!7

abstract sclass Proposal { toString { ret sfu(this); } }

static noToString record EnclosedIn(S l, LS contents, S r) extends Proposal {}
static noToString record Infix(LS l, S op, LS r) extends Proposal {}

svoid parse(LS tok) {
  // drop first and last
  if (l(tok) >= 3)
    emit(new EnclosedIn(first(tok), dropFirstAndLast_noNewList(tok), last(tok)));
  for (int i = 1; i < l(tok)-1; i++)
    emit(new Infix(subList(tok, 0, i), tok.get(i), subList(tok, i+1)));
}

p-exp {
  LS tok = javaTokC("[(a|b), (c|d), (e|f)]");
  parse(tok);
}