Error Handling

• Errors
• Throwing errors manually
• Catching errors with catch function

Errors

Errors occurring in some expressions are propagated to upper ones and force whole programs to crash. They can be caused in different ways, such as adding non-number values, joining a string and a list, and passing a wrong number of arguments to a function.

(print (+ 1 true)) ; Adding non-number values is invalid.

Throwing errors manually

The built-in error function creates an error with its name and message. It can be used to create and throw custom errors.

(error "MyError" "me ate sugar")

Catching errors with catch function

Because it is sometimes necessary to catch errors and perform retries or some cleanups, Cloe has a primitive function named catch which cancels error propagations and returns information of the errors as dictionaries.

; Prints '{"name" "ValueError" "message" "\"true\" is not a number"}'.
(print (catch (+ 1 true)))