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Re: Finding a value in a array efficiently [message #48342]

Thu, 13 April 2006 18:58

Wayne Landsman
Messages: 117
Registered: January 1997

Senior Member

"JD Smith" <jdsmith@as.arizona.edu> wrote in message
news:pan.2006.04.13.23.00.45.990566@as.arizona.edu...
> As an aside, do you avoid using BREAK instead of goto for compatibility
> with old IDL versions?
>

Actually, today I decided to set the minimum IDL version for my code to V5.4
instead of V5.3. V5.4 is when both BREAK and ARRAY_EQUAL() were
introduced. So after first updating the the GOTOs to BREAK, I started
to look if the code could be more efficient using ARRAY_EQUAL(). (I
didn't immediately realize, though, that BREAK could be safely placed
inside of an inner ENDIF clause, and it would still break out of the FOR
loop.)

>> found = 1 - array_equal( array EQ value, 0)

> Just negate your ARRAY_EQUAL. I use this all the time:
>
>in_array=~array_equal(array NE value,1b)

This is still not quite optimal since the term (array NE value) is always
evaluated for the entire array. That is why I was looking for a function,
say, ARRAY_OR for which one could write

in_array = array_or(array,value)

which would return 1 as soon as it found an element of array equal to value,
and not perform any operations on the remaining elements of the array.

--Wayne

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[Message index]

		Re: Finding a value in a array efficiently By: Wayne Landsman on Thu, 13 April 2006 18:58
		Re: Finding a value in a array efficiently By: JD Smith on Thu, 13 April 2006 16:00
		Re: Finding a value in a array efficiently By: JD Smith on Thu, 13 April 2006 15:39
		Re: Finding a value in a array efficiently By: David Fanning on Thu, 13 April 2006 13:49
		Re: Finding a value in a array efficiently By: JD Smith on Fri, 14 April 2006 11:05

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