Substitution failure is not an error: Difference between revisions

Revision as of 04:44, 14 September 2010

Revision as of 15:27, 21 September 2010

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When <code>T</code> has the nested type <code>type</code> defined, the instantiation of the first <code>test</code> works and 0 is successfully passed as the null pointer constant. (And the resulting type of the expression is <code>yes</code>.) If it does not work, the only available function is the second <code>test</code>, and the resulting type of the expression is <code>no</code>. (EllipsesAn areellipsis is used not only because it will accept any argument, but also because it'sits conversion rank is lowest, so a call to the first function will be preferred if it is possible; this removes ambiguity.)

Developers of [[Boost C++ Libraries|Boost]] used SFINAE to great effect in boost::enable_if<ref name="enable_if">[http://www.boost.org/doc/libs/release/libs/utility/enable_if.html Boost Enable If]</ref> and in other ways.