From: Morton Goldberg <m_goldberg@...>
Date: 2007-05-08T19:22:39+09:00
Subject: Re: Difference answers from Terminal, TextMate, and BBEdit

On May 8, 2007, at 12:30 AM, Greg wrote:

> On 2007-05-07 20:37:31 -0700, Morton Goldberg  
> <m_goldberg@ameritech.net> said:
>
>> 2. Your case statement in the your while loop just doesn't do  
>> what  you think it should. And actually it would be hard make a  
>> case work  in the situation you have set up.
>> Here is a modification of your code that I think will do what you   
>> were trying to achieve:
>> <code>
>> #!/usr/bin/env ruby
>> class OrangeTree
>>     MSG_GROW = "Type \"year\" to grow your tree."
>>     MSG_PICK = "Type a number to pick some more fruit. "
>>     EXIT_TXT = "Something went wrong."
>>     def initialize
>>        @heightInches = 0
>>        @age = 0
>>        @fruit = 0
>>        puts MSG_GROW
>>     end
>>     def ageOneYear
>>        @heightInches = @heightInches +1
>>        puts 'Height: ' + @heightInches.to_s # <= not '@height'
>>        @age += 1
>>        # @age = @age + 1
>>        puts "Got to ageOneYear. Age: #{@age}"
>>        case @age
>>        when (1..3) :  puts("Your #{@age} year old tree is too  
>> young  to bear fruit yet. #{MSG_GROW}" )
>>        when (4..29) : puts(" Age: #{@age}. Place holder until get   
>> 1..3 working." )
>>        when (30) :    puts("Your tree was very fruitful, but it   
>> reached old age and died.")
>>        else puts( " Something went wrong. #{EXIT_TXT}" )
>>        end
>>     end
>>     def height
>>        # returns the height
>>     end
>>     def pick_an_orange
>>        puts 'Got to pick_an_orange, but haven\'t defined yet'
>>        # reduce this year count by one
>>     end
>> end
>> countLoop = 0
>> tree = OrangeTree.new
>> while countLoop < 100
>>     countLoop += 1
>>     puts "countLoop = #{countLoop}"
>>     # case statement not really appropriate for this loop.
>>     # Note: gets always returns a string terminated with a newline.
>>     user_input = gets.chomp
>>     if user_input == 'year'
>>        tree.ageOneYear
>>     elsif (1..100).include?(user_input.to_i) # need to convert  
>> string  to integer
>>        tree.pick_an_orange
>>     else puts('Don\'t be greedy, don\'t try to pick more than 100   
>> oranges')
>>     end
>> end
>> </code>
>> Regards, Morton
>
> No it's not working like I want. But I don't understand why case  
> isn't appropriate. But your method works right and mine doesn't, so  
> I don't think I'll worry about it now.

You _could_ use a case here, but it would have to be considerably  
more complicated than the simple case form you wrote. I thought (and  
still think) an if-elsif-else statement is better for sorting out the  
user input in this case. A case statement like

<code>
case
when 'year' : tree.ageOneYear # , y as shortcut?
when (1..100) : tree.pick_an_orange
else puts('Don\'t be greedy, don\'t try to pick more than 100  oranges')
end
</code>

just looks for the first true when-clause. In this case that will  
always be 'year' because everything but false and nil is true in Ruby.

> One question. How is
>>  elsif (1..100).include?(user_input.to_i)
> working? I understand it up through "elsif(1..100)" Is the  
> user_input changed to integer before the elsif is evaluated. What  
> does the include? do? (The don't be greedy part was just  
> placeholder until I worked out the whole orange picking and growing  
> logic.)

user_input is converted to a integer during the evaluation of the  
elsif. This code is roughly equivalent to:

num = user_input.to_i
in_range = (1..100).include?(num)
elsif in_range
    ...

> BTW, the while loop seemed like a crude work around to keep asking  
> for inputs. I would like it to stop at 30 in the class (at least  
> that seems more elegant as that is where the age decisions are made).

Do you want to stop after 30 loops (that's easy) or when @age reaches  
30 (that's just a little harder)? For the first:

<code>
tree = OrangeTree.new
30.times do
    user_input = gets.chomp
    if user_input == 'year'
       tree.ageOneYear
    elsif (1..100).include?(user_input.to_i) # need to convert string  
to integer
       tree.pick_an_orange
    else puts('Don\'t be greedy, don\'t try to pick more than 100  
oranges')
    end
end
</code>

For the second:

<code>
class OrangeTree
    attr_reader :age # <= add this to OrangeTree so @age can be  
queried outside of class def
end
tree = OrangeTree.new
loop do
    user_input = gets.chomp
    if user_input == 'year'
       tree.ageOneYear
       break if tree.age >= 30
    elsif (1..100).include?(user_input.to_i) # need to convert string  
to integer
       tree.pick_an_orange
    else puts('Don\'t be greedy, don\'t try to pick more than 100  
oranges')
    end
end
</code>

Regards, Morton