Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
On 22/02/2019 15:57, Tim Mackinnon 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). Expectations are obviously personal, but as far as I am concerned, I'd expect to see the behavior that Pharo implements. If you don't specify by:, you get a default value of 1. That's much simpler than a default value depending on the bounds of the interval. Konrad.
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
If it’s always been that way - and things rely on it, sure. But it doesn’t feel like the Smalltalk way to me. Having to know about adding -1 seems very C, whereas Smalltalk always seems more natural ... and 5 to: 1 seems like you would count down, not be an empty range and do nothing. But as you say, it’s personal. I’m still curious though. Tim Sent from my iPhone > On 22 Feb 2019, at 16:13, Konrad Hinsen wrote: > >> On 22/02/2019 15:57, Tim Mackinnon 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). > > Expectations are obviously personal, but as far as I am concerned, I'd expect > to see the behavior that Pharo implements. If you don't specify by:, you get > a default value of 1. That's much simpler than a default value depending on > the bounds of the interval. > > Konrad. > >
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
> On 22 Feb 2019, at 22:35, Tim Mackinnon wrote: > > If it’s always been that way - and things rely on it, sure. > > But it doesn’t feel like the Smalltalk way to me. > > Having to know about adding -1 seems very C, whereas Smalltalk always seems > more natural ... and 5 to: 1 seems like you would count down, not be an empty > range and do nothing. > > But as you say, it’s personal. I’m still curious though. I personally would find it cool if 10 to: 1 counted down, it feels natural. But I must say I haven't thought it through. I do known that Interval is a class that leads to lots of discussions and disagreements. > Tim > > Sent from my iPhone > >> On 22 Feb 2019, at 16:13, Konrad Hinsen wrote: >> >>> On 22/02/2019 15:57, Tim Mackinnon 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). >> >> Expectations are obviously personal, but as far as I am concerned, I'd >> expect to see the behavior that Pharo implements. If you don't specify by:, >> you get a default value of 1. That's much simpler than a default value >> depending on the bounds of the interval. >> >> Konrad. >> >> > >
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
On 22/2/19 16:57, Sven Van Caekenberghe wrote: > >> On 22 Feb 2019, at 22:35, Tim Mackinnon wrote: >> >> If it’s always been that way - and things rely on it, sure. >> >> But it doesn’t feel like the Smalltalk way to me. >> >> Having to know about adding -1 seems very C, whereas Smalltalk always seems >> more natural ... and 5 to: 1 seems like you would count down, not be an >> empty range and do nothing. >> >> But as you say, it’s personal. I’m still curious though. > I personally would find it cool if > > 10 to: 1 > > counted down, it feels natural. But I must say I haven't thought it through. > > I do known that Interval is a class that leads to lots of discussions and > disagreements. > I agree with Tim and Sven: "bigger to: smaller" should count backwards, if we think in the way we used on a day to day expectation. Cheers, Offray
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
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 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
>
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
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 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 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
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
I would expect 1:0 to give me an empty sequence
because (a) for all other natural numbers n,
1:n gives me a sequence of n numbers, and (b)
how else am I supposed to get an empty sequence?
Under your interpretation, (x to: y) would never
be empty.
This has absolutely nothing to do with C.
As I commented, every programming language I
know except S uses a default increment of +1
in counted loops, if it allows default increments
at all. Fortran, Algol 68, Pascal, PL/I, the
seq(1) command in Unix, Haskell, the `seq'
function in Erlang, between/3 in Prolog, OCaml,
F#, InterLISP-D, and so it goes.
Fortran is an interesting case, because Fortran 66
left DO label id = lower,upper
unspecified when lower > upper and several compilers
made such loops execute once, to the point where
programmer tended to think the standard required that,
but Fortran 77 nailed it down: NO iterations in that
case.
Here's a typical use of #to:do:
s := 0.
1 to: a size do: [:i |
a at: i put: (s := (a at: i) + s)].
Why would you think it a good idea for this
to crash if the array is empty?
