[ruby-core:22636] Re: Question: lambda and yield

03.03.2009, 7:46, Jacob Fugal 轢闊騾:

> Take the following with a grain of salt; I'm not a core expert, I just
> play one on TV. ;) If I'm wrong, just let me know. That said, I'm
> pretty sure that...
>
> Try the following code. You'll see that the puts after the yield isn't
> even evaluated. The return statement within the lambda is "bound" (for
> lack of a better word) to the method where the lambda was defined, not
> the lambda itself. The statement is rebound to the Proc object when
> the lambda is converted to a Proc, but remains bound to the caller
> when yielded to.

Thank you for you reply.

This 澱oundpiece of puzzle is missing from my view. I quick-check  
ruby 1.8.6 code and there's no explicit 途ebounding it looks for the  
Proc object type in call method, and does not look in rb_yield  
(assumes everything is Proc.new). I just wanted to know this  
澱oundingis expected behavior  or not.


>
> Moral of the story: avoid return in lambdas and procs unless you
> really want to explode a later code reader's brain. :)
>
> Jacob Fugal
>
> --
> def call_block(&l)
>  l.call
> end
>
> def yield_block
>  yield
> end
>
> def lambda_and_call
>  l = lambda { return 1 }
>  x = call_block(&l) + 1
>  puts "lambda_and_call: #{x}"
> end
>
> def lambda_and_yield
>  l = lambda { return 1 }
>  x = yield_block(&l) + 1
>  puts "lambda_and_yield: #{x}"
> end
>
> lambda_and_call
> lambda_and_yield
>