[boost] Using BOOST_ASSERT to check numeric_limits<FPT>::epsilon

From: Paul A Bristow (pbristow_at_[hidden])
Date: 2006-02-11 06:25:55

Can anyone help me insert a compile time check on the validity ( > 0) of

std::numeric_limits<FPT>::epsilon().

In this code (in floating_point_comparison.hpp)

template<typename FPT>
bool
operator()(FPT left, FPT right)
{ // ((left-right)/left) / epsilon)

  BOOST_STATIC_ASSERT(std::numeric_limits<FPT>::is_specialized); // OK.
  BOOST_STATIC_ASSERT(numeric_limits<FPT>::is_iec559); // OK
  BOOST_STATIC_ASSERT((DBL_EPSILON > 0)); // OK too.
  BOOST_STATIC_ASSERT(DBL_EPSILON); // OK, but I am trying to check for UDT
FPT

  BOOST_STATIC_ASSERT(numeric_limits<FPT>::epsilon()); // Fails to compile
  BOOST_STATIC_ASSERT(numeric_limits<FPT>::epsilon() > (FPT)0); // as does
this.

// error C2975: 'x' : invalid template argument for
'boost::STATIC_ASSERTION_FAILURE', expected compile-time constant expression

(I could just return false but this would help the user much).

  return ...;
}

epsilon should be a constant known at compile time?
But is the compile unable to know this?

Other suggestions on how to achieve a compile-time warning here?

Thanks

Paul

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