try/finally

[Andrew Janke]

Hi, Octave maintainers,

What do you think of adding a "finally" clause to the "try" block syntax?

Using unwind_protect in conjunction with try/catch is somewhat cumbersome:

unwind_protect
    try
        % ... main code ...
    catch
        % ... error handling ...
    end_try_catch
unwind_protect_cleanup
    % ... unconditional cleanup ...
end_unwind_protect

A try/catch/finally would have exactly the same semantics as the above, 
but would be more concise (just syntactic sugar):

try
  % ... main code ...
catch
  % ... error handling ...
finally
   % ... unconditional cleanup ...
end_try_catch

That seems like cleaner code to me.

It might be easier for new users to learn, too: "unwind protect" is a 
technical, computer science-y term that might be intimidating to newer 
programmers. And many of the other languages that they already know – 
Java, C#, Python, R, Julia, Maple, JavaScript, Ruby – all use "finally". 
"unwind-protect" seems to be a Lisp-ism, and I don't think we have many 
Lisp coders coming to Octave.

Matlab has neither try/catch nor unwind_protect, so compatibility is not 
an immediate concern. And I think they're more likely to add a finally 
than an unwind_protect.

Cheers,
Andrew