Hello all,
Is there a way to turn a Proc into a block for the purposes of methods that yield to blocks? It's not a necessity as I can always wrap the Proc in a block, I'm just curious.
Thanks,
Loren
____________________________________________________________________________________
Never miss a thing. Make Yahoo your home page.
Just prefix the object you want to be passed as a block with '&' in the argument list.
p = proc { |x| x > 10 }
[1,5,10,20, 30].select &p
Gary Wright
On Jan 7, 2008, at 11:06 PM, L A wrote:
Hello all,
Is there a way to turn a Proc into a block for the purposes of methods that yield to blocks? It's not a necessity as I can always wrap the Proc in a block, I'm just curious.
Is there a way to turn a Proc into a block for the purposes of methods that yield to blocks? It's not a necessity as I can always wrap the Proc in a block, I'm just curious.
maybe use the & op, like
p=proc{"hi, i'm proc"}
#=> #<Proc:0x028cc40c@(irb):1>
p.call
#=> "hi, i'm proc"
def q
yield
end
#=> nil
q
LocalJumpError: no block given
from (irb):7:in `q'
from (irb):9
q &p
#=> "hi, i'm proc"
(proc &p).call
#=> "hi, i'm proc"
i am not sure why you want to wrap a proc with a block though
proc {p}
#=> #<Proc:0x02898418@(irb):30>
(proc {p}).call
#=> #<Proc:0x028cc40c@(irb):1>
(proc {p}).call.call
#=> "hi, i'm proc"
kind regards -botp
On Jan 8, 2008 12:06 PM, L A <loren.abrams@yahoo.com> wrote:
from :0
Except that this isn't part of the standard ruby library for 1.8. It
relies on having a Symbol#to_proc method
It is a common extension, for example Rails includes it.
It IS part of Ruby 1.9 though.
I'd suggest googling for "ruby to_proc"
On Jan 7, 2008 11:35 PM, Gary Wright <gwtmp01@mac.com> wrote:
On Jan 7, 2008, at 11:06 PM, L A wrote:
> Hello all,
>
> Is there a way to turn a Proc into a block for the purposes of
> methods that yield to blocks? It's not a necessity as I can always
> wrap the Proc in a block, I'm just curious.Just prefix the object you want to be passed as a block with '&' in
the argument list.p = proc { |x| x > 10 }
[1,5,10,20, 30].select &p
--
Rick DeNatale
My blog on Ruby
http://talklikeaduck.denhaven2.com/
Wait... what?
No it doesn't.
[ 1, 5, 10, 20, 30 ].map &:to_a
uses Symbol#to_proc
p = proc { |x| x > 10 }
[1,5,10,20, 30].select &p
is standard ruby syntax, even from 1.6:
"If the last argument to a method is preceded by an ampersand, Ruby
assumes that it is a Proc object. It removes it from the parameter
list, converts the Proc object into a block, and associates it with
the method."
(see Programming Ruby: The Pragmatic Programmer's Guide)
On Jan 8, 8:24 am, Rick DeNatale <rick.denat...@gmail.com> wrote:
On Jan 7, 2008 11:35 PM, Gary Wright <gwtm...@mac.com> wrote:
> On Jan 7, 2008, at 11:06 PM, L A wrote:
> > Hello all,
> > Is there a way to turn a Proc into a block for the purposes of
> > methods that yield to blocks? It's not a necessity as I can always
> > wrap the Proc in a block, I'm just curious.> Just prefix the object you want to be passed as a block with '&' in
> the argument list.> p = proc { |x| x > 10 }
> [1,5,10,20, 30].select &p
Except that this isn't part of the standard ruby library for 1.8. It
relies on having a Symbol#to_proc method
This isn't what I said.
Gary suggested using a symbol as a proc, which requires that Symbol
implement the to_proc method, which is NOT part of standard Ruby prior
to 1.9.
$ qri to_proc
------------------------------------------------------ Multiple choices:
Method#to_proc, Proc#to_proc, Test::Unit::Util::ProcWrapper#to_proc
Now as I pointed out extending Symbol to implement to_proc is quite
common, and many Rails programmers tend to think of the stuff in
ActiveSupport as being standard Ruby, but it isn't.
It's likely that Rails will change ActiveSupport to only add
Symbol#to_proc if using Ruby < 1.9 since 1.9 includes it, but that
doesn't seem to have happened yet.
http://dev.rubyonrails.org/ticket/8818
On Jan 8, 2008 9:05 AM, Noah Easterly <noah.easterly@gmail.com> wrote:
On Jan 8, 8:24 am, Rick DeNatale <rick.denat...@gmail.com> wrote:
> On Jan 7, 2008 11:35 PM, Gary Wright <gwtm...@mac.com> wrote:
> > Just prefix the object you want to be passed as a block with '&' in
> > the argument list.
>
> > p = proc { |x| x > 10 }
>
> > [1,5,10,20, 30].select &p
>
> Except that this isn't part of the standard ruby library for 1.8. It
> relies on having a Symbol#to_proc method
>
Wait... what?No it doesn't.
[ 1, 5, 10, 20, 30 ].map &:to_a
uses Symbol#to_proc
p = proc { |x| x > 10 }
[1,5,10,20, 30].select &pis standard ruby syntax, even from 1.6:
"If the last argument to a method is preceded by an ampersand, Ruby
assumes that it is a Proc object. It removes it from the parameter
list, converts the Proc object into a block, and associates it with
the method."
--
Rick DeNatale
My blog on Ruby
http://talklikeaduck.denhaven2.com/
Rick DeNatale wrote:
Gary suggested using a symbol as a proc
No, he didn't.
--
Jabber: sepp2k@jabber.org
ICQ: 205544826
Rick, you just misread my original post a bit. I didn't mention
Symbol#to_proc at all but I did hint at it by saying you 'just'
prefix the argument with '&'. That sort of begs the question of
what happens if the argument isn't an instance of Proc but I didn't
want to muddy the waters at that point. My example used a proc.
Gary Wright
On Jan 8, 2008, at 10:39 AM, Rick DeNatale wrote:
Gary suggested using a symbol as a proc, which requires that Symbol
implement the to_proc method, which is NOT part of standard Ruby prior
to 1.9.