What is the value of i (that is not a constant) at compile time? There is no way to answer unless executing the loop. But executing is not “compiling” Since there is no answer, the compiler cannot do that. Templates are not algorithm to be executed, but macros to be expanded to produce code. What … Read more
Enumerations can be template parameters in exactly the same way that ints can. enum Enum { ALPHA, BETA }; template <Enum E> class Foo { // … }; template <> void Foo <ALPHA> :: foo () { // specialise } class Bar : public Foo <BETA> { // OK } But you simply haven’t provided … Read more
The reason you can’t do this is because non-constant expressions can’t be parsed and substituted during compile-time. They could change during runtime, which would require the generation of a new template during runtime, which isn’t possible because templates are a compile-time concept. Here’s what the standard allows for non-type template parameters (14.1 [temp.param] p4): A … Read more