source: branches/PushGP/HeuristicLab.Algorithms.PushGP/HeuristicLab.Algorithms.PushGP/Expressions/DoRangeExpressions.cs @ 14392

using HeuristicLab.Algorithms.PushGP.Interpreter;
using HeuristicLab.Algorithms.PushGP.Stack;

namespace HeuristicLab.Algorithms.PushGP.Expressions
{
    public abstract class DoRangeExpression : LoopExpression
    {
        public DoRangeExpression(string stringRepresentation) : base(stringRepresentation) { }

        protected override bool HasInsufficientArguments(IInterpreter interpreter, IStack<Expression> sourceStack)
        {
            return interpreter.IntegerStack.Count < 2 ||
                   sourceStack.Count == 0 ||
                   interpreter.IntegerStack.Top == interpreter.IntegerStack.ReverseElementAt(1);
        }

        protected override void InitState(IInterpreter interpreter, IStack<Expression> sourceStack)
        {
            this.body = sourceStack.Pop();
            this.destinationIndex = interpreter.IntegerStack.Pop();
            this.currentIndex = interpreter.IntegerStack.Top;
            this.incrementor = this.destinationIndex < this.currentIndex ? -1 : 1;
            this.currentIndex += this.incrementor;
        }
    }

    /// <summary>
    /// An iteration instruction that executes the top item on the CODE stack a number of times that depends on the
    /// top two integers, while also pushing the loop counter onto the INTEGER stack for possible access during the execution of
    /// the body of the loop. The top integer is the "destination index" and the second integer is the "current index." First the code
    /// and the integer arguments are saved locally and popped. Then the integers are compared. If the integers are equal then the current
    /// index is pushed onto the INTEGER stack and the code (which is the "body" of the loop) is pushed onto the EXEC stack for subsequent
    /// execution. If the integers are not equal then the current index will still be pushed onto the INTEGER stack but two items will be
    /// pushed onto the EXEC stack -- first a recursive call to CODE.DO*RANGE (with the same code and destination index, but with a current
    /// index that has been either incremented or decremented by 1 to be closer to the destination index) and then the body code. Note that
    /// the range is inclusive of both endpoints; a call with integer arguments 3 and 5 will cause its body to be executed 3 times, with the
    /// loop counter having the values 3, 4, and 5. Note also that one can specify a loop that "counts down" by providing a destination index
    /// that is less than the specified current index.
    /// </summary>
    [StatefullExpression]
    public class CodeDoRangeExpression : DoRangeExpression
    {
        public CodeDoRangeExpression() : base("CODE.DO*RANGE") { }

        public override void Eval(IInterpreter interpreter)
        {
            this.Eval(interpreter, interpreter.CodeStack);
        }
    }

    /// <summary>
    /// An iteration instruction that executes the top item on the EXEC stack a number of times that depends on the top two integers,
    /// while also pushing the loop counter onto the INTEGER stack for possible access during the execution of the body of the loop.
    /// This is similar to CODE.DO*COUNT except that it takes its code argument from the EXEC stack. The top integer is the
    /// "destination index" and the second integer is the "current index." First the code and the integer arguments are saved locally
    /// and popped. Then the integers are compared. If the integers are equal then the current index is pushed onto the INTEGER stack
    /// and the code (which is the "body" of the loop) is pushed onto the EXEC stack for subsequent execution. If the integers are not
    /// equal then the current index will still be pushed onto the INTEGER stack but two items will be pushed onto the EXEC stack
    /// -- first a recursive call to EXEC.DO*RANGE (with the same code and destination index, but with a current index that has been
    /// either incremented or decremented by 1 to be closer to the destination index) and then the body code. Note that the range is
    /// inclusive of both endpoints; a call with integer arguments 3 and 5 will cause its body to be executed 3 times, with the loop
    /// counter having the values 3, 4, and 5. Note also that one can specify a loop that "counts down" by providing a destination
    /// index that is less than the specified current index.
    /// </summary>
    [StatefullExpression]
    public class ExecDoRangeExpression : DoRangeExpression
    {
        public ExecDoRangeExpression() : base("EXEC.DO*RANGE") { }

        public override void Eval(IInterpreter interpreter)
        {
            this.Eval(interpreter, interpreter.ExecStack);
        }
    }
}