*process source xref attributes or(!);
 /*--------------------------------------------------------------------
 * 08.08.2014 Walter Pachl  translated from REXX version 1
 *-------------------------------------------------------------------*/
 ent: Proc Options(main);
 Dcl (index,length,log2,substr) Builtin;
 Dcl sysprint Print;
 Dcl occ(100) Bin fixed(31) Init((100)0);
 Dcl (n,cn,ci,i,pos) Bin fixed(31) Init(0);
 Dcl chars Char(100) Var Init('');
 Dcl s Char(100) Var Init('1223334444');
 Dcl c Char(1);
 Dcl (occf,p(100)) Dec Float(18);
 Dcl e Dec Float(18) Init(0);
 Do i=1 To length(s);
   c=substr(s,i,1);
   pos=index(chars,c);
   If pos=0 Then Do;
     pos=length(chars)+1;
     cn+=1;
     chars=chars!!c;
     End;
   occ(pos)+=1;
   n+=1;
   End;
  do ci=1 To cn;
    occf=occ(ci);
    p(ci)=occf/n;
    End;
  Do ci=1 To cn;
    e=e+p(ci)*log2(p(ci));
    End;
  Put Edit('s='''!!s!!''' Entropy=',-e)(Skip,a,f(15,12));
  End;