Problem with aliasing String#index

[Niklas Frykholm]

Aliasing String#index:

"rollo".index(/../, 1)
puts "noalias #{$~}"

class String
alias old_index index

def index(*arg)
ret = old_index(*arg)
puts "inside #{$~}"
return ret
end
end

"winni".index(/../, 3)
puts "outside #{$~}"

gives

noalias ol
inside ni
outside ol

To fully duplicate the functionality of the built-in String#index I need
to transfer $~ from the local scope to the enclosing scope. Is there any
way of doing this?

// Niklas

 

[Florian Gross]

To fully duplicate the functionality of the built-in String#index I need
to transfer $~ from the local scope to the enclosing scope. Is there any
way of doing this?

There's a solution in the ruby-talk:79283 thread that was posted by
matz, but it's not thread safe. It would be wonderful if we could have a
proper way of doing this...

 

[Niklas Frykholm]

There's a solution in the ruby-talk:79283 thread that was posted by
matz, but it's not thread safe. It would be wonderful if we could have
a proper way of doing this...

Ah... interesting... but that technique doesn't really work with
String#index, since String#index doesn't take a block.

I think I just have to resign from the idea of making a completely
transparent String wrapper.

But it would be nice if this was resolved. In principle, I think it
should be possible to do the same things from Ruby as from C. I.e. if C
can set a variable $~ in the caller's scope, it should be possible to do
that from Ruby as well.

// Niklas

 

[Patrick Hurley]

Thanks for that code, I was lurking reading this thread and have been
wondering all day how to implement that, because of you I will get a
good nights sleep.

pth

 

[Niklas Frykholm]

Indeed. See attachment, Binding.of_caller.

Nice. Thanks a lot. I will probably be able to put that to use.

// Niklas