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    <p>Interesting problem. You are basically building a simple virtual processor of boolean values. So I would build the simulator as more of a processor. So essentially you'll have registers (input, output, or internal registers), then the logic would define your operands. Since you are only dealing with boolean logic it's pretty easy to come up with a set of operands that you need: AND, OR, NOT, XOR. For things like &amp;&amp;, || those operands will have two inputs and one output. But, for NOT you'll have only one input and one output. So I'd create a Class for each operand you want to support. And either an abstract Class or interface all operands extend/implement. That will provide the interface for the client to evaluate each operand in the same manner and execute the program.</p> <p>For example:</p> <pre><code>public class AndOperation implements Operand, Argument { private Argument argument1; private Argument argument2; private String output; public AndOperation( Argument arg1, Argument arg2 ) { this( arg1, arg2, null ); // this is for chaining where no output exists. } public AndOperation( Argument arg1, Argument arg2, String output ) { this.argument1 = arg1; this.argument2 = arg2; this.output = output; } public boolean evaluate() { return argument1.evaluate() &amp;&amp; argument2.evaluate(); } public String getOutputRegister() { return output; } } public interface Argument { public boolean evaluate(); } public class Register implements Argument { private String name; private boolean value; public boolean evaluate() { return value; } public void setValue( boolean value ) { this.value = value; } } public class Program implements Iterable&lt;Operand&gt; { public Map&lt;Register&gt; registers; public List&lt;Operand&gt; operands; public void parse( InputStream stream ) { // this will take in a stream, parse it, and create the // program. Create the registers, and operands used // to evaluate the program } public void evaluate() { for( Operand op : operands ) { evaluate( op ); } } public void evaluate( Operand operand ) { boolean output = op.evaluate(); String name = op.getOutputRegister(); Register register = registers.get( name ); register.setValue( output ); } public Iterator&lt;Operand&gt; iterator() { return new Debugger( this ); } } public class Debugger implements Iterator&lt;Operand&gt; { private Program program; private int line = 0; public boolean hasNext() { return line &lt; program.size(); } public Operand next() { Operand operand = program.getOperands().get( line ); program.evaluate( operand ); line++; return operand; } } </code></pre> <p>That's roughly it. However, one thing I wanted to point out was how chaining multiple operands together can be transparently done. The operand doesn't care if it's reading its input from a register or another operand. Since the Register and Operand implements Argument then it substituted for either. So for example:</p> <pre><code>Operand op = new AndOperand( register1, new OrOperand( register2, register3 ); boolean output = op.evaluate(); // this is register1 &amp;&amp; (register2 || register3 ) </code></pre> <p>Of course the tricky part is going to be parsing it, but that's a little difficult to show in this limited space. As far as graphically representing this you could build something that took this program and evaluated it operand by operand and rendered it to the screen in some way. It's possible to build a debugger off of this without much more effort. Just need a little more information that your parser could create (line number to operand map would be helpful).</p>
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    1. COThank you for the response, this gives me a lot to think about.
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    2. COI'm running into a problem now with recursion. When I have a statement like this: `Bit1 = Bit2 + Bit1` Basically, since Bit1 evaluates to OrOperand( Bit2, Bit1 ), when it gets to Bit1 in the statement it continuously evaluates the same thing over and over: `OrOperand( Bit2, OrOperand( Bit2, OrOperand( Bit2, Bit1 ) ) )` Any suggestions on dealing with this? I know I didn't show an example of it in the question. I didn't think posting my full source would be all that helpful, but I can if requested.
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    3. COI'm not sure how it could repeat the same line over and over. I'd expect that line to be parsed as new OrOperand( registerBit1, registerBit2, registerBit1 ) which if eval'ed it wouldn't continuously loop given just what I wrote in the code above. If it's looping I'd check the ops in the program and see if it's create long chains when it shouldn't. Parse your input, then set a breakpoint so you can look into the Program instance. See if it's created any excessive loops. It's not recursion per se it's a statement where a register is used as both input AND output. It's not repeating of statement.
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