source: addons/HeuristicLab.PushGP/HeuristicLab.Problems.ProgramSynthesis/Push/Expressions/DoTimesExpressions.cs

namespace HeuristicLab.Problems.ProgramSynthesis.Push.Expressions {
  using System;
  using Attributes;
  using Interpreter;
  using Persistence.Default.CompositeSerializers.Storable;
  using Stack;

  /// <summary>
  ///     Like CODE.DO*COUNT but does not push the loop counter.
  ///     This should be implemented as a macro that expands into CODE.DO*RANGE, similarly to the implementation
  ///     of CODE.DO*COUNT, except that a call to INTEGER.POP should be tacked on to the front of the loop body code
  ///     in the call to CODE.DO*RANGE.
  /// </summary>
  [Serializable]
  [StorableClass]
  [PushExpression(StackTypes.Code, "CODE.DO*TIMES", "Like CODE.DO*COUNT but does not push the loop counter", StackTypes.Integer)]
  public class CodeDoTimesExpression : StatelessExpression {
    public CodeDoTimesExpression() { }
    [StorableConstructor]
    protected CodeDoTimesExpression(bool deserializing) : base(deserializing) { }

    public override void Eval(IInternalPushInterpreter interpreter) {
      var destinationIndex = Math.Max(0, interpreter.IntegerStack.Top - 1);

      if (destinationIndex == 0) {
        interpreter.IntegerStack.Pop();
        interpreter.ExecStack.Push((PushProgram)interpreter.CodeStack.Pop());
        return;
      }

      interpreter.IntegerStack.Top = 0;
      interpreter.IntegerStack.Push(destinationIndex);

      var popExpressions = ExpressionTable.GetStatelessExpression<IntegerPopExpression>();
      PushProgram program;

      if (!interpreter.CodeStack.Top.IsProgram) {
        var expressions = interpreter.PoolContainer.ExpressionListPool.Get();
        expressions.Add(interpreter.ExecStack.Top);
        expressions.Add(popExpressions);

        program = PushProgram.Create(interpreter.PoolContainer.PushProgramPool, expressions);
      } else {
        program = PushProgram.Merge(
          interpreter.PoolContainer.PushProgramPool,
          interpreter.PoolContainer.ExpressionListPool,
          (PushProgram)interpreter.CodeStack.Top,
          popExpressions);
      }

      interpreter.CodeStack.Top = program;
      interpreter.ExecStack.Push(ExpressionTable.GetStatelessExpression<CodeDoRangeExpression>());
    }

    public override bool IsNoop(IInternalPushInterpreter interpreter) {
      return interpreter.IntegerStack.IsEmpty ||
             interpreter.IntegerStack.Top < 0 ||
             interpreter.CodeStack.IsEmpty;
    }
  }

  /// <summary>
  /// Like EXEC.DO*COUNT but does not push the loop counter. This should be implemented as a macro that expands into
  /// EXEC.DO*RANGE, similarly to the implementation of EXEC.DO*COUNT, except that a call to INTEGER.POP should be tacked on to the
  /// front of the loop body code in the call to EXEC.DO*RANGE. This call to INTEGER.POP will remove the loop counter, which will have
  /// been pushed by EXEC.DO*RANGE, prior to the execution of the loop body.
  /// </summary>
  [Serializable]
  [StorableClass]
  [PushExpression(StackTypes.Exec, "EXEC.DO*TIMES", "Like EXEC.DO*COUNT but does not push the loop counter", StackTypes.Integer, requiredBlockCount: 1)]
  public class ExecDoTimesExpression : StatelessExpression {
    public ExecDoTimesExpression() { }
    [StorableConstructor]
    protected ExecDoTimesExpression(bool deserializing) : base(deserializing) { }

    public override void Eval(IInternalPushInterpreter interpreter) {
      var destinationIndex = Math.Max(0, interpreter.IntegerStack.Top - 1);

      if (destinationIndex == 0) {
        interpreter.IntegerStack.Pop();
        return;
      }

      interpreter.IntegerStack.Top = 0;
      interpreter.IntegerStack.Push(destinationIndex);

      var popExpressions = ExpressionTable.GetStatelessExpression<IntegerPopExpression>();
      PushProgram program;

      if (!interpreter.ExecStack.Top.IsProgram) {
        var expressions = interpreter.PoolContainer.ExpressionListPool.Get();
        expressions.Add(interpreter.ExecStack.Top);
        expressions.Add(popExpressions);

        program = PushProgram.Create(interpreter.PoolContainer.PushProgramPool, expressions);
      } else {
        program = PushProgram.Merge(
          interpreter.PoolContainer.PushProgramPool,
          interpreter.PoolContainer.ExpressionListPool,
          (PushProgram)interpreter.ExecStack.Top,
          popExpressions);
      }

      interpreter.ExecStack.Top = program;
      interpreter.ExecStack.Push(ExpressionTable.GetStatelessExpression<ExecDoRangeExpression>());
    }

    public override bool IsNoop(IInternalPushInterpreter interpreter) {
      return interpreter.IntegerStack.IsEmpty ||
             interpreter.IntegerStack.Top < 0 ||
             interpreter.ExecStack.IsEmpty;
    }
  }
}