From: ES <ruby-ml@...>
Date: 2005-03-03T13:51:10+09:00
Subject: Re: Continuation example

On Thu, March 3, 2005 12:02 am, Jos Backus said:
> On Wed, Mar 02, 2005 at 03:18:01PM +0900, ES wrote:
>> On Wed, March 2, 2005 12:04 am, Jos Backus said:
> [snip]
>> It'd be great fun if exception handling could *literally* be described
>> parallel to the method :)
>
> I'm still trying to wrap my head around this. It sounds like you want a
> special kind of method attribute that is itself a method that is invoked under
> certain circumstances?

Oh, no, more of a concrete separation of exception handling from the method
body: conceptually think IDE-level[1]. You specify the correct code path in
your method (i.e. write it like nothing could ever go wrong), then double-click
on the method name and it brings up a little window where you can enter all
of the exception handling code[2]. Obviously this in particular is more a
convenience/clutterlessness enhancement, but it might help in redirecting
exception processing back to 'handling' instead of 'reporting'.

[1] IDE used just for visualization of example, no reason this couldn't
    be used at any level from language specification up.
[2] Exception handling, says I, should exist as a meta-level in a given
    program without the access restraints placed on normal code.

So here,

  This is the method              This is the error handling, tab-separated :)
          |                                   |
          V                                   V
>> <pre>
>>
>> def foo()                      handler
>>   # Do something
>>   do_something()               fail? do fix_do_something(); retry :once; end
>>
>>   # Other ops
>>   if something_else
>>     do_something_else()        fail? do fix_do_something_else(); retry 2;
>> end
>>   end
>> end                            end
>>
>> </pre>
>>
>> Good work.
>
> Thanks.
>
> Two nits I found after sending:
>
>> > # a list element is divisible by 3, if which case it is considered "bad".
>                                         in
>> >   def each(check)
>> >     cc = nil                <-- not needed
>> >     @arr.each do |elem|
>
> Jos Backus

E