c++ - Instantiation/Template function specialization -

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i'm reading book on c++ , reason can't seem understand template specialization (implicit template instantiation, explicit template instantiation, , explicit specialization) of functions.

to clear, don't understand need explicit template instantiation or explicit specialization when 1 declare/define non-template function, override both generic template function , specialization.

where, when, , why use explicit template instantiation and/or explicit specialization of functions?

one area useful when want overload functions different return type. not supported normal functions there no way compiler resolve ambiguity of 1 variant call. template functions can achieve this

template<typename t>  t func()  {     ... }  template<> std::string func() {     ... }  template<> bool func() {     ... }

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