Strange behaviour regarding lexical scopes?

[Michal]

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.

 

[Robert Klemme]

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