KB43944: Derived metric based on an attribute form defined as Text returns blank results in MicroStrategy 9.x and 10.x

SYMPTOM:
 
A derived metric based on an attribute form defined as Text returns blank results in Strategy 9.x and 10.x.
 
STEPS TO REPRODUCE
 
These are the steps to reproduce the issue in Strategy Tutorial:
Max(){Category} -1
 

1. Create a new report.
2. Add Category attribute to the grid template.
3. Create a derived metric with the following definition:
4. Run the report: no data will be displayed for the derived metric created in Step 3.

This issue does not occur when using a non-text attribute form.
 
CAUSE:
 
This is working by design, arithmetic operations on string types are not supported.