ERRORS

Error Type

The error type consists of an identifying keyword and a data/payload value. This value is typically a string but can be any valid value.

(type [error]) returns :Error The form (car [error]) returns the keyword identifying this error. The form (cdr [error]) returns the data value for the error. Note the use of car/cdr to pull apart an error even though it is not of the pair type. Use (mk-err :[ID] value) to create an error type or (err :[ID] value) to "raise" an error (see below).

Raising an error

Runtime errors will be "raised". This means the program execution will halt and the debugger will be entered. Currently this only allows examining the running state but will eventually include the ability to modify state and restart as other Lisps allow. Code can raise an error with the err form, for instance (err :some-error-type "This is my error") will raise an error and interrupt the program.

Note, the (get-error FORM+) form can be used to programmatically return a raised error instead of breaking to the debugger.

Returning an error

Code can return an error instead of breaking into the debugger. Use the (mk-err :[ERROR ID] vallue) to create an error and then use it as any other value (return it from a function for instance). This may be appropriate for a common error that does not warrent breaking to the debugger.

References

See the docs string for:

• err
• mk-err
• err?
• ok?
• get-error