From: Gennady Bystritsky <Gennady.Bystritsky@...>
Date: 2006-10-28T03:35:03+09:00
Subject: Re: can there be a "with" construction?

Jacob Fugal wrote:
> On 10/27/06, Gennady Bystritsky <Gennady.Bystritsky@quest.com> wrote:
>> matt neuburg wrote:
>>> Some languages have a "with" construction, where undefined methods
>>> are routed to a designated object. Here's an example from UserTalk:
>>> 
>>> with system.startup {
>>>    string(license)
>>> }
>>> 
>>> UserTalk knows what "string" is, but when it can't find "license" it
>>> reinterprets it as system.startup.license, which works. In
>>> UserTalk, you can even chain these tests:
>>> 
>>> with system.temp, system.startup {
>>>    string(license)
>>> }
>>> 
>>> That means we try system.temp.license and if that doesn't exist we
>>> proceed to system.startup.license.
>>> 
>>> So my question is: is Ruby amenable to this kind of construction? Is
>>> there a way to bend the language to that it acts like this? Thx - m.
>> 
>> Something like this?
>> 
>> def with(*objects)
>>   begin
>>     yield
>>   rescue NoMethodError => exception
>>     o = objects.detect { |_o|
>>       _o.respond_to? exception.name
>>     } or raise
>> 
>>     o.send exception.name, *exception.args
>>   end
>> end
> 
> It's a start, but:
> 
> 1) I don't think we really want to redispatch NoMethodErrors for
> messages that had an explicit receiver. Only the ones with implicit
> receivers. 
> 
> 2) it stops execution of the block after redispatching the
> first exception:
> 
>   with(Time) do
>     "aaa".now
>     puts "Never get here"
>   end # nothing printed
> 
> Jacob Fugal

Hmm... I must have misunderstood the OP. I somehow thought that in
"those" languages string(license) translates to calling method "license"
on "string", hence the solution. My bad, sorry.

Gennady.