Re: [Caml-list] Proposal: extend try to handle success

[Gabriel Scherer <gabriel.scherer@gmail.com>]

This proposal lifts my only (and surprisingly blocking) reservation
with "let-try", namely the fact that I have no idea which of "let-try
<decl> in <expr> with <handler>" or "let-try <decl> with <handler> in
<expr>" is the right syntax in the general case. With this proposal,
value-return-handlers and exception-handlers can be ordered at will by
the user.

(Thank you for mentioning the relation to the effect-handler work. I
distinctly remember having the realization that this syntax would
solve our problem in a discussion with you, Sam Lindley and Ohad
Kammar after their HOPE talk in Copenhagen. Could this research
improve OCaml as a... side-effect?)


On Tue, Feb 4, 2014 at 7:09 PM, Jeremy Yallop <yallop@gmail.com> wrote:
> On 4 February 2014 17:14, Simon Cruanes <simon.cruanes.2007@m4x.org> wrote:
>> Le Tue, 04 Feb 2014, Jeremy Yallop a écrit :
>>> I'd like to propose extending OCaml with a design once suggested by
>>> Christophe Raffalli which elegantly handles this case.  The details,
>>> along with an implementation that you can try out, are in the
>>> following blog post:
>>>
>>>     http://ocamllabs.github.io/compiler-hacking/2014/02/04/handler-case.html
>>>
>>> Feedback welcome!
>>
>> This is very nice and detailed, but I'm not sure to follow how this is
>> supposed to help in some cases you mention. Namely, the
>>
>> match (try Some (foo) with End_of_foo -> None) with
>>     | Some x -> a
>>     | None -> b
>>
>> transformation is used to preserve tail-call. Would the new
>>
>> try foo with
>>     | End_of_foo -> b
>>     | val x -> a
>>
>> present the same behavior w.r.t tail-call?
>
> Yes, 'a' is in tail position in both snippets.
>
>> If the answer is yes, then I find it very interesting :)
>
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