source: branches/2895_PushGP_GenealogyAnalysis/HeuristicLab.Problems.ProgramSynthesis/Push/Expressions/VectorLastExpressions.cs

using System.Collections.Generic;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;

namespace HeuristicLab.Problems.ProgramSynthesis {
  /// <summary>
  /// Gets the last item from the type stack
  /// </summary>
  /// <typeparam name="T"></typeparam>
  [StorableClass]
  public abstract class VectorLastExpression<T> : StatelessExpression {
    protected VectorLastExpression() { }
    [StorableConstructor]
    protected VectorLastExpression(bool deserializing) : base(deserializing) { }

    protected bool IsNoop(IPushStack<IReadOnlyList<T>> vectorStack) {
      return vectorStack.IsEmpty || vectorStack.Top.Count == 0;
    }

    protected void Eval(IPushStack<IReadOnlyList<T>> vectorStack, IPushStack<T> literalStack) {
      var vector = vectorStack.Pop();
      literalStack.Push(vector[vector.Count - 1]);
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.IntegerVector,
    "INTEGER[].LAST",
    "Gets the last item from the top INTEGER[].",
    StackTypes.Integer)]
  public class IntegerVectorLastExpression : VectorLastExpression<long> {
    public IntegerVectorLastExpression() { }
    [StorableConstructor]
    protected IntegerVectorLastExpression(bool deserializing) : base(deserializing) { }

    public override bool IsNoop(IInternalPushInterpreter interpreter) {
      return IsNoop(interpreter.IntegerVectorStack);
    }

    public override void Eval(IInternalPushInterpreter interpreter) {
      Eval(interpreter.IntegerVectorStack, interpreter.IntegerStack);
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.FloatVector,
    "FLOAT[].LAST",
    "Gets the last item from the top FLOAT[].",
    StackTypes.Float)]
  public class FloatVectorLastExpression : VectorLastExpression<double> {
    public FloatVectorLastExpression() { }
    [StorableConstructor]
    protected FloatVectorLastExpression(bool deserializing) : base(deserializing) { }

    public override bool IsNoop(IInternalPushInterpreter interpreter) {
      return IsNoop(interpreter.FloatVectorStack);
    }

    public override void Eval(IInternalPushInterpreter interpreter) {
      Eval(interpreter.FloatVectorStack, interpreter.FloatStack);
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.BooleanVector,
    "BOOLEAN[].LAST",
    "Gets the last item from the top BOOLEAN[].",
    StackTypes.Boolean)]
  public class BooleanVectorLastExpression : VectorLastExpression<bool> {
    public BooleanVectorLastExpression() { }
    [StorableConstructor]
    protected BooleanVectorLastExpression(bool deserializing) : base(deserializing) { }

    public override bool IsNoop(IInternalPushInterpreter interpreter) {
      return IsNoop(interpreter.BooleanVectorStack);
    }

    public override void Eval(IInternalPushInterpreter interpreter) {
      Eval(interpreter.BooleanVectorStack, interpreter.BooleanStack);
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.StringVector,
    "STRING[].LAST",
    "Gets the last item from the top STRING[].",
    StackTypes.String)]
  public class StringVectorLastExpression : VectorLastExpression<string> {
    public StringVectorLastExpression() { }
    [StorableConstructor]
    protected StringVectorLastExpression(bool deserializing) : base(deserializing) { }

    public override bool IsNoop(IInternalPushInterpreter interpreter) {
      return IsNoop(interpreter.StringVectorStack);
    }

    public override void Eval(IInternalPushInterpreter interpreter) {
      Eval(interpreter.StringVectorStack, interpreter.StringStack);
    }
  }
}