Smalltalk being Smalltalk, nothing stops you adding
through: end do: aBlock
self to: end by: (end < self ifTrue: [-1] ifFalse: [1])
do: aBlock.
to Integer if you really want to.
Oh, there's an ambiguity. Should
5 through 1 mean 5,4,3,2,1 or 1,2,3,4,5?
Both can be argued for.
On Fri, 1 Mar 2019 at 02:03, Tim Mackinnon wrote:
> 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 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 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
>>
>
>
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
On 28/02/19 6:33 PM, Tim Mackinnon wrote: So I would expect “1 to: 0” to see: 1 -> 1 2 -> 0. It is difficult for code to guess the intent of the coder. Did the coder intend an decreasing sequence or a stopping condition (i == end or i > end?). Perhaps, we could use an explicit selector: 5 downto: 1 to disambiguate between the two cases. Regards .. Subbu
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
Actually thats quite a good suggestion - it probably should have been: #upTo: #downTo: #to:by: In the first place (but I’m guessing this change will never happen) > On 1 Mar 2019, at 05:35, K K Subbu wrote: > > On 28/02/19 6:33 PM, Tim Mackinnon wrote: >> So I would expect “1 to: 0” to see: >> 1 -> 1 >> 2 -> 0. > > It is difficult for code to guess the intent of the coder. Did the coder > intend an decreasing sequence or a stopping condition (i == end or i > end?). > Perhaps, we could use an explicit selector: > > 5 downto: 1 > > to disambiguate between the two cases. > > Regards .. Subbu >
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
> On 1 Mar 2019, at 12:22, Tim Mackinnon wrote: > > Actually thats quite a good suggestion - it probably should have been: > > #upTo: > #downTo: > #to:by: > > In the first place (but I’m guessing this change will never happen) I like this too. Why would this not happen ? It is just one selector more. I think the only possible issue is that #to:do: is known by the compiler, which makes it faster than any other iteration, even do: - there is always a tradeoff between readability and raw speed. >> On 1 Mar 2019, at 05:35, K K Subbu wrote: >> >> On 28/02/19 6:33 PM, Tim Mackinnon wrote: >>> So I would expect “1 to: 0” to see: >>> 1 -> 1 >>> 2 -> 0. >> >> It is difficult for code to guess the intent of the coder. Did the coder >> intend an decreasing sequence or a stopping condition (i == end or i > >> end?). Perhaps, we could use an explicit selector: >> >> 5 downto: 1 >> >> to disambiguate between the two cases. >> >> Regards .. Subbu >> > >
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
On 01/03/19 5:35 PM, Sven Van Caekenberghe wrote: I like this too. Why would this not happen ? It is just one selector more. I think the only possible issue is that #to:do: is known by the compiler, which makes it faster than any other iteration, even do: - there is always a tradeoff between readability and raw speed. Thank you for the kind words. I am not sure if speed would be affected much by: downTo: stop ^self to: stop by: -1 downTo: stop do: aBlock ^self to: stop by: -1 do: aBlock In performance critical paths, one can always use to:do: with explicit steps. Regards .. Subbu
Re: [Pharo-users] Interval form: x to: y when x > y - or how to count down...
Hey - sometimes these more philosophical conversations do amount to something. I will propose to gene changes and submit a pr - as after all, Pharo is ours and pointing someone to #downTo: or #upTo: would be very rewarding (and for Richard - #to: would remain the same so everyone wins) Tim Sent from my iPhone Sent from my iPhone >> On 1 Mar 2019, at 18:30, K K Subbu wrote: >> >> On 01/03/19 5:35 PM, Sven Van Caekenberghe wrote: >> I like this too. >> Why would this not happen ? It is just one selector more. >> I think the only possible issue is that #to:do: is known by the >> compiler, which makes it faster than any other iteration, even do: - >> there is always a tradeoff between readability and raw speed. > > Thank you for the kind words. I am not sure if speed would be affected much > by: > > downTo: stop > ^self to: stop by: -1 > > downTo: stop do: aBlock > ^self to: stop by: -1 do: aBlock > > In performance critical paths, one can always use to:do: with explicit steps. > > Regards .. Subbu >
