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From: Ioannis Vranos <ivr@remove.this.grad.com>
Newsgroups: comp.lang.ada,comp.lang.c++,comp.realtime,comp.software-eng
Subject: Re: [OT] Re: Teaching new tricks to an old dog (C++ -->Ada)
Date: Mon, 14 Mar 2005 17:05:43 +0200
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Date: 2005-03-14T17:05:43+02:00
List-Id: <comp.lang.ada>

Dr. Adrian Wrigley wrote:

> #include <map>
> 
> struct compoundindex {
>   int a, b, c;
> };


inline bool operator <(const compoundindex &a, const compoundindex &b)
{
     return (a.a<b.a && a.b<b.b && a.c<b.c)? true: false;
}


> int main()
> {
>     std::map<compoundindex, float> hash;
>     compoundindex fred = { 1, 2, 4 };
> 
>     hash[fred] = 0.123;
> }



As a rule of thumb remember that most standard containers and algorithms 
require the presence of operator <.


 From a design perspective, in the example above, it is better to make 
operator< a member of the struct. I made it a global function, in case 
you want a POD struct.



-- 
Ioannis Vranos

http://www23.brinkster.com/noicys