%SYSFUNC() wrapped concatenation functions give an error while encountering parentheses - function

Question

I need to write a macro program to generate a list for moving average calculation where I will need some lines to be constructed like this:
var1_ma_past_1=mean(var1, lag1(var1), lag2(var1), lag3(var1), lag4(var1), lag5(var1));
var1_ma_past_2=mean(lag1(var1), lag2(var1), lag3(var1), lag4(var1), lag5(var1), lag6(var1));
var1_ma_past_3=mean(lag2(var1), lag3(var1), lag4(var1), lag5(var1), lag6(var1), lag7(var1));
[...]
var2_ma_past_1=mean(var2, lag1(var2), lag2(var2), lag3(var2), lag4(var2), lag5(var2));
my sample program is
%macro test ;
%do i = 1 %to 5;
%let ln&i = ;
%do j = 1 %to 5;
%let dml = %str(,);
%let pos = %str(lag&i(var&j));
%let ln&j = %sysfunc(catx(&dml, &&ln&j, &pos));
%end;
%end;
/* example output */
%put &ln1;
%mend test;
%test
&j start and end values are planned to be replaced with parameters though.
the output is desired for &ln1
lag1(var1),lag2(var1),lag3(var1),lag4(var1),lag5(var1)
but for &ln2 &ln3 etc it's not (lag1(varn) is missing)
lag2(var4),lag3(var4),lag4(var4),lag5(var4)
lag2(var3),lag3(var3),lag4(var3),lag5(var3)
Besides, I got flooding log output saying ERROR: Required operator not found in expression: which is because of the parentheses inside of cats(), which is inside of %sysfunc(), an example macro to replicate this is
%macro test2;
%let x=meow;
%put %sysfunc(cats(x,lag()));
%mend;
%test2
I tried to mask the parentheses with %str, %superq, %bquote but none worked.
I'd like to learn
the reason for incorrect output for &ln2, &ln3 and so on
the reason for ERROR: Required operator not found in expression: and how to fix it (or a workaround, or even to suppress the error if it's not critical)
Thanks in advance.

Answer 1

There is no need to use CAT...() functions in macro code.
In macro code to concatenate values you just expand them next to each other.
Also it looks like your logic is mixing up the I and J counters.
%macro test ;
%do i = 1 %to 5;
%let list = ;
%let dlm = ;
%do j = 1 %to 5;
%let list = &list.&dlm.lag&j(var&i) ;
%let dlm = ,;
%end;
%put &=i &=list;
%end;
%mend test;
%test
Results:
I=1 LIST=lag1(var1),lag2(var1),lag3(var1),lag4(var1),lag5(var1)
I=2 LIST=lag1(var2),lag2(var2),lag3(var2),lag4(var2),lag5(var2)
I=3 LIST=lag1(var3),lag2(var3),lag3(var3),lag4(var3),lag5(var3)
I=4 LIST=lag1(var4),lag2(var4),lag3(var4),lag4(var4),lag5(var4)
I=5 LIST=lag1(var5),lag2(var5),lag3(var5),lag4(var5),lag5(var5)
For your actual problem you might want to create a macro that only returns the comma delimited list as the result of the macro call.
%macro lags(varname,first,last);
%local lag dlm;
%do lag= &first %to &last ;
%if (&lag > 0) %then %*;&dlm.lag&lag(&varname);
%else %*;&dlm.&varname;
%let dlm=,;
%end;
%mend lags;
%put var1_ma_past_1=mean(%lags(var1,0,5));
%put var1_ma_past_2=mean(%lags(var1,1,6));
%put var1_ma_past_3=mean(%lags(var1,2,7));
%put var2_ma_past_1=mean(%lags(var2,0,5));
Why you are getting those error messages:
The %sysfunc() macro function needs to try to figure out whether each argument is character or numeric for a function like CATX() that can operate on either type of input. That is why the () in the argument values is confusing it since it looks like you are trying to pass a numeric expression.
18 %put %sysfunc(catx(|,a(b),b));
ERROR: Required operator not found in expression: a(b)
a(b)|B
19 %put %sysfunc(catx(|,(1+2),b));
3|B
You could force in quotes around the values and then remove them later (if your values don't actually contain quotes).
%let left=A(b);
%let right=b;
%let intermediate=%sysfunc(catx(|,"&left","&right"));
%let want=%sysfunc(compress(&intermediate,%str(%"));
%put &=want;