Re: when to use "copy" vs "set" [was Re: Manipulating text]
Re: when to use "copy" vs "set" [was Re: Manipulating text]
- Subject: Re: when to use "copy" vs "set" [was Re: Manipulating text]
- From: has <email@hidden>
- Date: Sat, 26 Sep 2009 17:10:40 +0100
Jon Pugh wrote:
>In other words, when do you use "copy" and when "set"
It'a not painfully obvious, in fact it's downright obtuse and has
confused people since the dawn of AppleScript.
The flaw in the design of AS's 'copy' command is that it muddles two
completely unrelated actions - assignment and cloning - that should
have been addressed separately. This just makes it harder for users to
understand what it's doing, and why. The correct approach would be to
use 'set' for _all_ assignments, and provide a separate 'a copy of'
operator for cloning AS objects, e.g.:
set new_list to a copy of old_list
The rest is just a matter of teaching users the difference between
mutable and immutable objects. Which shouldn't be all that difficult,
since AS users are already well used to dealing with mutable objects
whenever they script applications. Unfortunately, the old ASLG rather
went off the rails on that topic, with a bunch of vague waffle about
'data sharing', which really didn't help either.
I suppose there's also the question of how you explain variables,
which in AppleScript are simply labels that you attach to in-memory
objects so that you can identify those objects again later. Though I
will admit to using the more common (if less accurate) 'a variable is
a container you put objects in' metaphor myself when explaining this
stuff to novices. I've never been quite sure what the best balance
between correctness, ease of understanding, and common public usage is
on this one.
Ah well; who ever said designing a language was easy...?
Regards,
has
--
Control AppleScriptable applications from Python, Ruby and ObjC:
http://appscript.sourceforge.net
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