13 Templates [temp]

13.7 Template declarations [temp.decls]

13.7.7 Function templates [temp.fct]

13.7.7.1 General [temp.fct.general]

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A function template defines an unbounded set of related functions.
[Example 1: 
A family of sort functions can be declared like this: template<class T> class Array { }; template<class T> void sort(Array<T>&);
— end example]
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[Note 1: 
A function template can have the same name as other function templates and non-template functions ([dcl.fct]) in the same scope.
— end note]
A non-template function is not related to a function template (i.e., it is never considered to be a specialization), even if it has the same name and type as a potentially generated function template specialization.122
122)122)
That is, declarations of non-template functions do not merely guide overload resolution of function template specializations with the same name.
If such a non-template function is odr-used ([basic.def.odr]) in a program, it must be defined; it will not be implicitly instantiated using the function template definition.