@Override
        public final boolean equals(Object o) {
            if (o == null) return false;
            else if (this == o) return true;
            else if (!(o instanceof BinaryExpression)) return false;
            final BinaryExpression<?, ?, ?> that = (BinaryExpression<?, ?, ?>) o;
            return Objects.equals(firstInner, that.first()) &&
                Objects.equals(secondInner, that.second()) &&
                Objects.equals(operator(), that.operator());
        }
Abstract base for a minus operation.

@param <T>       the input type
@param <FIRST>   the first operand expression type
@param <SECOND>  the second operand expression type
runtime-parent/runtime-compute/src/main/java/com/speedment/runtime/compute/internal/expression/MinusUtil.java