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Template function not called

I overloaded a function in my string class, however it never gets called. Why?

template <class T> class StringT { public: void assign(const T* ptr); template <size_t N> void assign(const T(&ptr)[N]); }; int main() { StringT<char> str; str.assign("Hello World"); //calls "void assign(const T* ptr)" although type is (const char[12]) }
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For more information, some specific references to the standard:

13.3.3 Best Viable Function

Given these definitions, a viable function F1 is defined as a better function than another viable function F2, if for all arguments i ICSi (F1) is not a worse conversion sequence than ICSi (F2), and then ...

  • F1 is not a specialized template, and F2 is not a specialized template function ...

In this case, the non-template function (obviously) is not a specialized template function, and the conversion of "Hello World" to char const* no worse than const char[N] , for the ranking rules defined in the table in the section "Standard conversion sequences" . According to this table, both No conversions required and Array-to-pointer conversion are considered exact matches in the context of overload resolution. Similarly, if template overloads are changed to overload without a template (ie Like void assign(const T(&ptr)[12]); ), compilation str.assign("Hello World"); will fail due to an ambiguous call.

To ensure that the non-template function is not considered for overloading, there is the following note in the "Explicit Specification of Template Arguments" section:

Note. The list of empty templates can be used to indicate that this use is related to the specialization of a function template, even if a function without a template is visible (8.3.5), which would otherwise be used.

So you can use str.assign<>("Hello World"); for this.

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When there is a choice, the compiler chooses the most specialized function. When there is a function without a template, than it is considered as more specialized than any template function

Details here

If you want to save the function without a template, but force the template to be called, try

 str.template assign("Hello World");
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