Picat Picat Exception Handling and Debugging

Question 1

Which construct catches exceptions in Picat?

Accepted Answer

catch(Goal, Error, Handler)

Answer

`catch(Goal, Error, Handler)` executes Goal and runs Handler if a matching exception is raised.

Question 2

How do you raise an exception in Picat?

Accepted Answer

throw(Error)

Answer

`throw(Error)` raises an exception carrying the given error term in Picat.

Question 3

What is the standard ISO format for a type error term in Picat?

Accepted Answer

error(type_error(Type, Value), _)

Answer

ISO standard errors in Picat use `error(type_error(Type, Culprit), Context)` as the thrown term.

Question 4

Which error type is thrown when a predicate requires an instantiated argument but receives a variable?

Accepted Answer

instantiation_error

Answer

`instantiation_error` is thrown when a predicate receives an insufficiently instantiated (unbound) argument.

Question 5

What happens if no `catch` clause matches a thrown exception in Picat?

Accepted Answer

The exception propagates up the call stack

Answer

An unmatched exception continues propagating up the call stack until a matching catch or the top level is reached.

Picat Practice Test