Array union syntax: grumble or bug?

[Jim Ault]

[full text of the original email appears below]

Start with
"Rev only uses associative arrays"
 thus you need to get the key list for access.
There is a feature request to add "indexed" access, which would allow
dataArr[0]  dataArr[1] etc

Second
"Rev allows variables without 'variable typing' or 'casting'
thus accessing a 'base array' is accessing an empty key list, which would
mean the variable "dataArr" is not really an array yet.

This also allows the operation:
put "sunny day" into dataArr["weather"]
put "78 degrees" into dataArr["temperature"]
put keys(dataArr) into msg
put "any old string" into dataArr
--datArr is no longer an array
put keys(dataArr) into msg --> empty


Third
"Rev finds an empty key list, and does not do a comparison to add keys from
the new array ( since an empty array is not technically an array yet, just a
variable )"
thus 
put newArr into dataArr  --would be the operation, as you have shown

This is one of the ways "non-type-casting variable" handling means different
programming conventions.

To answer your two questions:
>  1) union with an empty base array always result in empty instead of adding
> the new array
because the 'keys of this variable' are empty
>  2) an array is "empty" even if it is not (null) and has stuff in it (same
> with other binary data)
because the 'keys of this variable' are NOT empty, and you need to use the
list of keys to access the data.

Hope this helps

Jim Ault
Las Vegas



On 10/7/07 5:07 AM, "David Bovill" <david at openpartnership.net> wrote:

> This one has bothered me for a while now - is there a good reason for these
> two rather strange behaviors of the "union" command for arrays:
> 
>  1) union with an empty base array always result in empty instead of adding
> the new array
>  2) an array is "empty" even if it is not (null) and has stuff in it (same
> with other binary data)
> 
> So AFAIK to add an array in a repeat loop to an initially empty array you
> need to use an awkward and slow handler like the one below:
> 
> on array_Add someArray, @toArray
>     -- why cant we just test if array is empty?
>     if keys(toArray) is empty then
>         -- why does "union" with an empty base array always result in empty?
>         put someArray into toArray
>     else
>         union toArray with someArray
>     end if
> end array_Add