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Re: FOR loop ends one above where it's supposed to [message #71137 is a reply to message #71135]

Tue, 01 June 2010 17:53

mankoff
Messages: 131
Registered: March 2004

Senior Member

On Jun 1, 5:26 pm, Bulgakovv <alex.ph.sjog...@gmail.com> wrote:
> Maybe there are previous posts about this, but I tried to google
> around without any success so I'll throw the question out.
>
> When I make a FOR loop from for example 0 to 5, the counter ends on
> the value one step above what I stated. Here's an example:
>
>> for i =0,5 do print,i
>
> 0
> 1
> 2
> 3
> 4
> 5>print,i
>
> 6
>
> Is this how it's supposed to be in IDL? To me it seems a little bit
> weird, why would the FOR loop count one extra step in the end? Took me
> a couple of hours to realize what was going on in my code as I took
> for granted this was not the case, so now I'm interested in
> understanding why IDL is behaving like this. Thanks and sorry if
> reposting!

The way I think of for loops is this:
>> for i =0,5 do print,i
1) Set i = 0
2) Check if i gt 5
3) If not, do the loop
4) increment i
5) Go to step (2)

So, step 4 happens incrementing from 5 to 6 at the end of the loop,
and then it continues past the end of the loop, but no loop events
occur with i equal to 6. Every other language I have used behaves
analogous to this, I think.

-k.

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[Message index]

		Re: FOR loop ends one above where it's supposed to By: Bulgakovv on Wed, 02 June 2010 09:49
		Re: FOR loop ends one above where it's supposed to By: penteado on Wed, 02 June 2010 09:07
		Re: FOR loop ends one above where it's supposed to By: pgrigis on Wed, 02 June 2010 08:57
		Re: FOR loop ends one above where it's supposed to By: cameron bowles on Tue, 01 June 2010 22:36
		Re: FOR loop ends one above where it's supposed to By: cameron bowles on Tue, 01 June 2010 22:34
		Re: FOR loop ends one above where it's supposed to By: mankoff on Tue, 01 June 2010 17:53

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