Forum: Ruby Integer.step is inclusive?!

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Just Another Victim of the Ambient M. (Guest)
on 2008-12-23 21:45
(Received via mailing list)
I don't know how to post the output of irb so I'll just have to describe
it but if I run the following code:

0.upto(10){ |i| puts i }

    ...I will get 11 lines of output.  This iterates eleven times.
Really?!
    Why it does this is obvious.  Integer.upto is inclusive so it
includes
both 0 and 10.  However, am I the only one who thinks this is strange
behaviour?  I mean, the ususal programming protocol is that the last
element
is not included (half-open sets, if you will) so the number of
iterations is
the difference between numbers.
    Why did Ruby turn out this way?  Thank you...
Tim G. (Guest)
on 2008-12-23 21:56
(Received via mailing list)
Just Another Victim of the Ambient M. wrote:

> 0.upto(10){ |i| puts i }
>
> ...I will get 11 lines of output

Because 0 to 10 is 11 numbers.  If you want 10 numbers, use 1.upto(10)
If you want different behavior, you can use a different looping method,
or use post or pre increment, depending if you want it to display the
last element or not.
Gary W. (Guest)
on 2008-12-23 21:58
(Received via mailing list)
On Dec 23, 2008, at 2:36 PM, Just Another Victim of the Ambient
Morality wrote:
>    Why it does this is obvious.  Integer.upto is inclusive so it
> includes
> both 0 and 10.  However, am I the only one who thinks this is strange
> behaviour?  I mean, the ususal programming protocol is that the last
> element
> is not included (half-open sets, if you will) so the number of
> iterations is
> the difference between numbers.
>    Why did Ruby turn out this way?  Thank you...

It isn't really that Ruby is this way just that the method 'upto' is
this way.
There are several other ways to iterate over an integer range:

 >> (0..4).each { |i| puts i }
0
1
2
3
4

 >> (0...4).each { |i| puts i }
0
1
2
3


 >> 4.times { |i| puts i }
0
1
2
3

 >> 0.step(4).each { |i| puts i }
0
1
2
3
4

 >> 0.step(4,2).each { |i| puts i }
0
2
4
Thomas P. (Guest)
on 2008-12-23 22:01
(Received via mailing list)
2008/12/23 Just Another Victim of the Ambient M.
<removed_email_address@domain.invalid>:
>    I don't know how to post the output of irb so I'll just have to describe
> it but if I run the following code:
>
> 0.upto(10){ |i| puts i }
>
>    ...I will get 11 lines of output.  This iterates eleven times.  Really?!

because this are eleven numbers: 0 1 2 3 4 5 6 7 8 9 10

>    Why it does this is obvious.  Integer.upto is inclusive so it includes
> both 0 and 10.  However, am I the only one who thinks this is strange
> behaviour?

why do you think a loop from 0 to 10 should exclude the upper border?

In Ada it is 'for i in 0 .. 10 loop' which is a loop from 0 to 10.

-Thomas
Just Another Victim of the Ambient M. (Guest)
on 2008-12-23 22:20
(Received via mailing list)
"Just Another Victim of the Ambient M." <removed_email_address@domain.invalid>
wrote
in message news:xab4l.3997$removed_email_address@domain.invalid...
> element is not included (half-open sets, if you will) so the number of
> iterations is the difference between numbers.
>    Why did Ruby turn out this way?  Thank you...

    D'oh!
    ...and by ".upto" I, of course, meant ".step" !
Ron F. (Guest)
on 2008-12-24 15:00
(Received via mailing list)
Thomas P. wrote:
>>    Why it does this is obvious.  Integer.upto is inclusive so it includes
>> both 0 and 10.  However, am I the only one who thinks this is strange
>> behaviour?
>
> why do you think a loop from 0 to 10 should exclude the upper border?
>
> In Ada it is 'for i in 0 .. 10 loop' which is a loop from 0 to 10.
>
> -Thomas
>
>
To show my age I can say that FORTRAN is inclusive to:

        DO 100 I = 0,10
  ...
100    CONTINUE

executes 11 times.

Many languages I know don't have looping structures of this sort but
have explicit initialization, test, post loop action things (e.g.
C/C++ for loops).  There it's idiomatic to write e.g.:

for(i =0; i < 10; i++) {..}

since int array[10]  has elements 0..9, however it's certainly not
required as
for(i =0; i<=10; i++){...}
is certainly just fine... if that's what's intended.

I go back to my mantra when using a language I'm new to.  The mantra
is based on a 'game' model of programming languages... languages are
games, they have rules.  The rules may have reasons, or they may be
arbitrary choices.  They may even be capricious in some languages
(e.g. LOLCODE see
http://www.globalnerdy.com/2007/05/28/lolcode-the-...).

But if you don't play by the rules, you lose.   If you do you might
win.  Asking for the rules to be different, doesn't help you win the
game .. so the mantra

Ruby is not xxxxx

where you can substitute for xxxxx the set of languages you are trying
to force ruby to be.

Ron
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