* question about HOWTO use std::set in non-trival way...
@ 2004-09-10 23:34 Jeffrey Holle
2004-09-10 23:59 ` Eljay Love-Jensen
0 siblings, 1 reply; 3+ messages in thread
From: Jeffrey Holle @ 2004-09-10 23:34 UTC (permalink / raw)
To: gcc-help
I'm using gcc v3.4.1.
I've got an application that has a need for the following set container:
struct ltSubgraph : public binary_function<Edge,Edge,bool>
{
ltSubgraph(const SubGraphT& subgraph);
.....
};
typedef set<Edge,ltSubgraph> Edges;
The compare function requires that it has a SubGraphT object to
implement its operator() method.
The question is how do I instanciate this container?
Just doing:
Edges edges;
Produces errors for want of a ltSubgraph default constructor...
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: question about HOWTO use std::set in non-trival way...
2004-09-10 23:34 question about HOWTO use std::set in non-trival way Jeffrey Holle
@ 2004-09-10 23:59 ` Eljay Love-Jensen
2004-09-11 0:37 ` Jeffrey Holle
0 siblings, 1 reply; 3+ messages in thread
From: Eljay Love-Jensen @ 2004-09-10 23:59 UTC (permalink / raw)
To: jeff.holle, gcc-help
Hi Jeff,
Why does your ltSubgraph comparison function object class have a copy
constructor?
See section 18.4.2 of Stroustrup's C++ Programming Language (3rd or special
edition), for what a less functor object looks like.
HTH,
--Eljay
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: question about HOWTO use std::set in non-trival way...
2004-09-10 23:59 ` Eljay Love-Jensen
@ 2004-09-11 0:37 ` Jeffrey Holle
0 siblings, 0 replies; 3+ messages in thread
From: Jeffrey Holle @ 2004-09-11 0:37 UTC (permalink / raw)
To: gcc-help
Found my own answer by looking at the implementation of set in
bits/stl_set.h.
set has the approbriate constructor, so the answer is:
Edges edges(ltSubGraph(graph_)).
A very thoughtful implementation!
Eljay Love-Jensen wrote:
> Hi Jeff,
>
> Why does your ltSubgraph comparison function object class have a copy
> constructor?
>
> See section 18.4.2 of Stroustrup's C++ Programming Language (3rd or
> special edition), for what a less functor object looks like.
>
> HTH,
> --Eljay
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2004-09-10 23:34 question about HOWTO use std::set in non-trival way Jeffrey Holle
2004-09-10 23:59 ` Eljay Love-Jensen
2004-09-11 0:37 ` Jeffrey Holle
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