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

using System.Collections.Generic;

namespace HeuristicLab.Problems.ProgramSynthesis.Push.Expressions {
  using System;
  using System.Linq;

  using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
  using HeuristicLab.Problems.ProgramSynthesis.Push.Attributes;
  using HeuristicLab.Problems.ProgramSynthesis.Push.Extensions;
  using HeuristicLab.Problems.ProgramSynthesis.Push.Interpreter;
  using HeuristicLab.Problems.ProgramSynthesis.Push.Stack;

  /// <summary>
  /// Takes the first N items from the type stack, where N is from the integer stack
  /// </summary>
  /// <typeparam name="T"></typeparam>
  [StorableClass]
  public abstract class VectorTakeExpression<T> : StatelessExpression {
    protected VectorTakeExpression() { }
    [StorableConstructor]
    protected VectorTakeExpression(bool deserializing) : base(deserializing) { }

    protected bool IsNoop(IInternalPushInterpreter interpreter, IPushStack<IReadOnlyList<T>> vectorStack) {
      return vectorStack.IsEmpty || interpreter.IntegerStack.IsEmpty;
    }

    protected void Eval(IInternalPushInterpreter interpreter, IPushStack<IReadOnlyList<T>> vectorStack) {

      if (vectorStack.Top.Count == 0)
        return;

      var count = interpreter.IntegerStack.Pop().AsInt(vectorStack.Top.Count);

      if (count < 0)
        count *= -1;

      var vector = vectorStack.Top;
      var list = vector as List<T>;

      if (list != null) {
        var newTop = new T[count];
        list.CopyTo(0, newTop, 0, count);
        vectorStack.Top = newTop;
        return;
      }

      var array = vector as T[];
      if (array != null) {
        var newTop = new T[count];
        Array.Copy(array, 0, newTop, 0, count);
        vectorStack.Top = newTop;
        return;
      }

      vectorStack.Top = vector.Take(count).ToList();
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.IntegerVector,
    "INTEGER[].TAKE",
    "Takes the first n items of the top INTEGER[], where n is from the INTEGER stack.",
    StackTypes.Integer)]
  public class IntegerVectorTakeExpression : VectorTakeExpression<long> {
    public IntegerVectorTakeExpression() { }
    [StorableConstructor]
    protected IntegerVectorTakeExpression(bool deserializing) : base(deserializing) { }

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

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

  [StorableClass]
  [PushExpression(
    StackTypes.FloatVector,
    "FLOAT[].TAKE",
    "Takes the first n items of the top FLOAT[], where n is from the INTEGER stack.",
    StackTypes.Integer)]
  public class FloatVectorTakeExpression : VectorTakeExpression<double> {
    public FloatVectorTakeExpression() { }
    [StorableConstructor]
    protected FloatVectorTakeExpression(bool deserializing) : base(deserializing) { }

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

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

  [StorableClass]
  [PushExpression(
    StackTypes.BooleanVector,
    "BOOLEAN[].TAKE",
    "Takes the first n items of the top BOOLEAN[], where n is from the INTEGER stack.",
    StackTypes.Integer)]
  public class BooleanVectorTakeExpression : VectorTakeExpression<bool> {
    public BooleanVectorTakeExpression() { }
    [StorableConstructor]
    protected BooleanVectorTakeExpression(bool deserializing) : base(deserializing) { }

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

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

  [StorableClass]
  [PushExpression(
    StackTypes.StringVector,
    "STRING[].TAKE",
    "Takes the first n items of the top STRING[], where n is from the INTEGER stack.",
    StackTypes.Integer)]
  public class StringVectorTakeExpression : VectorTakeExpression<string> {
    public StringVectorTakeExpression() { }
    [StorableConstructor]
    protected StringVectorTakeExpression(bool deserializing) : base(deserializing) { }

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

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