4 ms·

Would someone be kind to explain how the transpiler/compiler knows that num of T1 generic(?) type can be used with the <= operator? Or that something the user

• morgenkaffee 11y ago
  It is all magic of Clang or GCC. Once you call the template with T1 the C++ compiler will enforce that your passed type supports the <= operator.
• inglor 11y ago
  This is how C++ templates work. They are a form of polymorphism through how you use the object and not based on its type. If you pass a type that cannot be used with the <= operator it will error in compile time. Being able to do this is part of why C++ templates are much more powerful than Java/C# generics and why they enable a different (and alternative) form of polymorphism to inheritance and explicit interfaces.
  • seivan 11y ago
    I see. In e.g Swift, you'd have to define before hand that T1 could be used with <= while here I guess it adds in the method for "each" T1 that could be used with it. I assume this just duplicates the method for each type at compile time instead of at runtime try to figure it out? Damnit, now I wanna rewrite back to C++.
    • jschwartzi 11y ago
      In C++ it just prints an error message and halts compilation if you try to use a type which doesn't support the semantics of the template function. It does not add functions which are not declared already.
    • aldanor 11y ago
      That's what C++ concepts are for (maybe we'll see them in C++17).