Any way to evaluate blocks using an arbitrary Binding?

ruby-talk
1

Using Kernel.eval, I can evaluate a Ruby string under an arbitrary variable Binding object. However, while I can obtain from a Proc the Binding it uses when it is evaluated, there does not seem to be any way of evaluating a Proc with a different Binding. Is this possible in some way?

Thanks,
Ken

2

Sort of: you can use instance_eval and class_eval with a block. While only "self" will be rebound this is sufficient in many cases.

Kind regards

  robert

···

On 31.08.2007 00:58, Kenneth McDonald wrote:

Using Kernel.eval, I can evaluate a Ruby string under an arbitrary variable Binding object. However, while I can obtain from a Proc the Binding it uses when it is evaluated, there does not seem to be any way of evaluating a Proc with a different Binding. Is this possible in some way?

3

Robert,

I was already aware of instance_eval (have to look up class_eval) used in this manner (possibly from another of your very useful postings), but had wondered if there was a more general way of affecting the execution environment. Oh well.

Thanks,
Ken

Robert Klemme wrote:

···

On 31.08.2007 00:58, Kenneth McDonald wrote:

Using Kernel.eval, I can evaluate a Ruby string under an arbitrary variable Binding object. However, while I can obtain from a Proc the Binding it uses when it is evaluated, there does not seem to be any way of evaluating a Proc with a different Binding. Is this possible in some way?

Sort of: you can use instance_eval and class_eval with a block. While only "self" will be rebound this is sufficient in many cases.

Kind regards

    robert

4

Kenneth McDonald wrote:

Robert,

I was already aware of instance_eval (have to look up class_eval) used in this manner (possibly from another of your very useful postings), but had wondered if there was a more general way of affecting the execution environment. Oh well.

You can change the binding one variable at a time:

def foo
   x = 1
   proc {puts "x = #{x}"}
end

pr = foo

p eval("x", pr)
eval("x=2", pr)
p eval("x", pr)

pr.call

__END__

Output:

1
2
x = 2

···

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       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407