Support for handling exceptional situations such as bad user input, implementation bugs, and input/output errors is provided by a set of words built using continuations.

Two words raise an error in the innermost error handler for the current dynamic extent:

throw ( error -- * )

rethrow ( error -- * )

Words for establishing an error handler:

cleanup ( try cleanup-always cleanup-error -- )

recover ( ..a try: ( ..a -- ..b ) recovery: ( ..a error -- ..b ) -- ..b )

ignore-errors ( ... quot: ( ... -- ... ) -- ... )

Syntax sugar for defining errors:

ERROR:

Unhandled errors are reported in the listener and can be debugged using various tools. See The debugger.
Restartable errors
The debugger
Post-mortem error inspection
Common error handling pitfalls

When Factor encounters a critical error, it calls the following word:

die ( -- )