From: "Matthew K. Williams" <matt@...>
Date: 2009-08-20T02:39:04+09:00
Subject: Re: #has_arguments?

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On Thu, 20 Aug 2009, Trans wrote:

>
>
> On Aug 19, 7:53=A0am, Roger Pack <rogerdp...@gmail.com> wrote:
>>> =A0def meth(*a)
>>> =A0 =A0if !a.empty?
>>> =A0 =A0 =A0a =3D a.first
>>> =A0 =A0 =A0 ...
>>> =A0 =A0else
>>> =A0 =A0 =A0...
>>> =A0 =A0end
>>> =A0end
>>
>> Maybe morph this to
>>
>> def meth(*a)
>> =A0 if has_arguments? a
>> =A0 =A0 ...
>> =A0 else
>> =A0 =A0 ...
>> =A0 end
>> end
>
> Either way is fine. The defined method interface doesn't matter.
> #has_arguments? would simply report false if a call to the method
> passed no arguments. If the interface definition itself does not allow
> for no arguments, eg. 'def meth(a)', then #has_arguments? would simply
> never return false.
>
> T.
>
>

I'm still not convinced this is necessarily needed, but, how about this=20
for a first stab (still looking at whether there's a way to not need the=20
explicit call to binding) :

class Object
   def has_arguments?(b)
     vars =3D eval("local_variables",b)
     return false if vars.length =3D=3D 0
     vars.each do |v|
       return false if eval("#{v}.nil?",b)
     end
     return true
   end
end

class Foo
   def initialize(first=3Dnil)
     if (has_arguments? binding)
       puts "We're defined"
     else
       puts "Not!"
     end
   end

   def no_args
     if (has_arguments? binding)
       puts "We're defined"
     else
       puts "Not!"
     end
   end

   def mandatory_arg(a)
     if (has_arguments? binding)
       puts "We're defined"
     else
       puts "Not!"
     end
   end
end


Matt
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