From: Arlen Christian Mart Cuss <celtic@...>
Date: 2007-11-06T14:18:59+09:00
Subject: Re: Affecting variables inside a while loop that are initialised	outside its scope

Hi,

On Tue, 2007-11-06 at 13:05 +0900, Rawn wrote:
> How can I do it? Sorry if this is stupid or something but I'm just
> learning to program (starting with ruby) and this seemed like a more
> interesting way to start than endless arithmatic operations..
> 
> #!/usr/bin/ruby
> Inventory = Array.new
> Discovered = Array.new
> Victory = 0
> puts "You are in a dim room. You can just make out a door by the light
> shining through the cracks."
> while Victory < 1
> 	inputcommand = gets.chomp!
> 	if inputcommand = "search"
> 		Victory + 1 == Victory
> 	end
> end
> 
> 
> I'd like to change the value of Victory to 1 when "search" is typed
> into the prompt, thus causing the while loop to end, ending the
> script. This may be the completly wrong way to go about doing this but
> atleast tell me how to do what I want before you school me in the
> proper way of doing things ; )
> thanks in advance

Firstly, something to become used to is that in Ruby, anything beginning
with a capital letter is a constant! Watch:

irb(main):001:0> Victory = 1
=> 1
irb(main):002:0> Victory = 2
(irb):2: warning: already initialized constant Victory
=> 2
irb(main):003:0> 

This basically means you should leave capital letters at the start of
names for values which don't change -- for example, there's this
constant:

irb(main):003:0> RUBY_VERSION
=> "1.8.6"
irb(main):004:0> 

That's built-in to Ruby, and of course it's not changing, so it's
rightfully a constant. So, your variable may need to be called 'victory'
instead.

Secondly, to assign a new value to 'victory', just do it like this:

irb(main):002:0> victory = 0
=> 0
irb(main):003:0> victory = victory + 1
=> 1
irb(main):004:0> victory = victory + 1
=> 2
irb(main):005:0> 

Notice the way `victory' is evaluated on the right-hand side first, then
it's all assigned to `victory' on the left. There's even a shorthand for
adding to a variable:

irb(main):005:0> victory += 1
=> 3
irb(main):006:0> victory += 1
=> 4
irb(main):007:0> 

You'll learn a lot more about this as you advance in your Ruby.

Finally, I'll let you know that "==" is for testing equality, whereas
"=" is always for assigning:

irb(main):010:0> victory == 3
=> false
irb(main):011:0> victory == 4
=> true
irb(main):012:0> victory == 5
=> false
irb(main):013:0> 

So, == doesn't change the variable - it just returns 'true' or 'false'
like some other comparison operators do:

irb(main):013:0> victory < 5
=> true
irb(main):014:0> victory <= 2
=> false
irb(main):015:0> 

These are what you use with 'if' or 'while' and similar constructs.
(this is why you need to take care when writing them not to forget an
extra '=' sign!)

Good luck!

Arlen