[REBOL] Re: Array access and paths
From: joel:neely:fedex at: 18-May-2001 12:44
Hi, Gisle,
Gisle Dankel wrote:
> I think there are a few problems with paths...
>
> Here is an example:
>
> list: [A 0 B 5 C 0 D 0]
>
...
> >> idx: 'B
> == B
> >> list/:idx
> == 5
>
Another land mine not to step on if you take that last approach
is this: the type of the value in IDX actually makes a difference
in what the / means. If, as in your example, IDX is set to a word,
then
list/:idx
is (almost) equivalent to
select list idx
but if IDX is set to an integer, then
list/:idx
is equivalent to
pick list idx
instead. (This also means that using integers as "symbolic keys"
is problematic -- a pain in the neck.)
I said "(almost) equivalent" above because of this situation
>> idx: 'E
== E
>> list/:idx
** Script Error: Invalid path value: E
** Where: halt-view
** Near: list/:idx
>> select list idx
== none
in which throwing an error and returning NONE are *not* IMHO
equivalent behavior.
-jn-
