Switch statement in c++/java: "case values"

Question

why in c/c++ and java case values should be compile-time constant?!
and what's difference between multiple if and switch statement at speed of program?
i didn't see any notable difference(with multiple if statement) in generated assembly code!

Answer 1

Martin Taylor
ok. i see.
thanks.

Answer 2

Martin Taylor Yeah.
actually i meant multiple if-else.
thank you.

Answer 3

Martin Taylor
i know compiler resolve sizeof(staticarray) at compile time.
but How does the program remember the length of the dinamic array?
delete[] arr;
i think it needs to know how many bytes are allocated. (to free them)

Answer 4

Martin Taylor oh I thought there's no runtime management in c++.
thanks.