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Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams
From: |
Clément Pit--Claudel |
Subject: |
Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams |
Date: |
Tue, 13 Sep 2016 21:24:34 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 |
Hi Michael,
On 2016-09-13 17:17, Michael Heerdegen wrote:
> Yes, I want to forbid them, unless there are realistic use cases.
> No, we don't have something like `tail' for streams. If you want
> something like that, you are in general better done with lists (i.e.
> convert the stream into a list), I think.
I don't think converting to list would be a good idea. When operating on text
files, for example, it's often convenient to get the last n lines of a file.
If the file is represented as a stream of lines, then tail makes sense.
Doesn't it? Converting the file to a list of lines beforehand sounds like a
bad idea, memory wise.
> Streams are a mean to program in a certain way (called data flow
> control or something like that). Negative indexes for `seq-subseq'
> collide with this model.
I don't see why; isn't it common to implement slyding-window-style algorithms
on data streams? 'tail' is just one such example.
I do agree, however, that the return value of these silding-window algorithms
is not commonly a stream (rather a list, or a function of that list). But I'm
not sure that this is enough to make subseq with negative arguments irrelevant.
Otherwise, what's a point of subseq vs. e.g. drop + take?
Let me know what you think of the 'last n lines of a file' example. Maybe I'm
missing something :)
Cheers,
Clément.
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- [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Michael Heerdegen, 2016/09/13
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Clément Pit--Claudel, 2016/09/13
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Michael Heerdegen, 2016/09/13
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams,
Clément Pit--Claudel <=
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Michael Heerdegen, 2016/09/14
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Clément Pit--Claudel, 2016/09/14
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, John Mastro, 2016/09/14
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Clément Pit--Claudel, 2016/09/14
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, John Mastro, 2016/09/15
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Michael Heerdegen, 2016/09/15
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Clément Pit--Claudel, 2016/09/15
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Michael Heerdegen, 2016/09/15
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Clément Pit--Claudel, 2016/09/15
- Re: [PATCH] Elpa: Pinpoint semantics of `seq-subseq' for streams, Michael Heerdegen, 2016/09/14