Re: Sorting a map<T*>
On 5/7/07 5:01 PM, in article firstname.lastname@example.org, "Markus
Schoder" <email@example.com> wrote:
On Mon, 07 May 2007 19:45:00 -0400, Pete Becker wrote:
Markus Schoder wrote:
On Mon, 07 May 2007 16:11:52 -0700, Michael wrote:
On May 7, 3:01 pm, "barcaroller" <barcarol...@music.net> wrote:
I have a set<T*> that stores pointers to objects. How can I tell
set<T*> to use the objects' operator<() and not the value of the
pointers for sorting?
There's a way to create a set with two parameters: set<MyType,
key_comp is a key comparison function you define. For example,
set<int, less<int> >.
So then you'd just need to provide the appropriate comparison function
the objects' operator<(), suitably wrapped.
Actually you need a class with an appropriate operator(). A plain
function won't do here since you cannot pass it as a template
Sure you can. Try it.
No you cannot. I guess you are confusing this with algorithms like
std::lower_bound where you can specify a predicate as a _function_
parameter. As a template parameter for std::set or std::map this does not
work. Think about it -- it needs to be a type.
But std::set's Compare type may be a function type - it does not need to be
a class type that has an overloaded operator() defined. So Pete's objection
is correct - and here is some code to demonstrate:
bool MyComp(int *a, int *b)
return *a < *b;
std::set<int*, bool (*)(int*, int*)> s(MyComp);
s.insert( new int(1) );
s.insert( new int(2) );
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