Hi Richard - but why would you expect 1 to: 0 to give you an empty sequence?
If I inspect “0 to: 1” I see:
1 -> 0
2 -> 1
So I would expect “1 to: 0” to see:
1 -> 1
2 -> 0.
I asked for a sequence going from 1 down to 0 (in my mind). Knowing about all
the by: -1 stuff seems very C’ish.
Of course, I get that maybe it will break peoples existing code (and maybe that
would be why it never gets changed) - but it still feels very strange. Or am I
missing something?
Tim
> On 28 Feb 2019, at 12:38, Richard O'Keefe <rao...@gmail.com> wrote:
>
> Of the couple of hundred programming languages I have
> used, there is precisely one that does what you expect
> (the S programming language, as implemented in R).
> And it is a major pain in the posterior with no upside
> that I can discern.
>
> Suppose I want a sequence of n consecutive integers
> beginning with 1. In Smalltalk, (1 to: n) does the
> job. In R, 1:n *almost* does the job. But what
> happens when n = 0? Smalltalk gives me the right
> answer: an empty sequence. R gives me (1,0). That
> means that *every* *flaming* *time* I write
> for (i in 1:n) {...}
> I have to take special care to ensure that n is not
> 0, sometimes even having to whack in an extra
> if (n > 0) for (i in 1:n) {...}
>
> Trawling through my Smalltalk code, I find that about
> 6.8% of my counted loops are by: -1,
> 0.7% of them are by: a negative number other than -1,
> 2.5% of them are by: a positive number other than 1,
> 90 % are just to:do: with no by:
> Inspecting some of the 90% showed that many of them
> would go catastrophically wrong if 1 to: 0 do:
> performed its body
>
> On Sat, 23 Feb 2019 at 03:58, Tim Mackinnon <tim@testit.works> wrote:
> I've just been caught out with Intervals - why can't you do:
> 5 to: 1 do: [ :i | Transcript show: i printString] (eg a negative interval)?
>
> if you want to iterate down a series of numbers do you really have to do:
> 5 to: 1 by: -1 do: […
>
> I always assumed that if x > y the step was automatically -1 (but its not).
>
> I asked on Discord - and someone pointed out that if you use variables it
> could be ambiguous - but is it really? I don’t know if other smalltalks do it
> this way (I vaguely recall Dolphin going down, but not sure).
>
> Either way the Interval comment should mention this - and I’ll correct it
> when I get the wisdom of the crowd here.
>
> Tim
