Computer Science Canada

ripple carry adder
Author:  Insectoid [ Thu Oct 09, 2008 12:57 pm ]
Post subject:  ripple carry adder
Hi,

I decided to try to make a ripple carry adder. Because I'm like that, I decided to do it recursively. I am rather new to arrays in Java, which I wanted to use, and so I did. This is my first time using a non-static method, and it is a little bit over my head. The adder works (I did a half-adder and a full adder, now I'm adjusting the full adder to create my ripple carry adder, so the math bit works).

The problem? Lots of them. Mostly syntax, but I can't find the problems. It says I need identifiers where there are identifiers, that I'm missing ';' on lines that have them, etc.

Right now, it only has static input, so true = 1 and false = 0. Eventually I'll add in a binary converter, but right now, I want what I have to work.

Here's my code:

code:

public class full_adder {

   
    public static void main (String [] args) {
        int size_array = 1;
        boolean []in_A =new boolean [size_array];
                boolean []in_B =new boolean [size_array];
        in_A [0] = true;
        in_A [1] = false;
        in_B [0] = false;
        in_B [1] = true;
                boolean in_C = false;
        boolean [] sum = new boolean [size_array];
        boolean out_C = false;
        int counter = 0;
     
       
    }   
   
    public static boolean adder (boolean a, boolean b, boolean c){
        sum [counter] = (a ^ b)^c;
        out_C = (a && b)||((a ^ b)&&c);
        counter += 1;
        return out_C;
        if (counter <=  size_array) {
       
        adder (in_A [counter], in_B [counter], out_C);
        }
    }
}
Author:  [Gandalf] [ Thu Oct 09, 2008 3:24 pm ]
Post subject:  RE:ripple carry adder
You're declaring variables in the scope of main() and then trying to use the in adder(). You'll have to pass them to adder() as parameters or make them instance variabeles and make an object of your class or make them static. [/rushed post]
Author:  wtd [ Thu Oct 09, 2008 3:40 pm ]
Post subject:  RE:ripple carry adder
Also worth noting:

code:
    public static boolean adder (boolean a, boolean b, boolean c){
       sum [counter] = (a ^ b)^c;
       out_C = (a && b)||((a ^ b)&&c);
       counter += 1;
       return out_C;
       if (counter <=  size_array) {
       
       adder (in_A [counter], in_B [counter], out_C);
       }
    }


Once you "return out_C" that's the end of execution for the method. The conditional is not evaluated.
Author:  Insectoid [ Thu Oct 09, 2008 3:47 pm ]
Post subject:  RE:ripple carry adder
@ wtd-well...thanks. All I had to go on for this was a rushed explanation by my teacher about functions and returning variables.

How do I declare instance variable? Is a variable declared inside a method local to that method? Would I declare them outside a method? Outside the class? My complete new-ness to object oriented programming is showing, isn't it?

Edit: I changed some things, but now I get this error:

code:

Syntax error on token "(", ; expected
        Syntax error on token ")", ; expected
        Syntax error, insert "}" to complete Block
        Syntax error, insert "}" to complete ClassBody

        at ripple_carry_adder.main(ripple_carry_adder.java:15)


it refers to this line:
code:
public static void main (String args []){
    }


Do I really need a 'main', or is it just something people do?
Author:  wtd [ Thu Oct 09, 2008 4:21 pm ]
Post subject:  RE:ripple carry adder
http://wiki.compsci.ca/index.php?title=Introduction_To_Java
Author:  Insectoid [ Thu Oct 09, 2008 6:58 pm ]
Post subject:  RE:ripple carry adder
Okay, I changed some stuff around, but there are some errors still. I suppose it is caused by variables declared in 'main' being used in 'adder'. How do I counter this? Is there a way to make variables universal? Such that any method can use/manipulate them?

Code:

Java:

public class ripple_carry_adder {
       
   
    public static void main (String args []){
        boolean [] sum = new boolean [size_array];
        int size_array = 2;
        boolean []in_A = new boolean [size_array];
        boolean []in_B = new boolean [size_array];
         in_A [0] = true;
         in_A [1] = false;
         in_B [0] = false;
         in_B [1] = true;
         boolean in_C = false;
         
        boolean out_C = false;
        int counter = 0;
        adder (in_A [0], in_B [0], in_C);
    }   
   
    public static void adder (boolean a, boolean b, boolean c){
       
        sum [counter] = (a ^ b)^c;
        out_C = (a && b)||((a ^ b)&&c);
       
        counter += 1;
        if (counter <=  size_array) {       
                adder (in_A [counter], in_B [counter], out_C);
       }
    }
}
Author:  [Gandalf] [ Thu Oct 09, 2008 7:10 pm ]
Post subject:  RE:ripple carry adder
Yes, keep reading wtd's tutorial, it's all in there and more. Go step by step, when you're done (or at least well into it) none of this should be a problem, and you'll gain understanding far beyond the scope of this assignment. Smile
Author:  Insectoid [ Thu Oct 09, 2008 7:19 pm ]
Post subject:  RE:ripple carry adder
Oh, this isn't an assignment. I'm doing it for fun. My engineering teacher challenged my to just do the schematic diagram for a half-adder, and having done that, I decided to try to program it!
Author:  Insectoid [ Thu Oct 09, 2008 7:34 pm ]
Post subject:  RE:ripple carry adder
Okay, double posting time!

