Hi,
I am having some problems with for_each:
class Universe
{
public:
bool CheckIsValidImprovement( Improvement* );
bool ValidateTech();
list<TechImprovement> techImprovements
};
class Improvement
{
};
class TechImprovement : public Improvement
{
};
I have written a
bool Universe::ValidateTech()
{
for( it = techImprovements.begin(); it != techImprovements.end();it++)
if( ! CheckIsValidImprovement(&(*it)) ) return false;
return true;
}
but I'd like to write it as a for_each or a find_if for practice but am
struggling with the error msgs!
find_if( techImprovements.begin(),
techImprovements.end(),
ptr_fun( &CheckIsValidImprovement ) );
can't use it because its a member function.
how is this problem normally solved? do you need bind second to the Universe
using a this pointer? Have I got the wrong end of the stick??
Regards
Mike
5  3878 
"Michael" <sl***********@hotmail.com> wrote in message
news:cu**********@hercules.btinternet.com... Hi,
I am having some problems with for_each:
[snip]
but I'd like to write it as a for_each or a find_if for practice but am
struggling with the error msgs!
find_if( techImprovements.begin(),
techImprovements.end(),
ptr_fun( &CheckIsValidImprovement ) );
can't use it because its a member function.
how is this problem normally solved? do you need bind second to the
Universe using a this pointer? Have I got the wrong end of the stick??
Look up 'mem_fun', 'mem_fun1', 'mem_fun_ref', 'mem_fun1_ref'
Book recommendation: www.josuttis.com/libbook
-Mike
On Tue, 8 Feb 2005 16:53:30 +0000 (UTC) in comp.lang.c++, "Michael"
<sl***********@hotmail.com> wrote, find_if( techImprovements.begin(),
techImprovements.end(),
ptr_fun( &CheckIsValidImprovement ) );
can't use it because its a member function.
how is this problem normally solved? do you need bind second to the Universe
using a this pointer?
No, you need std:mem_fun to bind with an instance.
Stroustrup section 18.4.4.2
Or perhaps boost::mem_fn or boost::bind from http://boost.org
Michael wrote: Hi,
I am having some problems with for_each:
class Universe
{
public:
bool CheckIsValidImprovement( Improvement* );
bool ValidateTech();
list<TechImprovement> techImprovements
};
class Improvement
{
};
class TechImprovement : public Improvement
{
};
I have written a
bool Universe::ValidateTech()
{
for( it = techImprovements.begin(); it != techImprovements.end();it++)
if( ! CheckIsValidImprovement(&(*it)) ) return false;
return true;
}
but I'd like to write it as a for_each or a find_if for practice but am
struggling with the error msgs!
find_if( techImprovements.begin(),
techImprovements.end(),
ptr_fun( &CheckIsValidImprovement ) );
can't use it because its a member function.
Then use mem_fun. This should work:
find_if(techImprovements.begin(), techImprovements.end(),
bind1st(mem_fun(&Universe::CheckIsValidImprovement ), this));
"Rolf Magnus" <ra******@t-online.de> wrote in message
news:cu*************@news.t-online.com... Michael wrote:
Hi,
I am having some problems with for_each:
class Universe
{
public:
bool CheckIsValidImprovement( Improvement* );
bool ValidateTech();
list<TechImprovement> techImprovements
};
class Improvement
{
};
class TechImprovement : public Improvement
{
};
I have written a
bool Universe::ValidateTech()
{
for( it = techImprovements.begin(); it !=
techImprovements.end();it++) if( ! CheckIsValidImprovement(&(*it)) ) return false;
return true;
}
but I'd like to write it as a for_each or a find_if for practice but am
struggling with the error msgs!
find_if( techImprovements.begin(),
techImprovements.end(),
ptr_fun( &CheckIsValidImprovement ) );
can't use it because its a member function.
Then use mem_fun. This should work:
find_if(techImprovements.begin(), techImprovements.end(),
bind1st(mem_fun(&Universe::CheckIsValidImprovement ), this));
Ah ha! however I now have a level of indirection problem, as the original
vector stores instances but the function needs a pointer. Is there a way of
doing the equivalen of '&'??
Regards
Michael
"Michael" <sl***********@hotmail.com> wrote in message
[snip] {
public:
bool CheckIsValidImprovement( Improvement* );
bool ValidateTech();
list<TechImprovement> techImprovements
};
[snip]
for( it = techImprovements.begin(); it != techImprovements.end();it++) if( ! CheckIsValidImprovement(&(*it)) ) return false;
return true;
Why don't you rewrite
bool CheckIsValidImprovement( Improvement* )
as
bool CheckIsValidImprovement( Improvement & )
because you have a list of objects, not pointers, anyway, and use
mem_fun_ref
as someone told you in the first reply ? ;)
HTH This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
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