Re: [Boost-users] [Range] Adaptors

2011/1/6 Robert Jones

On Wed, Jan 5, 2011 at 5:13 PM, Dave Abrahams wrote:

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At Wed, 5 Jan 2011 16:05:56 +0000, Robert Jones wrote:

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I might be asking for the impossible here, but given the lovely adaptor syntax, eg

std::vector<int> vec; boost::copy( vec | boost::adaptors::reversed | boost::adaptors::uniqued, std::ostream_iterator<int>(std::cout) );

Lovley syntax indeed. I am new to it, and I like it.

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I notice it still uses the function call notation in the outermost

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operation( boost::copy() ), can it be written to eliminate function call syntax completely, say something like

vec | boost::adaptors::reversed | boost::adaptors::uniqued | boost::adaptors::copy( std::ostream_iterator<int>(std::cout) );

or even

vec | boost::adaptors::reversed | boost::adaptors::uniqued | std::ostream_iterator<int>(std::cout);

+1

It could be done, but it might not make much sense. The boost

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adaptors are essentially lazy sequence transformations, but the copy operation you're asking for has a completely different nature: it's eager. If you still like that syntax, though, you could write a suitable copy function of your own in about 40 lines that would do the same job.

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?

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;

+1

the final use of operator|() seems to pretty much imply eagerness in the same way that the for_each() does.

I'm not sure that it would be possible to implement it unambiguously tho'.

- Rob.

Regards, Kris