JuniorTheoryOccasional

What happens when you build and run this program?

C++

#include <iostream>

using Meters = double;

void print(double) { std::cout << "double"; }
void print(Meters) { std::cout << "Meters"; }

int main() {
    Meters m = 2.5;
    print(m);
}

Compile error: print(double) is defined twice

Expecting Meters: an alias is another name for double, not a new type, so print(Meters) is a second definition of print(double).
Expecting a link error: the compiler already sees both definitions in one file and stops there; the linker reports only duplicates from different files.

How could you make Meters a distinct type that print can be overloaded on?
How does using Meters = double; differ from #define Meters double?

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JuniorTheoryOccasional

What happens when you build and run this program?

C++

#include <iostream>

using Meters = double;

void print(double) { std::cout << "double"; }
void print(Meters) { std::cout << "Meters"; }

int main() {
    Meters m = 2.5;
    print(m);
}

Compile error: print(double) is defined twice

Expecting Meters: an alias is another name for double, not a new type, so print(Meters) is a second definition of print(double).
Expecting a link error: the compiler already sees both definitions in one file and stops there; the linker reports only duplicates from different files.

How could you make Meters a distinct type that print can be overloaded on?
How does using Meters = double; differ from #define Meters double?

Back to questions Open topic in roadmap →Answer it yourself — Quiz