From: ts <decoux@...>
Date: 2000-12-22T02:51:03+09:00
Subject: [ruby-talk:7895] Re: defined? problem?

>>>>> "c" == craig duncan <duncan@nycap.rr.com> writes:

c> if not defined? i

 for this line, ruby think that `i' is a method (`i' was never defined as a
local variable before this statement)

 At runtime because the method `i' is not defined it will
enter in the if and execute :

c>   i = 0

 this time `i' make reference to a local variable (because you make an
 assignment) and is initialized at 0

c> end

c> p i += 1

c> j = 0 if not defined? j

 At compile time, ruby resolve `j' as a reference (in the 2 cases) to a
 local variable, because `j = 0' was seen *before* `defined? j'

 At runtime, because `j' is a local variable, it is also defined and ruby
 don't execute the code `j = 0' this mean that j contain nil

c> p j += 1

 it give an error `+' is not defined for nil (i.e. `j')


Guy Decoux