The purpose of this module is to find which part of the program has been used by a certain goal. Usage is defined in terms of clauses that have fired, seperated in clauses that succeeded at least once and clauses that failed on each occasion.
This module relies on the SWI-Prolog tracer hooks. It modifies these hooks and collects the results, after which it restores the debugging environment. This has some limitations:
- The performance degrades significantly (about 10 times)
- It is not possible to use the debugger during coverage analysis
- The cover analysis tool is currently not thread-safe.
The result is represented as a list of clause-references. As the references to clauses of dynamic predicates cannot be guaranteed, these are omitted from the result.