template< class T, class L, class U > typename common_type< T const &, L const &, U const & >::type clamp(T const & x, L const & lower, U const & upper) { return x < lower ? lower : upper < x ? upper : x; }
for the use of common_type (assuming it accepts 3 parameters, which I seem to remember it did; if not, just nest); and something like
Can we please not define algorithms this way? It may be possible, but that doesn't mean its a good idea. I don't know how you could possibly prove that the algorithm preserves ordering (<) when the algorithm includes 5 possibly different types. Thats not strictly true. I do know how you can prove it preserves ordering, but I'm not going to encourage the style. Define it in terms of a single type and let conversions happen at the call type.