Operators in C++ what does (::Type*)0 mean

Question

Can anyone tell me what this means?

(::Type*)0

actually it is part of this

return (is_modifytype()) ?
u.myfunction : (::Type*)0; 

Answer 1

It means "cast the integer 0 (using a C-style cast) to the type Trip* (Trip pointer) found in the global namespace (::)".

It should just use nullptr - as in

return is_modifyCurrentTrip() ?
    u.modifyCurrentTrip : nullptr; 

Note: using :: explicitly to designate the global namespace prevents the compiler from prepending any namespace names itself - this is completely irrelevant when just using nullptr though.