comp.lang.idl-pvwave archive: archive » Does this make sense? (scalar objects)

Home » Public Forums » archive » Does this make sense? (scalar objects)

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Does this make sense? (scalar objects) [message #37251 is a reply to message #37183]

Fri, 05 December 2003 09:55

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Fri, 05 Dec 2003 02:58:05 -0700, Marc Schellens wrote:

>> I cannot guess any example about which (IDL) code would be broken, if
>> single element vectors and scalars would be treated the same. Do you
>> have an example?
>> Or did you mean binary code linked to IDL?
>
> Sorry, please forget. I read your reply not careful enough. As you were
> talkin gabout the abolishment of scalar type, of course you are right.
> Nevertheless, apart from indexing there should not be any difference in
> behaviour.

For objects, it's quite clear why you can't apply methods across a
vector of object variables:

IDL> objs=[obj_new('IDL_Container'), obj_new('MyFooObj')]
IDL> objs->DoSomeMethod ; WRONG

Since objects are generic pointers, and a vectors of objects can
contain any combination of object classes, it's clear why you can't
use this notation. The same is true of pointer arrays, for nearly the
same reasons:

IDL> ptrs=[ptr_new('string'),ptr_new(indgen(5))]
IDL> print,*ptrs+5 ;WRONG

Single element vectors are different than scalars in several ways:
they can be transposed, reformed, and rebinned, whereas scalars
cannot, and they can have matrix multiplications applied to them, etc.
A better way of asking the question is "What can't you do with scalars
that you can do with vectors?". The answer to this consists of the
long list of IDL vector operations discussed here daily. There may not
be any *useful* distinctions between scalars and single-element vectors,
but there are certainly plenty of programmatic distinctions, which would
break backward compatibility if ignored --- hence, we are stuck with
both.

JD

Report message to a moderator

[Message index]

		Does this make sense? (scalar objects) By: marc schellens[1] on Wed, 03 December 2003 06:33
		Re: Does this make sense? (scalar objects) By: JD Smith on Mon, 08 December 2003 10:34
		Re: Does this make sense? (scalar objects) By: marc schellens[1] on Mon, 08 December 2003 07:10
		Re: Does this make sense? (scalar objects) By: marc schellens[1] on Sat, 06 December 2003 00:33
		Re: Does this make sense? (scalar objects) By: JD Smith on Fri, 05 December 2003 09:55
		Re: Does this make sense? (scalar objects) By: marc schellens[1] on Fri, 05 December 2003 01:58
		Re: Does this make sense? (scalar objects) By: marc schellens[1] on Fri, 05 December 2003 01:52
		Re: Does this make sense? (scalar objects) By: JD Smith on Wed, 03 December 2003 14:25
		Re: Does this make sense? (scalar objects) By: marc schellens[1] on Tue, 09 December 2003 07:59
		Re: Does this make sense? (scalar objects) By: JD Smith on Tue, 09 December 2003 11:16

Previous Topic:	Re: Error when running ICONTOUR
Next Topic:	Re: ActiveContours

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Wed Oct 08 13:52:10 PDT 2025

Total time taken to generate the page: 0.02341 seconds