CODEWITHSUNDEEP
c++templatesoverloadingtemplate-specializationoverload-resolution
Bruno Santos
Bruno Santos

Reputation: 735

C++ Overloading takes precedence over Specialization?

Given the following code:

#include <iostream>

using namespace std;

template<typename T> void Print(T t) {
    cout << t << endl;
}

template<> void Print<int>(int t) {
    cout << "int = " << t << endl;
}

void Print(int i) {
    cout << "int2 = " << i << endl;
}

int _tmain(int argc, _TCHAR* argv[])
{
    Print(1.3);
    Print("tese");
    Print(2);

    char c;

    cin >> c;

return 0;
}

Why is the call Print(2) not ambiguous, but instead calling void Print(int i) ?

ps: Tested with bcc64.exe and cl.exe.

Upvotes: 6

Views: 1911

Answers (3)

Fahad Siddiqui
Fahad Siddiqui

Reputation: 1849

Because you didn't write it as Print<int> (2).

Writing it with angle brackets means you're invoking the template function. Since you didn't call the exact template function by writing angle brackets. It doesn't conflict with any of the call Print (any integer); later. Because the template function doesn't exist there at that moment.

See the C++ working draft section Name Resolution under the heading Templates. Hope it helped.

Upvotes: -2

PierreBdR
PierreBdR

Reputation: 43314

Section 13.3.3 of the standard, on choosing the best function for an overloading, explicitly states that given the choice between a templated and a non-templated function having the exact same argument list, the non-templated function is always a better fit than the templated one.

Upvotes: 4

mrks
mrks

Reputation: 8343

This is because non-template functions are first-class citizens. See this article by Herb Sutter or this SO post for details.

From Herb Sutter's article:

Nontemplate functions are first-class citizens. A plain old nontemplate function that matches the parameter types as well as any function template will be selected over an otherwise-just-as-good function template.

If there are no first-class citizens to choose from that are at least as good, then function base templates as the second-class citizens get consulted next. Which function base template gets selected depends on which matches best and is the "most specialized" (important note: this use of "specialized" oddly enough has nothing to do with template specializations; it's just an unfortunate colloquialism) according to a set of fairly arcane rules:

Upvotes: 2

Related Questions