From: rak rok <rakrok@...>
Date: 2006-08-25T03:05:40+09:00
Subject: Re: do not understand this closure

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Is there any way to have a proc object be callable identically to a method,
ie with the parentheses?  Is there a reason to keep the notation distinct?

Thanks,
-rr-


On 8/24/06, Martin DeMello <martindemello@gmail.com> wrote:
>
> On 8/24/06, Dave Rose <bitdoger2@yahoo.com> wrote:
> > in The Ruby Way...chap 1...a crude example of closure doesn't work as
> > this irb
> > session:
> > >> def power(exponent)
> > >>  proc {|base| base**exponent}
> > >> end
> > => nil
> > >> square = power(2)
> > => #<Proc:0x02dc58f0@(irb):2>
> > >> cube = power(3)
> > => #<Proc:0x02dc58f0@(irb):2>
> > >> p square
> > #<Proc:0x02dc58f0@(irb):2>
> > => nil
> > >> square(11)
> > NoMethodError: undefined method `square' for main:Object
> >         from (irb):7
>
> You want square[11] or square.call(11)
>
> square(11) is interpreted as "call the method 'square' on the current
> "self" object, with the argument '11'", whereas square[11] is
> interpreted as "call the method [] on the object 'square' with the
> argument 11. Proc defines [] to be a synonym of call.
>
> martin
>
>

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