From: adamon@... (Damon)
Date: 2002-06-13T02:02:24+09:00
Subject: Re: ruby-dev summary 17252-17356

Dave Thomas <Dave@PragmaticProgrammer.com> wrote in message > > In that case, what does the semicolon mean?
> 
> It separates parameters from variables which are local to the block.
> 
> 
>     a = 1
>     i = 2
>     (1..10).each do |i|
>       a = i*i
>     end
> 
>     p a   #=> 100
>     p i   #=> 10
>  
> ..
> 
>     a = 1
>     i = 2
>     (1..10).each do |i;a|
>       a = i*i
>     end
> 
>     p a   #=> 1
>     p i   #=> 10
> 
> and I assume
> 
>     a = 1
>     i = 2
>     (1..10).each do <i;a>
>       a = i*i
>     end
> 
>     p a   #=> 1
>     p i   #=> 2
> 

How about:

a = 1
i = 2

(1..10).each with{a} do |i|
	a = i*i
end

p a #=> 100
p i #=> 2


a = 1
i = 2

(1..10).each with{a,i} do |i|
	a = i*i
end

p a #=> 100
p i #=> 10


a = 1
i = 2

(1..10).each do |i|
	a = i*i
end

p a #=> 1
p i #=> 2

a = 1
i = 2

(1..10).each do with{i} |i|
	a = i*i
end

p a #=> 1
p i #=> 10

That is: Modifications to a block variable are visible outside of the
block only if explicitly specified using a 'with' cause.

To put it another way, variables are passed into the block "by value".
Only if specified using a 'with' clause are they passed in "by
reference".
If a variable is passed in "by value" then any changes made to that
variable are restricted to the block; thus we get shadowing for free.

Damon