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digitalmars.D - std.range.chunks with only an InputRange

reply Seb <seb wilzba.ch> writes:
tl;dr: It would be nice if `chunks` would accept only an 
InputRange too.

Let me show you a common pattern that I often use:

We want to iterate over two lines in a pair and compute the 
difference between them, e.g.

```
1 2
2 3
```
=> 2

stdin.byLine.map!(x => x.split(' 
').map!(to!int)).chunks(2)).map(x =>
   abs(x.front.sum - x.dropOne.front.sum);
);

This currently doesn't compile, because `chunks` doesn't buffer, 
it saves the state of the forward range. However adding support 
for normal Input Ranges  can easily done using a buffer - it will 
of course require more memory as the .save implementation, 
however handling of ForwardRanges won't be affected.

I have seen this has been discussed more often [2,3]. The only 
argument against it was in [3] the missing manpower.
However I have already written such a simple buffering [4] in the 
past and would be happy to wrap this up nicely and (hopefully) 
bring it into a "phobos" shape - any thoughts/concerns?

[1] https://issues.dlang.org/show_bug.cgi?id=15759
[2] https://issues.dlang.org/show_bug.cgi?id=6621
[3] 
http://forum.dlang.org/post/omkpvigktgrgbzemhhuc forum.dlang.org
[4] 
https://github.com/greenify/d-itertools/blob/4afbc804e8b50c797fa206969dc3b4934911a0b9/source/splitwise.d
Mar 04 2016
parent reply Tamas <user dlang.io> writes:
I just run into this. Would be nice to have this! There's no 
reason why chunks should only work on ForwardRanges.
Mar 14 2016
parent Seb <seb wilzba.ch> writes:
On Monday, 14 March 2016 at 17:38:45 UTC, Tamas wrote:

 I just run into this. Would be nice to have this! There's no 
 reason why chunks should only work on ForwardRanges.


I opened a PR for this: 
https://github.com/D-Programming-Language/phobos/pull/4060
However I guess a proper library solution would be to extend 
`cache` to turn an InputRange into a ForwardRange (as suggested).
Mar 14 2016