Strange behaviour regarding lexical scopes?

ruby-talk
1

Hello,

today (when explaining bits of Ruby to my friend)
I got confused by this:

$ cat a.rb
b = 4
if b == 1
    a = 1
end
p a

$ ./a.rb
nil

$ ruby --version
ruby 1.8.2 (2004-07-29) [i686-linux]

(latest gentoo ebuild)

Why is it that 'a' is nil and not undefined? (i would expect:

undefined local variable or method `a' for main:Object (NameError)

)

Thanks in advance,
                      M.

···

--
# Michal Safranek, email:
a=(("a".."z").to_a+["@","."]);p(("%b"%[0x645bbb83a6a496]
).scan(/...../).map{|x|a[Integer("0b"+x)]}.join.reverse)

2

"Michal" <lists+rubytalk@box.cz> schrieb im Newsbeitrag
news:20040827095945.GB26572@box.cz...

Hello,

today (when explaining bits of Ruby to my friend)
I got confused by this:

$ cat a.rb
b = 4
if b == 1
    a = 1
end
p a

$ ./a.rb
nil

$ ruby --version
ruby 1.8.2 (2004-07-29) [i686-linux]

(latest gentoo ebuild)

Why is it that 'a' is nil and not undefined? (i would expect:

undefined local variable or method `a' for main:Object (NameError)

)

Thanks in advance,
                      M.

"if" doesn't introduce a new scope, similar to "switch" in C et. al. So "a"
and "b" reside really in the same scope and the definition in the true
clause is sufficient to make "a" defined. The assignment need not be
executed.

Kind regards

    robert