Re: removing duplicates from container,

Richard Herring <junk@[]>
Mon, 10 Jul 2006 14:03:10 +0100
In message <dZWqg.3494$5K2.798@fed1read03>, vsgdp <>

struct S { /*...*/ };
std::set<S*> ss; // Ok

   Is it really ok? I vaguely recall something about not being allowed to
compare pointers (except for (in)equality), unless they belong to the same
array .. ?

I found something in an old post:

" Also note that others
have pointed out that comparing addresses of objects
that are not part of the same aggregrate (e.g. 'struct'
or array) with comparison operator othere than '=='
is undefined. "

My "set" will actually store pointers to elements that are in one big array,
so I guess it is okay for me to use set since I'll be comparing addresses of
elements that are part of the same array.

That's not a problem anyway, because std::set uses std::less as its
default comparison functor, and the standard (20.3.3/8) guarantees that
std::less defines a total order on pointer types even when operator <

Richard Herring

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