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Re: FOR loop ends one above where it's supposed to [message #71135 is a reply to message #71134]

Tue, 01 June 2010 22:34

cameron bowles
Messages: 5
Registered: May 2010

Junior Member

IDL is a little different to other languages in this regard and it
handles for loops in this manner;

1. generates the index variable (first value, in your case i=0)
2. generates limit value (last value, in your case 5, stored as a
temporary variable)
3. generates step value (in your case 1, stored as a temporary
variable)
4. checks if limit is greater than index (for positive step values, or
less than for negative increments), if so then FOR loop finishes.
5. the block of statements following the DO is executed.
6. the step value is added to the index
7. repeat steps 4->6 until step 4 fails.

the difference here is IDL only uses an index variable, a lot of other
languages uses a secondary temporary value to do the FOR conditional
check and then updates the index only if the FOR condition is
satisfied.

hope that helps,
Cam

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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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