Proposal: Add singleton function to Data.List module

[David Duke]

Whilst taking the point, could I just  pit out that, its not just about the
form of the final program. One of the
strengths and appeals of FP id the opportunity for program transformation
via a useful
repertoire of algebraic law, cf the work on Squiggol, and the numerous
pearls by folk including Richard Bird et.al..
This work befits from having concisely-expressed rules that open the road
to manipulation - long-winded
identifiers suitable for large libraries are not necessarily ideal here.
Going back to the original proposal, I'm not bothered, I would probably
just ignore a singleton library
in favour of  :[]. I'm -1 on philosophical grounds.
I'm used to teaching FP to undergrads and half the battle is encouraging
people to think functionally, to
make use of the underlying mathematics and computational model rather than
transliterate
Python or <insert your favourite 'bete noir'> into Haskell. That means
thinking of building programs from
functional fragments combined by suitable glue, and appreciating that data
constructors can be used
as functions Yes takes beginner's time to recognise some of the patterns,
but when the light dawns,
the transformation is rewarding. I've lost count of the number of jaws I've
had to pick off the floor :)

So I don't want to make a mountain out of a molehill. If it will really
improve people's programming
lives then fine, But I' not convinced, and but in fretting over final code
can we please not   lose
sight of the larger picture and battle..


regards
David Duke.

On Fri, Aug 16, 2019 at 3:21 PM Ignat Insarov <kindaro at gmail.com> wrote:

> I'd like to derail this conversation into remembering the "C, Unix hoax"
> joke.
> https://www.gnu.org/fun/jokes/unix-hoax.html
>
> > We stopped when we got a clean compile on the following syntax:
> >
> >     for(;P("\n"),R--;P("|"))for(e=C;e--;P("_"+(*u++/8)%2))P("|
> "+(*u/4)%2);
>
> We humans find it easier to think in words, which are singleton blobs
> of sense requiring no parsing, no compilation, but immediately
> obvious. The "monkey face" here is not one, not two, but four distinct
> blobs. This is in fact a technical argument against it, though
> referring to the technic of human cognition rather than machine's.
>
> In this perspective, is it not clear that we should strive away from
> symbol soup idioms? Let us write programs for people to read.
>
> On Mon, 12 Aug 2019 at 20:03, Herbert Valerio Riedel <hvriedel at gmail.com>
> wrote:
> >
> > > - `(:[])`: Subjectively ugly.
> >
> > I consider "subjectively ugly" to be a non-technical and thus really
> > weak argument to dismiss the list-idiomatic ninja-robot-operator (:[])
> > which also happens to be shorter than the proposed alias for it. I for
> > one don't see a significant benefit for adding a redundant synonym to
> > `Data.List` and are thus -1 on this.
> >
> > > singleton :: a -> [a]
> > > singleton x = [x]
> > _______________________________________________
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-- 
David Duke
Professor of Computer Science
School of Computing University of Leeds UK
E:duke.j.david at gmail.com
W:https://engineering.leeds.ac.uk/staff/334/Professor_David_Duke
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