In some scenarios, when there is an error and there is a risk of the software producing an incorrect value or failing entirely, we might be able to replace the result with another, safer value. We call this value substitution, since we are in fact replacing the actual erroneous result for a value that is to be considered non-disruptive (it could be a default, a well-known constant, a sentinel value, or simply something that does not affect the result at all, like returning zero in a case where the result is intended to be applied to a sum).
Value substitution is not always possible, however. This strategy has to be carefully chosen for cases where the substituted value is actually a safe option. Making this decision is ...
