From: "Hakusa@..." <Hakusa@...>
Date: 2007-05-25T23:30:03+09:00
Subject: Array troubles

I'm converting a Java calculator program I wrote into Ruby--which,
just so you know, has been unbelievable with how quickly the language
can be learned and implemented and how easy it made programming what
had taken months of Java (but that was during school-time so
development was, admittedly, very slow)--but I've run into a problem.

In a term, if you have q/q^2/4/8, it turns into q^-1/.5, but I'm
getting q^-10! I've narrowed it down to one part of one function:
division in Term#simplify.

There's a lot of code involved, so I'll only post relevant data. I
REALLY do think you'll need any more than this. Also: when I say
algebraic calculator, I mean that half the time you're working with
letters (variables), not numbers.

Term#simplify

>>def simplify
>>        count=0 # count will keep track of iterations.
>>        temp = [] # This array will be our temp for @items.
>>       @items.each do |item|
>>
>>            # Why check for this?
>>            # The only time strings are use here is as an operator.
>>            if item.class == String
>>                # Defining these really just make the code easier for further on.
>>                # They're the items before and after the operator.
>>                num1 = @items[count-1]
>>                num2 = @items[count+1]
>>
>>                # So if the operator is division...
>>                if item.eql?('/')
>>                    # You can't do much if the operands aren't of the same class.
>>                    if num1.class.eql?( num2.class )
>>                        puts 'temp pre ' + (temp).to_s
>>                        # And use the / method of whatever class they are.
>>                        puts num1.to_s + item + num2.to_s + " = " +
>>                            (num1/num2).to_s
>>                        temp << num1/num2
>>                        puts 'temp post ' + (temp).to_s
>>                    end
>>                end
>>            end
>>            count += 1
>>        end
>>        puts temp[1]
>>        temp
>>    end

With q/q^2/4/8 it prints out

>> temp pre
>> q/q^2 = q^-1
>> temp post q^-1
>> temp pre q^-1
>> 4/8 = 0
>> temp post q^-10
>> 0

Interestingly enough, 4/8=0. I don't know how the hell that works.
Also, when it goes around for the second time to get 4/8, it puts it
in the first place in the array (array[0]) and not the next space,
which is where I thought this method is supposed to put it. ri must
have this wrong too.

I don't think you need to know how I divide variables, but just in
case you do:

>>    # Return the result of this instance and var1.
>>    # Assumes that the two are like.
>>    def /(var)
>>        Variable.new(self.base, (self.exponent-var.exponent))
>>    end

A variable is just a string base and integer exponent.

PS: I would accept some criticism as long as it's productive, but I do
know that my code is lacking in certain areas (like how it doesn't
check whether or not the variables have like bases), but it is a WIP.