Template distinguish between signed and unsigned

Question

If have written a template function and the code only work correct if the template type is unsinged. Now I search for a way to prevent the fumction from compiling with signed types, without C++11.

template<typename T>
T foo() {
    T a=0;
    return a<<1;
}

score 4 · Accepted Answer · answered Sep 17 '19 at 08:50

4

std::is_signed is only available since C++11, however before you can use std::numeric_limits<T>::is_signed.

As static_assert is also C++11, you have to use something else, eg the trick from here:

typedef int static_assert_something[something ? 1 : -1];

answered Sep 17 '19 at 08:50

463035818_is_not_an_ai

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Yes, this will do nicely! – Bathsheba Sep 17 '19 at 08:56

score 0 · Answer 2 · answered Sep 17 '19 at 13:17

0

Without library: for signed types, ~T(0) < T(0) but for unsigned types, ~T(0) > T(0). These are compile-time constants. See the other answer how to turn that into an error.

answered Sep 17 '19 at 13:17

MSalters

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Template distinguish between signed and unsigned

2 Answers2