Hi Richard - but why would you expect 1 to: 0 to give you an empty sequence? If I inspect â0 to: 1â I see: 1 -> 0 2 -> 1 So I would expect â1 to: 0â 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 Câish. 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 <raoknz@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: [â¦
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 donât 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 Iâll correct it when I get the wisdom of the crowd here.
Tim