The following script is expected to say letter a but it says a to g one by one. Any comments? GrADS version v1.8SL9. str='abcdefg' rec=math_strlen(str) i=1 while(i<=rec) ss=substr(str,i,1) if(ss = 'a') then * What is wrong here? say ss endif i=i+1 endwhile ga-> run teststr.gs a b c d e f g