Re: [Boost-users] [Range] Adaptors

Subject: Re: [Boost-users] [Range] Adaptors
From: Jeff Flinn (TriumphSprint2000_at_[hidden])
Date: 2011-01-10 11:52:55

Robert Jones wrote:
> On Thu, Jan 6, 2011 at 11:57 PM, Neil Groves <neil_at_[hidden] 
> <mailto:neil_at_[hidden]>> wrote:
> 
>     Ignoring the implementation issues for a moment I would like to
>     explain my rationale for the current syntax. I consider the range
>     adaptors to be orthogonal to algorithms. I therefore perceive a
>     syntactic difference between the application of algorithms and
>     adaptors to be an advantage. With your example above I find the
>     first version of the code more instantly understandable since the
>     most-significant operation (copy) is at the start of the line.
>     Therefore my personal opinion is that it is undesirable to extend
>     the pipe syntax to the application of algorithms.
> 
> 
> I'm not entirely convinced by the 'orthogonality' view - it is certainly 
> one way of looking at adaptors vs algorithms, and is not without
> merit, but I do find the fully piped syntax a very natural expression of 
> design intent. If the implementation difficulties were not
> prohibitive it is a syntax I'd like supported.

-1

Neil's range rationale derives from the origins of (Thorsten's)range 
library and David Abrahams' interator adaptor library, all of which IIRC 
derive from Gary Powell's View Template Library. This history has 
probably biased my viewpoint.

In my mind a(n adapted) range is a view onto some sequence of items. 
That 'view' may include filters, orders, item-transforms, etc. The 
operator| appends a transform to the view to left of the '|' returning 
another view. None of this actually creates/modifies/destroys any of the 
left most sequence's items. It's akin to creating a function object. 
Changing the meaning of operator| in this context to also 'execute' that 
function object would muddy the IMHO existing clearly defined meaning of 
such expressions.

Jeff