Back to General and Gameplay Programming

Help with template function parameters

null_pointer · 2002-09-16T08:24:19

I cannot figure out why the code at the end of this source listing does not compile when I call it with a literal. Can anyone help? And if so, could we please proceed from the premise that null knows what he is doing so that we can actually give definitive answers to the problem he is asking about? Much obliged; no grudges. # include <new> # include <stdexcept> using std::logic_error; // construct - invokes constructor, optionally passes arguments template <typename T> inline T* construct (void* address) { return new (address) T; } template <typename T, typename P1> inline T* construct (void* address, P1& p1) { return new (address) T (p1); } template <typename T, typename P1, typename P2> inline T* construct (void* address, P1& p1, P2& p2) { return new (address) T (p1, p2); } // destruct - invokes destructor template <typename T> inline void* destruct (T* object) { delete object; return object; } // reconstruct - invokes destructor and then constructor in-place template <typename T> inline T* reconstruct (T* object) { return construct (destruct (object)); } template <typename T, typename P1> inline T* reconstruct (T* object, P1& p1) { return construct (destruct (object), p1); } template <typename T, typename P1, typename P2> inline T* reconstruct (T* object, P1& p1, P2& p2) { return construct (destruct (object), p1, p2); } // dynamic - a class that adds dynamic construction to its T template <typename T> class dynamic { char memory [sizeof (T)]; // TODO: fix memory alignment issues T* object; // TODO: implement copying void verify () { if (not object) throw logic_error (""); } void verify_null () { if (object) throw logic_error (""); } public: dynamic () : object (0) {} ~dynamic () { if (object) ::destruct (object); } T* operator -> () { verify (); return object; } T& operator * () { verify (); return *object; } // construct void construct () { verify_null (); object = ::construct <T> (memory); } template <typename P1> void construct (P1& p1) { verify_null (); object = ::construct <T> (memory, p1); } template <typename P1, typename P2> void construct (P1& p1, P2& p2) { verify_null (); object = ::construct <T> (memory, p1, p2); } // destruct void destruct () { verify (); ::destruct (object); object = 0; } // reconstruct void reconstruct () { destruct (); construct (); } template <typename P1> void reconstruct (P1& p1) { destruct (); construct (p1); } template <typename P1, typename P2> void reconstruct (P1& p1, P2& p2) { destruct (); construct (p1, p2); } }; // example code illustrating problem struct myclass { myclass (int n) {} }; const int five = 5; int main () { dynamic <myclass> dm; dm.construct (five); //dm.construct (5) // <- this one wouldn''t work!! }

General and Gameplay Programming Programming

Started by null_pointer September 11, 2002 06:51 PM

39 comments, last by null_pointer 21 years, 7 months ago

null_pointer

289

Author

September 16, 2002 08:24 AM

quote:I''m a bit lost in this discussion so I apologize if I''m repeating stated material.

You are; apology accepted.

quote:So it''s a life long and well debated problem that you cannot take non const ref to temporaries (Search comp.lang.c++.moderated archives). The cons outweight the pros if we allow that.

I do not want to allow non-const references to temporaries; I want P1& to be detected as const when P1 is the type of a temporary being passed to the function template. Same thing for literals. String literals have a slightly different problem... See my previous post for more information about these issues.

quote:If you set it to take a const ref, then comeau compiles it happily.

(eight...)

quote:Note: Amazingly, VC++ 6 compiles it everything ! I should have known earlier to use another compiler to test.

Yeah, maybe I should have stayed with VC++ 6. j/k

Help with template function parameters

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Help with template function parameters

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Reticulating splines