Re: [TCLCORE] TIP#329: Try/Catch/Finally syntax

[Joe E. <jen...@fl...>]

Andreas Leitgeb wrote:
> Twylite wrote:
> > The counterpoints have already been presented.  I think there are strong
> > arguments both ways,
>
> I'm definitely biased, but the only argument for handler-specific
> variables, that I found in the discussion was that all the other
> languages (especially Java) have per-handler variables.
>
> That one isn't strong in my mind.  Did I miss other arguments?

Specific example:

	try {
	    open $filename r
	} on ok {fp} {
	    # ...
	} on error {msg opts} {
	    # ...
	}

(Which was one of the motivating use cases for dispatching
based on return code in the first place.)

With try/as, this would be:

	try {
	    open $filename r
	} as {xxx opts} on ok {
	    # (1) here $xxx is a file channel.
	} on error {
	    # (2) here $xxx is an error message.
	}
	# (3)

For the sake of clarity, I'd want to use different variable
names in the two handler clauses -- "fp" for the case where
the result is a file channel, "msg" for the case where it's
an error message.  (I can't think of a good variable name to
use in the "as" clause.)

At point (3), you know that $xxx and $opts are set to _something_,
but you don't know what.  You usually don't care, either.


--Joe English

  jen...@fl...