Docmosis may report “Invalid operand for unary operator” when a unary minus is applied directly to a data field.
For example:
<<{(-b + sqrt($d)) / (2*a)}>>
The problem is the "-b".
The solution is to rewrite the "negative sign" as an expression that uses the subtraction operation and two operands:
<<{(0-b + sqrt($d)) / (2*a)}>>
In this case, "0-b" is the same as "negative b" or "-b".
Or, where appropriate, rearrange the expression:
<<{(sqrt($d)-b) / (2*a)}>>
This does not mean that b cannot contain a negative value in your JSON data. A value such as "b": -3 is valid. The issue is specifically the use of the unary - operator directly on the field within the template expression.
