The mode analyser is a variant of the ECLiPSe that inserts instrumentation into the clause definitions of predicates (defined in the named file) during compilation in order to record mode usage of each predicate argument. The code is then run as many times as is necessary to capture the most common invocations of each predicate undergoing analysis. Finally, the results are analysed, using mode_analyser:result/0, to produce suggested mode/1 directives for each predicate.
The mode/1 directive informs the compiler that the arguments of the specified predicate will always have the corresponding form when the predicate is called. The compiler utilises this information during compilation of the predicate in order to generate more compact and/or faster code. Specifying the mode of a predicate that has already been compiled has no effect, unless it is recompiled. If the specified procedure does not exist, a local undefined procedure is created.
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 1]: mode_analyser:analyse('queens_gfc.pl'). queens_gfc.pl compiled traceable 13920 bytes in 0.10 seconds Yes (0.10s cpu)