Recover in Scheme

In Scheme, we don’t have a direct equivalent of Go’s panic and recover mechanism. However, we can simulate a similar behavior using Scheme’s exception handling system. Here’s how we might approach this:

(define (may-error)
  (error "a problem"))

(define (main)
  (call-with-current-continuation
   (lambda (exit)
     (with-exception-handler
      (lambda (condition)
        (display "Recovered. Error:\n")
        (display condition)
        (newline)
        (exit #f))
      (lambda ()
        (may-error)
        (display "After may-error()\n"))))))

(main)

In this Scheme code:

1. We define a function may-error that raises an error. This is similar to the mayPanic function in the original example.

2. The main function uses Scheme’s exception handling mechanism to catch and recover from errors:

   • call-with-current-continuation is used to create an exit point that we can use to stop execution after handling an error.

   • with-exception-handler is used to set up an exception handler. This is similar to the deferred function in the original example.

   • If an exception occurs, the handler will display the error message and then use the continuation to exit the function.

   • If no exception occurs, the code after may-error would be executed (but in this case, it won’t be reached).

3. We then call the main function to run our program.

When you run this program, you should see output similar to:

Recovered. Error:
a problem

This demonstrates how we can catch and recover from errors in Scheme, allowing our program to continue execution instead of crashing. While the mechanism is different from Go’s panic and recover, the end result is similar: we’re able to handle errors gracefully and prevent them from crashing our entire program.