[Boost-users] How to use bind/lambda in a conditional for_each?

From: Baranowski, Daniel (dbaranowski_at_[hidden])
Date: 2006-09-08 02:56:11

Hey all!

I've really enjoyed using boost::bind for calling member functions and
such. I wish I had found this earlier!

Anyhow, I'm trying to write for_each statement that only passes the
object to a function if certain conditions are met. Unfortunately, I'm
not well versed enough in boost::bind (and I've never used the lambda
library) so I'm not sure how to do this! Can someone lend me a hand? I
couldn't find anything in the mail archives.

If I were writing a regular for-loop, this is how it would look:
   vector<MyObjClass> myVector;
   myVector.push_back(MyObjClass(2));
   myVector.push_back(MyObjClass(3));
   myVector.push_back(MyObjClass(3));
   myVector.push_back(MyObjClass(5));
   myVector.push_back(MyObjClass(6));

   vector<MyObjClass>::iterator end = myVector.end();
   vector<MyObjClass>::iterator itr;
   for(itr = myVector.begin(); itr != end; ++itr)
   {
      if((*itr).GetValue() == 3)
         ProcessingFunction(*itr);
   }

And here's the for_each that just passes every object into the
processing function:
   // From inside a function in a class called ThisClass
   vector<MyObjClass> myVector;
   myVector.push_back(MyObjClass(2));
   myVector.push_back(MyObjClass(3));
   myVector.push_back(MyObjClass(3));
   myVector.push_back(MyObjClass(5));
   myVector.push_back(MyObjClass(6));

   vector<MyObjClass>::iterator begin = myVector.begin();
   vector<MyObjClass>::iterator end = myVector.end();
   
   for_each(begin, end, 
      boost::bind(&ThisClass::ProcessingFunction, this, _1));

So I guess the question is, how do I add the condition into the
for_each? I know there's got to be a way!

Thanks for any help!
Daniel
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