This predicate displays the suggested invocation modes for each predicate compiled using the mode analyser into the calling context module. The suggested mode annotations can be passed to the mode/1 directive for the associated predicate. The predicate is a tool and as such can be invoked for an arbitrary module using mode_analyser:result@Module.
The possible argument modes produced for each argument of each predicate are:
+ The argument is instantiated, i.e. it is not a variable.
++ The argument is ground.
- The argument is not instantiated, it must be a free variable without
any constraints, especially it must not occur in any other argument
and it cannot be a suspending variable.
? The mode is not known or it is neither of the above ones.
NOTE: It is imperative to understand that the results of mode analysis are merely suggestions for the invocation modes of a predicate based on runtime information. If there are potential predicate invocation modes that were not exercised during runtime, the tool is unable to account for them in its analysis. For the mode specifier '-' the mode analyser does not determine whether the variable occurs in any other argument (i.e. is aliased), this must be manually verified. In summary, the programmer must verify that the suggested modes are correct before using the directive in the code. If the instantiation of the predicate call violates its mode declaration, no exception is raised and its behaviour is undefined.
[eclipse 2]: nqueens(8, Qs).
L = [1, 5, 8, 6, 3, 7, 2, 4]
Yes (0.00s cpu, solution 1, maybe more) ?
...
...
Yes (0.10s cpu)
[eclipse 5]: mode_analyser:result.
nqueens(++, -)
noattack(?, ?)
safe(+)
noattack(?, +, ++)
Yes (0.00s cpu)