Robert Cemper · Feb 16, 2021 2m read

FOREACH for ObjectScript

As you know ObjectScript has no FOREACH system command nor system function.
But it has a wide room for creativity.

The task is to loop over a global or local array and do something FOR EACH element.

There are 2 possible solutions:
- creating a macro that generates the required code sequences
- creating an Extended Command to perform the action.

Both ways are presented here.
The macro is a generic and quite flexible solution and easy to adapt if required.

##;FOREACHMACRO ; macro definitions
##; %key = variable provide to loop trough array
##; %arr = the gobal or local array to be looped on
##; %the method or routine to be executed for each node.
##; $$$foreach = forward loop $$$foreeachR = reverse loop
#define foreach(%key,%arr,%do) set %key="" for  set %key=$o(%arr(%key)) q:%key=""  do %do
#define foreachR(%key,%arr,%do) set %key="" for  set %key=$o(%arr(%key),-1) q:%key=""  do %do

You simply include the macro and apply it.

test $$$foreach(key,^rcc,show)
show zwrite @$zr,! quit

Creating a command extension is available for all namespaces.

It needs to be included in %ZLANGC00.mac  by #include ZZFOREACH  
the related code is here:

##; run $order() ascending or descending on global or local arrays 
##; pass semicolon separated parameter string ("%array;%do;%fwd,;%key")
##; %array = global or local variable name
##; %do = routine or method to be executed for each run
##; %fwd = 1/-1 loop direction ascending / descending, default = 1
##; %key = first key if existing
ZZFOREACH(%par) public {
   set %par=$lfs(%par,";")
   new %array,%do,%fwd,%key,%val
   set %array=$lg(%par,1),%do=$lg(%par,2),%fwd=$lg(%par,3),%key=$lg(%par,4)
   if '%fwd set %fwd=1
   if %key]"" set %key=$o(@%array@(%key),$s(%fwd<1:-1,1:1))
   for  set %key=$o(@%array@(%key),%fwd,%val) quit:%key=""  do @%do
   quit 1 

In addition to the macro, the command allows optionally  to run zzFOREACH from a provided starting point forward or backward

DEMO>zzforeach "^rcc;show^dump(%array,%key,%val)"
^rcc(1) = 1
^rcc(2) = 2
^rcc(3) = 3
^rcc(4) = 4
^rcc(5) = 5

or from subscript 3:

DEMO>zzforeach "^rcc;show^dump(%array,%key,%val);;3"
^rcc(3) = 3
^rcc(4) = 4
^rcc(5) = 5

or the same reverse:

DEMO>zzforeach "^rcc;show^dump(%array,%key,%val);-1;3"
^rcc(3) = 3
^rcc(2) = 2
^rcc(1) = 1

The INC files are available on OEX with ZPM

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Discussion (6)1
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This is something I've asked for a very long time, every modern language has some kind of implementation.
Globals ($Query like), local arrays, ListOf/ArrayOf,%List are all candidates.
It seems that COS hasn't much of attention the last couple of years

You hit the spot: Every modern language !  

There's nothing that holds ISC back in modernizing COS wink