proper subgoal addressing via SUBGOAL/CSUBGOAL -- assuming these tactics did not handle Subscript in any special way;
tuned;
(* Title: HOL/Library/Quotient_Syntax.thy
Author: Cezary Kaliszyk and Christian Urban
*)
header {* Pretty syntax for Quotient operations *}
theory Quotient_Syntax
imports Main
begin
notation
rel_conj (infixr "OOO" 75) and
map_fun (infixr "--->" 55) and
fun_rel (infixr "===>" 55)
end