Web Interface for CASS

Analysis of dependencies on all non-deterministic operations

This analysis is useful if some operation has a non-deterministic behavior and one wants to find the reason for this behavior.

For this purpose, the analysis computes for each operation the set of operations with a non-deterministic definition that might be called by this operation. An operation has a non-deterministic definition if its definition contains overlapping left-hand sides or free variables. If the non-determinism of an operation is encapsulated by a set function or an encapsulated search operation of the module AllSolutions, it is considered as deterministic.

For instance, consider the operations

last xs | _ ++ [x] == xs = x where x free

coin = 0 ? 1

lastCoin = id (last [coin])

Then the operation lastCoin depends on the non-deterministic operations last and coin. Now consider the operations

f x = x ? lastCoin
g x = f x

Then the operation g depends on the non-deterministic operation f, and also on the non-deterministic operations last and coin.

In the long analysis output (produced by CASS in batch mode), the non-deterministic operations are shown together with the sequence of operations (limited to a length of 10) which calls the non-deterministic operation.