From: Florian Gilcher <flo@...>
Date: 2009-03-22T17:01:25+09:00
Subject: Re: Passing a named function instead of a code block?


On Mar 22, 2009, at 4:20 AM, 7stud -- wrote:

> James Coglan wrote:
>
> Thanks for the explanation.  You said that (&) casts between block and
> Procs.  But (&) also appears to be casting a Method to a block in this
> line:
>
> puts c.collect(&method(:fib))
>
> (&) can also be used to cast in the reverse direction, e.g. from a  
> block
> to a Proc:
>
> def test(&aProc)
>  aProc.call(10)
> end
>
> test {|x| puts x}
>
> --output:--
> 10
>
>
> Can (&) cast a block to a Method?


There are no casts in Ruby.

& in a Method call calls #to_proc on an Object and expects it to  
return a proc. Thats a conversion that has to be done explicitly by  
the programmer.

& in a Method definition indicates that the argument has to be a Proc  
or something that responds to #to_proc (or a passed Block) which then  
gets enforced.

Blocks are Procs (AFAIK, internally, Methods are basically procs as  
well). The only magic is "yield" together with a block, which to my  
knowledge doesn't require the construction of a Proc Object that has  
to be visible to the programmer. But thats up to the implementation.

Regards,
Florian

--
Florian Gilcher

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