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Upp::Sort(begin, end, less) does not compile under MSC8 when less is a plain C function [message #29372]

Sat, 16 October 2010 12:35

Didier
Messages: 736
Registered: November 2008
Location: France

Contributor

Hi all,

I stumbled accross an unexpected compile error that appears only when compiling with MSC8: no problem with GCC.

There is an easy workaround using a functor instead of a plain C compare function.

Is it an MSC8 limitation or a GCC added feature ?!?

Here is a sample code:

#include <Core/Core.h>

using namespace Upp;

typedef Pointf  XY;


bool CompareXY_x(XY a, XY b)
{
	return (a.x < b.x);
}


struct MyLessFunctor {
	bool operator () (const XY& a, const XY& b) const
	{
		return CompareXY_x(a, b);
	}
};

CONSOLE_APP_MAIN
{
	typedef Vector<XY> PointsType;
	
	
	PointsType points;
	
	points << XY(1,2) << XY(2,2) << XY(3,2) << XY(4,2) << XY(6,2);

	Sort(points, CompareXY_x); // Compile on GCC only
	Sort(points, MyLessFunctor() );// compiles on GCC and MSC8
}

[Updated on: Sat, 16 October 2010 12:37]

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Re: Upp::Sort(begin, end, less) does not compile under MSC8 when less is a plain C function [message #29376 is a reply to message #29372]

Sat, 16 October 2010 13:02

Didier
Messages: 736
Registered: November 2008
Location: France

Contributor

Besides this compile issue (which is not really an issue I think).

There is another problem: the sort algorithm is not completely exact:

	while((count = (int)(end - begin)) > __SORT_THRESHOLD) {

The only test that is valid to do on iterators is:
iter1 != iter2 (and of course iter1 == iter2 )

The operation 'end - begin' on iterators is not generic: it may work for the Upp containers, but with others .... ?

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