Octave supports a limited form of exception handling modeled after the unwind-protect form of Lisp.
The general form of an unwind_protect block looks like this:
unwind_protect body unwind_protect_cleanup cleanup end_unwind_protect
where body and cleanup are both optional and may contain any Octave expressions or commands. The statements in cleanup are guaranteed to be executed regardless of how control exits body.
This is useful to protect temporary changes to global variables from
possible errors. For example, the following code will always restore
the original value of the global variable frobnosticate
even if an error occurs in the first part of the unwind_protect
block.
save_frobnosticate = frobnosticate; unwind_protect frobnosticate = true; ... unwind_protect_cleanup frobnosticate = save_frobnosticate; end_unwind_protect
Without unwind_protect, the value of frobnosticate
would not be restored if an error occurs while evaluating the first part
of the unwind_protect block because evaluation would stop at the
point of the error and the statement to restore the value would not be
executed.
In addition to unwind_protect, Octave supports another form of
exception handling, the try block.