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