Re: [Boost-users] [Range] Adaptors

Subject: Re: [Boost-users] [Range] Adaptors
From: Dave Abrahams (dave_at_[hidden])
Date: 2011-01-06 09:51:50

At Thu, 6 Jan 2011 13:23:11 +0000,
Robert Jones wrote:
> 
> Yes.... I take your point about eager vs lazy, but on reflection is it not
> the case that almost any 'pipeline' of transformations has to end with
> 'eager' consumption?

No, it is not.  In some languages, everything is lazy, and the only
thing that eventually forces evaluation is I/O.  You can easily pass
around, store, and compose lazy ranges to your heart's content.

> If I had
> 
> int f( int );
> 
> boost::for_each( vec | boost::adaptors::reversed | boost::adaptors::uniqued,
> f );
> 
> and instead were able to write it as
> 
> vec | boost::adaptors::reversed | boost::adaptors::uniqued | f;
> 
> the final use of operator|() seems to pretty much imply eagerness in the
> same way that the for_each() does.

Only if you happen to know that f is a function and will be treated
completely differently from the range adaptors.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com