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Re: AND statements [message #14499 is a reply to message #14494]

Mon, 01 March 1999 00:00

steinhh
Messages: 260
Registered: June 1994

Senior Member

In article <36D9C642.99878C2A@geocities.com> Phil Aldis
<philaldis@geocities.com> writes:

> Hi,
> If you write some code like this:
>
> test=Ptr_New()
>
> IF Ptr_Valid(test) AND Size(*test, /type) NE 10 THEN print, *test
>
> ....can you always guarantee that it will not try to evaluate the second
> statement if the first one was false - or is this a dangerous tactic to
> adopt?

Nope. In fact, I can guarantee that it *will* evaluate the whole
logical expression. IDL is in this respect totally unlike C.

If the urge is big enough, one could ask RSI nicely to implement
operators like "AND THEN" and "OR ELSE" used like this:

IF ptr_valid(test) AND THEN size(*test,/type) ne 10 then print,*test

IF error_occurred OR ELSE check_for_error() then print,"Error"

"AND THEN" works like C &&
"OR ELSE" works like C ||, i.e. check_for_error() isn't called
if "error_occurred" is already true.

Operators with such names exist in e.g. Simula, IIRC.

I wouldn't be holding my breath, though.

Regards,

Stein Vidar

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[Message index]

		Re: AND statements By: Steve Scheele on Fri, 05 March 1999 00:00
		Re: AND statements By: Steve Scheele on Wed, 03 March 1999 00:00
		Re: AND statements By: steinhh on Mon, 01 March 1999 00:00
		Re: AND statements By: philaldis on Mon, 01 March 1999 00:00
		Re: AND statements By: steinhh on Mon, 01 March 1999 00:00

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