Yes it is as you say   
      
   f(a)==(#a=0=>[[]];#a<4=>[[a.1]];[[a.1,a.2],[a.2,a.3]])   
      
   m:=f("1234")   
      
   generate f compiled as String ->List List Character   
   and not String -> Any   
   (and this make disappear the warning in "[concat(map(x+->x::String,m.j)) for j   
   in 1..#m]")   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)