source: addons/HeuristicLab.PushGP/HeuristicLab.Problems.ProgramSynthesis/Push/Generators/CodeGenerator/LinearCodeGenerator.cs

using System.Collections.Generic;

namespace HeuristicLab.Problems.ProgramSynthesis.Push.Generators.CodeGenerator {
  using HeuristicLab.Core;
  using HeuristicLab.Problems.ProgramSynthesis.Push.Configuration;
  using HeuristicLab.Problems.ProgramSynthesis.Push.Data.Pool;
  using HeuristicLab.Problems.ProgramSynthesis.Push.Expressions;
  using HeuristicLab.Random;

  public class LinearCodeGenerator {
    public static PushProgram RandomProgram(IManagedPool<PushProgram> pool, IManagedPool<PooledList<Expression>> expressionListPool, int maxPoints, IRandom random = null, IReadOnlyPushConfiguration pushGpConfiguration = null, IDictionary<string, Expression> customExpressions = null) {
      var code = RandomCode(maxPoints, expressionListPool, random, pushGpConfiguration, customExpressions);

      return PushProgram.Create(pool, code);
    }

    public static PushProgram RandomProgram(IManagedPool<PooledList<Expression>> expressionListPool, int maxPoints, IRandom random = null, IReadOnlyPushConfiguration pushGpConfiguration = null, IDictionary<string, Expression> customExpressions = null) {
      var code = RandomCode(maxPoints, expressionListPool, random, pushGpConfiguration, customExpressions);

      return new PushProgram(code);
    }

    public static PushProgram RandomProgram(int maxPoints, IRandom random = null, IReadOnlyPushConfiguration pushGpConfiguration = null, IDictionary<string, Expression> customExpressions = null) {
      var code = RandomCode(maxPoints, null, random, pushGpConfiguration, customExpressions);

      return new PushProgram(code);
    }

    public static IReadOnlyList<Expression> RandomCode(
      int maxPoints,
      IManagedPool<PooledList<Expression>> expressionListPool = null,
      IRandom random = null,
      IReadOnlyPushConfiguration config = null,
      IDictionary<string, Expression> customExpressions = null) {
      if (maxPoints == 0)
        return new Expression[0];

      random = random ?? new MersenneTwister();
      config = config ?? new PushConfiguration();

      var size = maxPoints <= 1 ? 1 : random.Next(1, maxPoints);
      var expressions = expressionListPool == null ? new List<Expression>(size) : expressionListPool.Get();

      for (var i = 0; i < size; i++) {
        var expression = CodeGeneratorUtils.MapToExpression(
          random,
          config.ErcOptions,
          config,
          customExpressions);

        expressions.Add(expression);
      }

      return expressions;
    }


  }
}