public static Stella_Object convertToPrefixPropositionTree(Stella_Object tree) {
    if (Stella_Object.safePrimaryType(tree) == Logic.SGT_STELLA_CONS) {
      { Cons tree000 = ((Cons)(tree));

        { Symbol operator = ((Symbol)(tree000.value));

          if (Logic.kifQuantifierSymbolP(operator)) {
            tree000 = Logic.infixToPrefixQuantificationTree(tree000);
          }
          else {
            { ConsIterator it = tree000.rest.allocateIterator();

              while (it.nextP()) {
                if (Stella_Object.consP(it.value)) {
                  it.valueSetter(Logic.convertToPrefixPropositionTree(it.value));
                }
              }
            }
          }
          return (tree000);
        }
      }
    }
    else {
      return (tree);
    }
  }