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Re: how does it evaluate: y * w # A where: [message #36349 is a reply to message #36348]

Mon, 08 September 2003 07:26

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

iqbal_hassan@extenprise.net (Hassan Iqbal) writes:

> Hi,
> Please help me to understand as to how it is being evaluated and what
> do I get from this entire operation:
>
> x= y * w # A
>
> where:
>
> y= an array of 'n' elements
> w= an array of 'n' elements
> A= a matrix of 'n' columns and 'm' rows
>
> which operation is performed first: y*w or w # A

You've been asking this question, or ones like it, several times in
the past few days. Why not perform some experiments for yourself?

For example, you could practice with these two expressions:
x1 = (y * w) # A
x2 = y * (w # A)
Do both expressions work? If yes, are X1 and X2 different? If both
expressions don't work, can you see why?

Your current question is about associativity. Many languages have
left-to-right associativity, which means that operations with equal
precedence are paired left-first. Do you think that is true for IDL?

However, different operators can have different precedences. Can you
see what would happen if "*" (multiplication) were to be changed to
"+" (addition)? Perhaps the "Operator Precedence" section of the IDL
manual would help figure that one out.

Good luck,
Craig

--
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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		Re: how does it evaluate: y * w # A where: By: iqbal_hassan on Wed, 10 September 2003 02:12
		Re: how does it evaluate: y * w # A where: By: David Fanning on Mon, 08 September 2003 17:44
		Re: how does it evaluate: y * w # A where: By: Craig Markwardt on Mon, 08 September 2003 16:28
		Re: how does it evaluate: y * w # A where: By: David Fanning on Mon, 08 September 2003 07:43
		Re: how does it evaluate: y * w # A where: By: David Fanning on Mon, 08 September 2003 07:36
		Re: how does it evaluate: y * w # A where: By: Craig Markwardt on Mon, 08 September 2003 07:26

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