· Mar 22

Comparing Two Lists/ Variables

Is there a way to compare the content of two variables/ lists and if they share a common element/ value return 1?

Example the two below both have "Yellow":

Set y = "Red, Green, Orange, Yellow"

Set x = "Purple, Black, Yellow, Pink"


The lists I am working with have over 30 elements/values that vary so it is difficult to hard code it to say look for "Yellow". 

Product version: IRIS 2022.1
Discussion (12)3
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If you want to treat them as lists, you probably want to use $LISTFROMSTRING along with $LISTGET, $LISTFIND, and $LISTLENGTH. All of which can be abbreviated to their initials, by the way - $LFS, $LG, $LF, $LL.

set y = $LFS("Red,Green,Orange,Yellow")
set x = $LFS("Purple,Black,Yellow,Pink")
for i=1:1:$LL(x){
    if $LF(y,$LG(x,i)) > 0 { 
        write $LG(x,i)_" found in both lists!",!
        //Or whatever else you want to do when you find a match here . . .

You can edit (or enhance) the above code to give you all matching elements. Below I share a code with you where you can choose the result data type (%List or %String) and the result scope (all the matching elements or just the first match).

/// Find common items of two lists or in two delimited strings
/// (as used in a $piece-function)
/// itm1: first list (as %List or comma-delimited %String)
/// itm2: other list (as %List or comma-delimited %String)
/// ans : 0 = return a comma-delimited %String with the first match found
///       1 = return a comma-delimited %String with all matches found
///       2 = return a %List with the first match found
///       3 = return a %List with all matches found
/// return value: according to <ans> argument
/// Hint: the "$d(var)," part is only needed if the <itm1> argument is
///       of %List type and can contain an "undefined" element like the
///       second element in $lb(11,,33).
ClassMethod FindCommonItems(itm1, itm2, ans = 0)
    set ptr=0, res="", all=ans#2
    set:'$lv(itm1) itm1=$lfs(itm1) set:'$lv(itm2) itm2=$lfs(itm2)
    while $listnext(itm1,ptr,val) { if $d(val),$lf(itm2,val) { set res=res_$lb(val) quit:'all } }
    quit $s(ans<2:$lts(res), 1:res)

I haven't put a massive amount of thought into this so it might be garbage for time/space complexity....

Set y = "Red, Green, Orange, Yellow"
Set x = "Purple, Black, Yellow, Pink"
set x=$ZSTRIP(x,"*W")
set y=$ZSTRIP(y,"*W")
k ^||members
for i=1:1:$L(x,","){
    set ^||Members($P(x,",",i),1)=""

for j=1:1:$L(y,","){
    set ^||Members($P(y,",",j),2)=""

//Now do a quick traverse of our members
set key=""
set both=""
for   {
    set key=$O(^||Members(key))
    set key2=""
    set key2=$O(^||Members(key,key2))
    if ($O(^||Members(key,key2))'="" set both=both_key_","

w !,"These records are in both lists "_both