How can you handle exceptions and error handling in Prolog?

Prolog - Interview Questions

Exception handling and error handling in Prolog can be accomplished using the built-in predicate `catch/3`. The `catch/3` predicate allows you to catch and handle exceptions that occur during the execution of a goal. Here's how you can handle exceptions and errors in Prolog:

1. Syntax of `catch/3`:
The `catch/3` predicate has the following syntax:

   catch(Goal, Exception, Handler)â€‹

   * `Goal` is the goal you want to execute.
   * `Exception` is the exception that you want to catch.
   * `Handler` is the goal that will be executed if the specified exception is raised.

2. Catching Exceptions :
   * When `catch/3` is executed, it attempts to evaluate the `Goal`.
   * If no exception occurs, the `Goal` is executed normally, and the result is returned.
   * If an exception matching the specified `Exception` occurs during the execution of the `Goal`, the control is transferred to the `Handler`.
   * The `Handler` goal can handle the exception, perform error recovery, or take appropriate actions.

3. Handling Exceptions :
   * The `Handler` goal is executed in the context where the exception occurred.
   * It can examine the exception term and make decisions based on its content.
   * The `Handler` can throw another exception or perform error recovery, such as printing an error message, backtracking, or returning a default value.

Example usage:

divide(X, Y, Result) :-
    catch(Result is X / Y, error(Err, _), handle_error(Err, Result)).

handle_error(zero_divisor, Result) :-
    write('Error: Division by zero.'),
    Result = 'Infinity'.â€‹

In this example, the `divide/3` predicate attempts to calculate the division of `X` by `Y`. If a `zero_divisor` error occurs, the `handle_error/2` predicate is called, which displays an error message and assigns the result as `'Infinity'`.

By using `catch/3`, you can define specific exception handling behavior to handle errors, recover from exceptional conditions, and control the flow of execution when exceptions occur in Prolog programs.