5.9.5 Other Conditions

The following conditions are for prescribing or checking the breakpoint type. They cause an exception if used outside the debugger or in execution_state/2.

advice

The breakpoint in question is of advice type.

debugger

The breakpoint in question is of debugger type.

The following construct converts an arbitrary Prolog goal into a condition.

true(Cond)

The Prolog goal Cond is true, i.e. once(Cond) is executed and the condition is satisfied if and only if this completes successfully. If an exception is raised during execution, then an error message is printed and the condition fails.

The substitutions done on executing Cond are carried out. Cond is subject to module name expansion. If used in the test part of spypoint conditions, then the goal should not have any side effects, as the test part may be evaluated several times.

The following conditions represent the Boolean constants.

true

[]

A condition that is always true. Useful e.g. in conditionals.

false

A condition that is always false.