private String getChoice(Token operator, boolean whenTrue) {
            if (whenTrue) {
                switch (operator.getID()) {
                case Token.EQ:
                    return "==";
                case Token.NE:
                    return "!=";
                case Token.LT:
                    return "<";
                case Token.GT:
                    return ">";
                case Token.LE:
                    return "<=";
                case Token.GE:
                    return ">=";
                }
            }
            else {
                switch (operator.getID()) {
                case Token.EQ:
                    return "!=";
                case Token.NE:
                    return "==";
                case Token.LT:
                    return ">=";
                case Token.GT:
                    return "<=";
                case Token.LE:
                    return ">";
                case Token.GE:
                    return "<";
                }
            }

            throw new RuntimeException("Unknown relational operator: " +
                                       operator.getImage());
        }