From: Austin Ziegler <halostatue@...>
Date: 2006-01-20T22:05:55+09:00
Subject: Re: strict pragma & scope

On 20/01/06, Tom Allison <tallison@tacocat.net> wrote:
> I'm still reading "the book" and am trying to see if I got this right.
> Sometimes the book isn't direct enough on "this is how you will be programming
> in ruby".

This is, in part, because not everyone programs in Ruby quite the same
way. I know that my style is very distinctive from others' style (and
my style is pretty "mainstream," nonetheless).

> Is there anything like perl strict pragma in ruby?

Not quite, but Ruby is more strict than Perl in any case. Running ruby
-w (even in your bangpath line) will give you more information.

> Scope.  It seems that there are some different approaches to scope.  For
> example, objects created in a loop remain in scope after you leave the scope of
> the iterator.  So my favorite temporary variables of i, x, foo, and bar are all
> now permanent variable elements in my code blocks from their first use.
> True/False?

I believe that if you do a "for" loop, your statement is true.

irb(main):001:0> (1..10).each { |i| }
=> 1..10
irb(main):002:0> i
NameError: undefined local variable or method `i' for main:Object
        from (irb):2
irb(main):003:0> for i in 1..10
irb(main):004:1> end
=> 1..10
irb(main):005:0> i
10

The idiomatic way to loop in Ruby is with #each or other iterator items.

Now, if you've defined i *outside* of your iterator, current Ruby will
overwrite it.

irb(main):001:0> i = 0
=> 0
irb(main):002:0> (1..10).each { |i| }
=> 1..10
irb(main):003:0> i
=> 10

I believe that there will be changes to this moving forward, but I
can't remember the exact scope changes.

-austin
--
Austin Ziegler * halostatue@gmail.com
               * Alternate: austin@halostatue.ca