I looked over the tutorial some more, and found out about private variables and stuff, then my editor (eclipse) told me to make the some variables static, so I did, and now have one error,

code:

Exception in thread "main" java.lang.Error: Unresolved compilation problem:

        at ripple_carry_adder.main(ripple_carry_adder.java:13)


full code:
Java:

public class ripple_carry_adder {
        private static boolean [] sum = new boolean [size_array];
        private int size_array = 2;
    private static boolean []in_A = new boolean [size_array];
    private static boolean []in_B = new boolean [size_array];

     private static boolean in_C = false;
     
    private boolean out_C = false;
    private int counter = 0;
   
    public static void main (String args []){
        in_A [0] = true;
        in_A [1] = false;
        in_B [0] = false;
        in_B [1] = true;        
        adder (in_A [0], in_B [0], in_C);
    }   
   
    public static void adder (boolean a, boolean b, boolean c){
       
        sum [counter] = (a ^ b)^c;
        out_C = (a && b)||((a ^ b)&&c);
       
        counter += 1;
        if (counter <=  size_array) {       
                adder (in_A [counter], in_B [counter], out_C);
       }
    }
}
Author:  Clayton [ Thu Oct 09, 2008 8:04 pm ]
Post subject:  RE:ripple carry adder
What's going on with your indentation? Stick with a consistent indentation, otherwise your code is horrible to try and read.

Also, on your naming scheme, it is common practice (actually, it's the standard) to use camelCase when naming variables and methods, CamelCase when naming classes, and UPPER_CASE when naming constants.
Author:  Insectoid [ Thu Oct 09, 2008 8:07 pm ]
Post subject:  RE:ripple carry adder
I'll eventually get into the gist of it. I really do enjoy underscores. So everybody will know it's my code!
Author:  Clayton [ Thu Oct 09, 2008 8:13 pm ]
Post subject:  RE:ripple carry adder
There exists a standard for a reason. You'll find it's much easier to get help from a large community such as the one that is behind Java if you stick to those standards. It's good to get into the habit of using them.
Author:  Insectoid [ Thu Oct 09, 2008 8:21 pm ]
Post subject:  RE:ripple carry adder
I suppose the indentation is the result of the lack of Turing's F2. Fine, I'll work on my naming conventions...
Author:  OneOffDriveByPoster [ Thu Oct 09, 2008 8:25 pm ]
Post subject:  Re: RE:ripple carry adder
insectoid @ Thu Oct 09, 2008 8:21 pm wrote:
I suppose the indentation is the result of the lack of Turing's F2. Fine, I'll work on my naming conventions...
Eclipse has some of the best auto-indenting available.
Author:  wtd [ Thu Oct 09, 2008 8:46 pm ]
Post subject:  RE:ripple carry adder
Yes. I like underscores too, but reading Java code with them used extensively makes me want to gouge out my eyeballs even more than reading Java code usually does.
Author:  Insectoid [ Fri Oct 10, 2008 10:47 am ]
Post subject:  Re: RE:ripple carry adder
OneOffDriveByPoster @ Thu Oct 09, 2008 8:25 pm wrote:
insectoid @ Thu Oct 09, 2008 8:21 pm wrote:
I suppose the indentation is the result of the lack of Turing's F2. Fine, I'll work on my naming conventions...
Eclipse has some of the best auto-indenting available.


How? I'm new to eclipse.
Author:  andrew. [ Wed Oct 15, 2008 2:49 pm ]
Post subject:  RE:ripple carry adder
It's CMD + I on Mac. I suppose it would be CTRL + I on Windows.
Author:  Insectoid [ Wed Oct 15, 2008 3:46 pm ]
Post subject:  RE:ripple carry adder
Well, I'm on a mac, so I guess it's CMD+I for me.

I got it working now, so I'm just adding in the UI, which requires a decimal-binary converter and many int-to-string commands. Basically, it's a lot of easy stuff that takes a lot of time. Fun. Sad.

:


You can syndicate this boards posts using the file backend.php or view the topic map using sitemap.php.

Terms of Use | Privacy Policy