C++ for Scientists - Technische Universität Dresden

4.6. TEMPLATE SPECIALIZATION 103
class vector bool proxy
{
vector bool proxy& operator=(bool b)
{
if (b)
byte|= mask;
else
byte&= ∼mask;
return ∗this;
}
};
If our argument is true we ‘or’ it with the mask, i.e. on the considered position the one bit in
the mask turns on the bit in the byte reference and in all other positions the zero bits in the
mask leave the according positions unchanged. Reversely with a false argument, we first invert
the mask and ‘and’ it with the byte reference so that the mask’s zero bit on the active position
turns the bit off and on all other positions the ‘and’ with one bits conserves the old bit values. 8
4.6.2 Specializing a Function to a Specific Type
Functions can be specialized in the same manner as classes. Assume we have a generic function
that computes the power x y and want specialize this one:
template
Base inline power(const Base& x, const Exponent);
template
double inline power(const double& x, const double& y); // Do not use this
Unfortunately many of such specializations are ignored. Therefore, we give the following
Advise
Do not use function template specialization!
To specialize a function to one specific type or type tuple as above, we can simply use overloading.
This works better and is even simpler. Back to our example, assume we have an entirely
generic power method. 9 In the case that both arguments are double we want nevertheless use
the standard implementation hoping that some caffeine-drugged geeks figured out an incredibly
fast assembler hack for our platform and put it in our Linux distribution. Excited by the
incredible performance — even if it is only the hope for it — we overload our power function
as follows:
#include
template
Base inline power(const Base& x, const Exponent)
8 TODO: picture
9 TODO: Anybody an idea for an implementation? Or a better example?