| Re: no backwards compatibility in IDL 5.6 [message #34219] |
Fri, 28 February 2003 09:52  |
JD Smith
Messages: 850
Registered: December 1999
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Senior Member |
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On Fri, 28 Feb 2003 10:47:52 -0700, David Fanning wrote:
> Pavel Romashkin (pavel_romashkin@hotmail.com) writes:
>
>> Why is EXECUTE used in this program? Why can't the value just be
>> returned from each CASE? Execute will slow it down and as far as I can
>> tell, does nothing special. There is no code that follows the CASE to
>> prevent you from returning at any point. Will it not compile in 5.4
>> with the extra keyword? I thought keyword mismatches are runtime
>> errors. Am I missing something?
>
> I don't know. I got so confused with the discussion yesterday I finally
> just said the hell with it and went back to bed. :-(
>
> Let's just say I had no idea so many people used the ATAN function.
>
> I'm totally confused about when things will compile and when they won't.
> The only thing I know for sure is they won't compile if they have to.
> For example, they would never compile if you were doing a demo in front
> of the new Vice President of the company.
>
> I think there must have been a change somewhere along the way (while we
> are on this subject). Because I didn't expect that file to compile in
> IDL 5.4, due to the REAL_PART function in the IDL 5.5 part of the CASE
> statement. When it did, that's when I realized I needed a nap.
>
>
I bet you didn't change your IDL PATH between running 5.5 and 5.4.
REAL_PART is in the !DIR/lib as a .pro file, and 5.4 can use it just as
well. Also, resolving a routine call into a compiled .pro file occurs at
run-time, so even if you called it REAL_PART_DOESNT_EXIST it would still
compile.
I.e.:
pro foo
if 0 then MY_NON_EXISTENT_PROCEDURE,4
end
would compile and run perfectly fine.
IDL does check the number of arguments of *built-in* (i.e. not .pro)
system routines at compile time (this counts DLMs too). I think Pavel is
right that all keywords are checked at run-time.
JD
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