On 20/02/16 03:32 +0000, Jonathan Wakely wrote:
On 19/02/16 20:18 -0700, Orion Poplawski wrote:
octave has template functions that call abs() on templated
variables, something like:
template <class T>
T myfunc(T arg) {
T x = abs(arg);
}
This leads to errors when instantiated for unsigned types because
abs(unsigned type) is not defined as is doesn't make sense to do.
That's fine and all, but how then does one write generic template
code as above that works for signed and unsigned types.
template <class T>
typename std::enable_if<std::is_signed<T>::value, T>::type
generic_abs(T arg) {
return abs(arg);
}
template <class T>
typename std::enable_if<!std::is_signed<T>::value, T>::type
generic_abs(T arg) {
return arg;
}
template <class T>
T myfunc(T arg) {
T x = generic_abs(arg);
}
Or maybe better, figure out which version of abs() it used to call
before the GCC 6 changes, which was probably abs(int), and just cast
to that.
If it worked before without an overloaded abs() then implicitly
converting to int must have been OK (or a lurking bug). So just:
template <class T>
T myfunc(T arg) {
T x = abs((int)arg);
}
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