Re: [Boost-users] using if_then lambda with transform

From: Delfin Rojas (drojas_at_[hidden])
Date: 2006-03-03 20:22:03

> yinglcs2_at_[hidden] wrote
> 
> I have a vector of Rect. and I would like to copy those where 
> Rect::getX() equals to certain value.
> 
> typedef RectList list<Rect>;
> 
> void handleX(const RectList& rectList, int value, RectList& 
> destList) {
> 	
> transform(rectList.begin(), rectList.end(), 
> back_inserter(destList), if_then ( bind(&Rect::getX,
> _1)  == value , _1 ));
> }
> 

It seems what you want is copy_if. transform won't help in this case because
it will execute the predicate on every element and assign its return value
to the output iterator, try this (not tested):

for_each(rectList.begin(), rectList.end(), if_then(bind(&Rect::getX, _1) ==
value, bind(&RectList::push_back, ref(destList), _1)));

-delfin