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comp.lang.ruby

Rub 1.9: "inline rescue" doesn't work?

Iñaki Baz Castillo

3/1/2009 11:59:00 PM

Hi, is there any explanation for the folowing big difference between the sa=
me=20
code in 1.8 and 1.9?:


1.8)

aaa =3D 123.capitalize rescue 444
=3D> 444


1.9)

aaa =3D 123.capitalize rescue 444
NoMethodError: undefined method `capitalize' for 123:Fixnum


It seems that Ruby 1.9 doesn't react on "inline rescue" as 1.8. Do I miss=20
something?

Thanks a lot.



=2D-=20
I=C3=B1aki Baz Castillo
10 Answers

Iñaki Baz Castillo

3/2/2009 12:01:00 AM

0

El Lunes, 2 de Marzo de 2009, I=C3=B1aki Baz Castillo escribi=C3=B3:

> It seems that Ruby 1.9 doesn't react on "inline rescue" as 1.8. Do I miss
> something?

Well, it must be something even worse since block rescue neither works:

=2D----------------
begin
aaa =3D 123.capitalize
rescue
aaa =3D 444
end
=2D-----------------
=3D> NoMethodError: undefined method `capitalize' for 123:Fixnum


Perhaps it's due to the not updated version of Ruby1.9 I'm using?:

$ irb1.9 -v
irb 0.9.5(05/04/13)

$ ruby1.9 -v
ruby 1.9.0 (2007-08-30 patchlevel 0) [i486-linux]


=2D-=20
I=C3=B1aki Baz Castillo

Iñaki Baz Castillo

3/2/2009 12:23:00 AM

0

El Lunes, 2 de Marzo de 2009, I=C3=B1aki Baz Castillo escribi=C3=B3:

> Perhaps it's due to the not updated version of Ruby1.9 I'm using?:
>
> $ irb1.9 -v
> irb 0.9.5(05/04/13)
>
> $ ruby1.9 -v
> ruby 1.9.0 (2007-08-30 patchlevel 0) [i486-linux]

Yes, it seems to be an old bug in my 1.9 version. I've upgraded to:

$ ruby1.9 -v
ruby 1.9.0 (2007-12-25 revision 14709) [i486-linux]

and the "rescue" issue has gone.


=2D-=20
I=C3=B1aki Baz Castillo

Brian Mitchell

3/2/2009 12:30:00 AM

0

On Sun, Mar 1, 2009 at 19:01, I=C3=B1aki Baz Castillo <ibc@aliax.net> wrote=
:
> El Lunes, 2 de Marzo de 2009, I=C3=B1aki Baz Castillo escribi=C3=B3:
>
>> It seems that Ruby 1.9 doesn't react on "inline rescue" as 1.8. Do I mis=
s
>> something?
>
> Well, it must be something even worse since block rescue neither works:
>
> -----------------
> begin
> =C2=A0 =C2=A0 =C2=A0 =C2=A0aaa =3D 123.capitalize
> rescue
> =C2=A0 =C2=A0 =C2=A0 =C2=A0aaa =3D 444
> end
> ------------------
> =3D> NoMethodError: undefined method `capitalize' for 123:Fixnum
>
>
> Perhaps it's due to the not updated version of Ruby1.9 I'm using?:
>
> =C2=A0$ irb1.9 -v
> =C2=A0irb 0.9.5(05/04/13)
>
> =C2=A0$ ruby1.9 -v
> =C2=A0ruby 1.9.0 (2007-08-30 patchlevel 0) [i486-linux]

miro:~ brian$ irb19
>> aaa =3D 123.capitalize rescue 444
=3D> 444
miro:~ brian$ ruby19 -v
ruby 1.9.2dev (2009-03-02 trunk 22700) [i386-darwin9.6.0]

Brian.

Gregory Brown

3/2/2009 2:01:00 AM

0

On Sun, Mar 1, 2009 at 6:58 PM, I=F1aki Baz Castillo <ibc@aliax.net> wrote:
> Hi, is there any explanation for the folowing big difference between the =
same
> code in 1.8 and 1.9?:
>
>
> 1.8)
>
> aaa =3D 123.capitalize rescue 444
> =3D> 444
>
>
> 1.9)
>
> aaa =3D 123.capitalize rescue 444
> NoMethodError: undefined method `capitalize' for 123:Fixnum

>> RUBY_VERSION
=3D> "1.9.1"
>> 123.captialize rescue 444
=3D> 444

But please, don't use this technique. It creates huge debugging nightmares=

Michal Suchanek

3/2/2009 8:19:00 AM

0

2009/3/2 Gregory Brown <gregory.t.brown@gmail.com>:
> On Sun, Mar 1, 2009 at 6:58 PM, I=C3=B1aki Baz Castillo <ibc@aliax.net> w=
rote:
>> Hi, is there any explanation for the folowing big difference between the=
same
>> code in 1.8 and 1.9?:
>>
>>
>> 1.8)
>>
>> aaa =3D 123.capitalize rescue 444
>> =3D> 444
>>
>>
>> 1.9)
>>
>> aaa =3D 123.capitalize rescue 444
>> NoMethodError: undefined method `capitalize' for 123:Fixnum
>
>>> RUBY_VERSION
> =3D> "1.9.1"
>>> 123.captialize rescue 444
> =3D> 444
>
> But please, don't use this technique. =C2=A0It creates huge debugging nig=
htmares.
>
> Instead, just do:
>
> aaa =3D obj.respond_to?(:capitalize) ? obj.capitalize : 444
>
>
I'd see it as a Ruby's failure that the proper check is against DRY.

