class BurrowsWheelerTransform{
   fcn init(chr="$"){ var special=chr; }
   fcn encode(str){
      _assert_(not str.holds(special), "String cannot contain char \"%s\"".fmt(special) );
      str=str.append(special);
      str.len().pump(List().merge,'wrap(n){ String(str[n,*],str[0,n]) })
      .pump(String,T("get",-1));    // last char of each "permutation"
   }
   fcn decode(str){
      table:=List.createLong(str.len(),""); // ("",""..), mutable
      do(str.len()){
     foreach n in (str.len()){ table[n]=str[n] + table[n] }
     table.sort();
      }   // --> ("$dogwood","d$dogwoo","dogwood$",...)
      table.filter1("%s*".fmt(special).glob)[1,*];  // str[0]==$, often first element
   }
}