From: Florian Gilcher <flo@...>
Date: 2008-05-23T19:20:17+09:00
Subject: Re: Why can't I define vars in caller's binding using eval?

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As far as i know, this is because local variables have a lexical scope.

In my experience, the parser treats everything that was not mentioned  
as a
local variable before a method call and the runtime doesn't check  
whether
it is a variable.

This also explains why IRB works differently, as every statement is  
compiled
as a single statement.

Because of this, it is also impossible to assume the existance of  
local variables
when executing a Proc in a certain context. (without considering hefty  
AST-Hacking
with ruby2ruby).


Regards,
Florian Gilcher

On May 23, 2008, at 11:13 AM, Heesob Park wrote:

> 2008/5/23 Andrew Mitchell <amitchell@ttcent.com>:
>> Christopher J. Bottaro wrote:
>>> In other words, why can't I do this?
>>>
>>> def f(b)
>>>  eval("x = 10", b)
>>> end
>>>
>>> f(binding)
>>> puts "x = #{x}"
>>>
>>> Is there any way to make that code work (besides obviously setting x
>>> to something before calling f).
>>>
>>> Thanks.
>>
>> Worked for me.
>>
>> Dios:~ andrewmitchell$ irb
>>>> def f(b)
>>>> eval("x=10", b)
>>>> end
>> => nil
>>>> f(binding)
>> => 10
>>>> puts "x = #{x}"
>> x = 10
>> => nil
>>>>
> But it works only in irb.
>
> Regards,
>
> Park Heesob
>

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