Generates all combinations of the indices of n objects taken k at a time in lexicographic order.
Category:  Combinatorial 
is a numeric constant, variable, or expression that specifies the total number of objects.
is a numeric constant, variable, or expression that specifies the number of objects in each combination.
is a numeric variable that contains indices of the objects in the combination that is returned. Indices are integers between 1 and n, inclusive.
Tip  If index1 is missing
or zero, then the CALL LEXCOMBI routine initializes the indices to index1=1 through indexk=k . Otherwise, CALL LEXCOMBI creates a new combination by removing
one index from the combination and adding another index.

data _null_; array x[5] $3 ('ant' 'bee' 'cat' 'dog' 'ewe'); array c[3] $3; array i[3]; n=dim(x); k=dim(i); i[1]=0; ncomb=comb(n,k); do j=1 to ncomb; call lexcombi(n, k, of i[*]); do h=1 to k; c[h]=x[i[h]]; end; put @4 j= @10 'i= ' i[*] +3 'c= ' c[*]; end; run;
j=1 i= 1 2 3 c= ant bee cat j=2 i= 1 2 4 c= ant bee dog j=3 i= 1 2 5 c= ant bee ewe j=4 i= 1 3 4 c= ant cat dog j=5 i= 1 3 5 c= ant cat ewe j=6 i= 1 4 5 c= ant dog ewe j=7 i= 2 3 4 c= bee cat dog j=8 i= 2 3 5 c= bee cat ewe j=9 i= 2 4 5 c= bee dog ewe j=10 i= 3 4 5 c= cat dog ewe
%macro test; %let x1=0; %let x2=0; %let x3=0; %let n=5; %let k=3; %let ncomb=%sysfunc(comb(&n,&k)); %do j=1 %to &ncomb+1; %syscall lexcombi(n,k,x1,x2,x3); %let jfmt=%qsysfunc(putn(&j,5.)); %let pad=%qsysfunc(repeat(%str(),6%length(&x1 &x2 &x3))); %put &jfmt: &x1 &x2 &x3 &pad sysinfo=&sysinfo; %end; %mend; %test