[Python-ideas] [Python-Dev] Inclusive Range (original) (raw)

MRAB python at mrabarnett.plus.com
Tue Oct 5 21:43:29 CEST 2010

On 05/10/2010 20:23, spir wrote:

On Tue, 05 Oct 2010 13:45:56 +0200 Boris Borcic<bborcic at gmail.com> wrote:

Nick Coghlan wrote: [...] Being able to say things like "10:00"<= x< '12:00", 10.0<= x< 12.0, "a"<= x< "n" are much clearer than trying to specify their closed range equivalents.

makes one wonder about syntax like : for 10<= x< 20 : blah(x)

Mh, I suppose with rich comparisons special methods, it's possible to turn chained comparisons into range factories without introducing new syntax. Something more like for x in (10<= step(1)< 20) : blah(x) About notation, even if loved right-hand-half-open intervals, I would wonder about [a,b] noting it. I guess 99.9% of programmers and novices (even purely amateur) have learnt about intervals at school in math courses. Both notations I know of use [a,b] for closed intervals, while half-open ones are noted either [a,b[ or [a,b). Thus, for me, the present C/python/etc notation is at best misleading. So, what about a hypothetical language using directly math unambiguous notation, thus also letting programmers chose their preferred semantics (without fooling others)? End of war? [Oops! Post sent to wrong list!]

Dijkstra came to his conclusion after seeing the results of students using the programming language Mesa, which does support all 4 forms of interval.

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