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Subject: [Boost-users] C++ guru required!
From: Robert Ramey (ramey_at_[hidden])
Date: 2012-02-17 15:40:12

I've got a really dumb question. My question is illustrated by the
code snippit.

template<class T, class U>
T inline operator%(const T & lhs, const U & rhs) {
  if(0 == rhs)
    throw std::domain_error("Divide by zero");
  if(boost::is_same<T, boost::uintmax_t>::value
  && boost::numeric::is_signed<U>::value
    if(1 == rhs || -1 == rhs) // is this dropped?
      overflow("unsigned type can hold this result");
  return lhs % rhs;

I would like to think that the second if is always
dropped from the compile for a particular pair
of types since this can be evaluated at compile time.

If I'm correct, I can replace some tedious
template metaprogramming for some straightforward
and transparent code inserted in a convenient code
inserted in the most convenient place.

Andre Alex... gave a talk at "Going Native" proposing
a "static if" for this case. But I don't see the necessity for
for this since I would assume that the compiler
just optimises away the "dead" code. I've compiled
the above and it seems to do what I want but
still I wonder.

Basically I see lots of applications of variations
on this idea to get the benefits of tmp without
the attendent pain.

Am I missing anything here?

Robert Ramey

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