In function call, why doesn't nullptr match a pointer to a template object?

Question

Here is an example of a code that works perfectly:

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#include
#include

template< class D, template< class D, class A >         


        

Answer 1

Compiler can not deduce the second argument type because std::nullptr_t is not a pointer type.

¹ The pointer literal is the keyword nullptr. It is a prvalue of type std::nullptr_t. [Note: std::nullptr_t is a distinct type that is neither a pointer type nor a pointer to member type; rather, a prvalue of this type is a null pointer constant and can be converted to a null pointer value or null member pointer value. [§2.14.7]