Thanks

Michal

Michael Fellinger

3/2/2009 10:38:00 AM

0

On Mon, Mar 2, 2009 at 9:23 AM, I=C3=B1aki Baz Castillo <ibc@aliax.net> wro=
te:
> El Lunes, 2 de Marzo de 2009, I=C3=B1aki Baz Castillo escribi=C3=B3:
>
>> Perhaps it's due to the not updated version of Ruby1.9 I'm using?:
>>
>> =C2=A0 $ irb1.9 -v
>> =C2=A0 irb 0.9.5(05/04/13)
>>
>> =C2=A0 $ ruby1.9 -v
>> =C2=A0 ruby 1.9.0 (2007-08-30 patchlevel 0) [i486-linux]
>
> Yes, it seems to be an old bug in my 1.9 version. I've upgraded to:
>
> =C2=A0$ ruby1.9 -v
> =C2=A0ruby 1.9.0 (2007-12-25 revision 14709) [i486-linux]
>
> and the "rescue" issue has gone.

That's still ancient. The latest revision is 22705 and the last stable
release was 1.9.1.

^ manveru

Phlip

3/2/2009 1:47:00 PM

0

Michal Suchanek wrote:

>> aaa = obj.respond_to?(:capitalize) ? obj.capitalize : 444

> I'd see it as a Ruby's failure that the proper check is against DRY.

DRY is most egregious when the duplicated components are far apart from each
other. (And hence harder to spot!) Duplicating things right next to each other
is Mostly Harmless, and it's always the next best thing if you can't think of
the final refactor.

--
Phlip
http://www.zerop...

Gregory Brown

3/2/2009 2:36:00 PM

0

On Mon, Mar 2, 2009 at 3:18 AM, Michal Suchanek <hramrach@centrum.cz> wrote=
:
> 2009/3/2 Gregory Brown <gregory.t.brown@gmail.com>:

>> But please, don't use this technique. =A0It creates huge debugging night=
mares.
>>
>> Instead, just do:
>>
>> aaa =3D obj.respond_to?(:capitalize) ? obj.capitalize : 444
>>
>>
> I'd see it as a Ruby's failure that the proper check is against DRY.

Agreed, but the costs of the elegance of using rescue as a conditional
modifier stack up fast in any moderately complex system.

-greg

--=20
Technical Blaag at: http://blog.majesticseacr...
Non-tech stuff at: http://metametta.bl...
"Ruby Best Practices" Book now in O'Reilly Roughcuts:
http://rubybestpra...

Ken Bloom

3/2/2009 3:17:00 PM

0

On Mon, 02 Mar 2009 09:36:10 -0500, Gregory Brown wrote:

> On Mon, Mar 2, 2009 at 3:18 AM, Michal Suchanek <hramrach@centrum.cz>
> wrote:
>> 2009/3/2 Gregory Brown <gregory.t.brown@gmail.com>:
>
>>> But please, don't use this technique.  It creates huge debugging
>>> nightmares.
>>>
>>> Instead, just do:
>>>
>>> aaa = obj.respond_to?(:capitalize) ? obj.capitalize : 444
>>>
>>>
>> I'd see it as a Ruby's failure that the proper check is against DRY.
>
> Agreed, but the costs of the elegance of using rescue as a conditional
> modifier stack up fast in any moderately complex system.
>
> -greg


The problem with the rescue modifier is that it lumps all types of errors
into one relatively blunt tool. A rescue(Type) modifier would really
help, and a ?. operator (like Groovy's) would resolve one of the most
common cases for a rescue modifier.

--Ken

--
Chanoch (Ken) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu...

Gregory Brown

3/2/2009 3:54:00 PM

0

On Mon, Mar 2, 2009 at 10:38 AM, Ken Bloom <kbloom@gmail.com> wrote:

> The problem with the rescue modifier is that it lumps all types of errors
> into one relatively blunt tool. A rescue(Type) modifier would really
> help, and a ?. operator (like Groovy's) would resolve one of the most
> common cases for a rescue modifier.

Right, if you could do:

obj.capitalize rescue(NoMethodError) 42

it'd remove the debugging issue. However, this does force the
interpreter to do a whole lot of extra work raising and rescuing an
error unnecessarily.

Groovy's ?. looks about right in terms of what we really want most of
the time rescue is used as a conditional modifier.
In the past, I've implemented this as:

class Object
def try(sym, *args)
return if nil?
send(sym, *args) if respond_to?(sym)
end
end

then, you get:

a = obj.try(:capitalize) || 42

But there are obviously some other limitations here...

-greg




--
Technical Blaag at: http://blog.majesticseacr...
Non-tech stuff at: http://metametta.bl...
"Ruby Best Practices" Book now in O'Reilly Roughcuts:
http://rubybestpra...