type2 &type2)
{
static_assert(sizeof(Type1) == sizeof(Type2),
"rawswap: Type1 and Type2 must have equal sizes");
// ...
})
The first example shows how to avoid yet another preprocessor directive
hi(preprocessor directive: error vs. static_assert)
(in this case the ti(#error) directive).
The second example shows how tt(static_assert) can be used to ensure that
a template operates under the right condition(s).
The string defined in tt(static_assert)'s second argument is displayed and
compilation stops if the condition specified in tt(static_assert)'s first
argument is tt(false).
Like the tt(#error) preprocessor directive tt(static_assert) is a
i(compile-time) matter that doesn't have any effect on the i(run-time)
efficiency of the code in which it is used.
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