TALES boolean coercion

At times, TALES needs to interpret the result of an expression as a boolean (true/false) value. If the expression result is not already a System.Boolean then TALES will perform automatic type coercion, according to the following rules:

1. A null reference is false
2. Non-null instances of nullable reference types are true
3. Instances of non-nullable value types are true if they are not equal to default(T) for their type. Otherwise they are false

Beware that the not: expression prefix has its own rules for interpreting values as a boolean.