c++ - 未声明的标识符？

Question

不断出现代码错误，这是从旧 VS 到 2010 版本的转换:

#include <string>
#include <stdlib.h>
#include <iostream>
#include <time.h>
#include <math.h>

using std::string;

#define CROSSOVER_RATE            0.7
#define MUTATION_RATE             0.001
#define POP_SIZE                  100           //must be an even number
#define CHROMO_LENGTH             300
#define GENE_LENGTH               4
#define MAX_ALLOWABLE_GENERATIONS   400

//returns a float between 0 & 1
#define RANDOM_NUM      ((float)rand()/(RAND_MAX+1))

//----------------------------------------------------------------------------------------
//
//  define a data structure which will define a chromosome
//
//----------------------------------------------------------------------------------------
struct chromo_typ
{
    //the binary bit string is held in a std::string
  string    bits;  

    float     fitness;

    chromo_typ(): bits(""), fitness(0.0f){};
    chromo_typ(string bts, float ftns): bits(bts), fitness(ftns){}
};


/////////////////////////////////prototypes/////////////////////////////////////////////////////

void    PrintGeneSymbol(int val);
string  GetRandomBits(int length);
int     BinToDec(string bits);
float   AssignFitness(string bits, int target_value);
void    PrintChromo(string bits);
void    PrintGeneSymbol(int val);
int     ParseBits(string bits, int* buffer);
string  Roulette(int total_fitness, chromo_typ* Population);
void    Mutate(string &bits);
void    Crossover(string &offspring1, string &offspring2);



//-------------------------------main--------------------------------------------------
//
//-------------------------------------------------------------------------------------
int main()
{
    //seed the random number generator
    srand((int)time(NULL));

  //just loop endlessly until user gets bored :0)
  while (true)
  {
    //storage for our population of chromosomes.
    chromo_typ Population[POP_SIZE];

      //get a target number from the user. (no error checking)
      float Target;
      cout << "\nInput a target number: ";
      cin >> Target;
    cout << endl << endl;

      //first create a random population, all with zero fitness.
      for (int i=0; i<POP_SIZE; i++)
      {
          Population[i].bits      = GetRandomBits(CHROMO_LENGTH);
          Population[i].fitness = 0.0f;
      }

      int GenerationsRequiredToFindASolution = 0;

      //we will set this flag if a solution has been found
      bool bFound = false;

      //enter the main GA loop
      while(!bFound)
      {
          //this is used during roulette wheel sampling
          float TotalFitness = 0.0f;

          // test and update the fitness of every chromosome in the 
      // population
          for (int i=0; i<POP_SIZE; i++)
          {
              Population[i].fitness = AssignFitness(Population[i].bits, Target);

              TotalFitness += Population[i].fitness;
          }

          // check to see if we have found any solutions (fitness will be 999)
          for (i=0; i<POP_SIZE; i++)
          {
              if (Population[i].fitness == 999.0f)
              {
          cout << "\nSolution found in " << GenerationsRequiredToFindASolution << " generations!" << endl << endl;;

                  PrintChromo(Population[i].bits);

                  bFound = true;

          break;
              }
          }

          // create a new population by selecting two parents at a time and creating offspring
      // by applying crossover and mutation. Do this until the desired number of offspring
      // have been created. 

          //define some temporary storage for the new population we are about to create
          chromo_typ temp[POP_SIZE];

          int cPop = 0;

          //loop until we have created POP_SIZE new chromosomes
          while (cPop < POP_SIZE)
          {
              // we are going to create the new population by grabbing members of the old population
              // two at a time via roulette wheel selection.
              string offspring1 = Roulette(TotalFitness, Population);
              string offspring2 = Roulette(TotalFitness, Population);

        //add crossover dependent on the crossover rate
        Crossover(offspring1, offspring2);

              //now mutate dependent on the mutation rate
              Mutate(offspring1);
              Mutate(offspring2);

              //add these offspring to the new population. (assigning zero as their
        //fitness scores)
              temp[cPop++] = chromo_typ(offspring1, 0.0f);
              temp[cPop++] = chromo_typ(offspring2, 0.0f);

          }//end loop

          //copy temp population into main population array
          for (i=0; i<POP_SIZE; i++)
      {
              Population[i] = temp[i];
      }

          ++GenerationsRequiredToFindASolution;

          // exit app if no solution found within the maximum allowable number
          // of generations
          if (GenerationsRequiredToFindASolution > MAX_ALLOWABLE_GENERATIONS)
          {
              cout << "No solutions found this run!";

              bFound = true;
          }

      }

    cout << "\n\n\n";

  }//end while

    return 0;
}




//---------------------------------GetRandomBits-----------------------------------------
//
//  This function returns a string of random 1s and 0s of the desired length.
//
//-----------------------------------------------------------------------------------------
string  GetRandomBits(int length)
{
    string bits;

    for (int i=0; i<length; i++)
    {
        if (RANDOM_NUM > 0.5f)

            bits += "1";

        else

            bits += "0";
    }

    return bits;
}

//---------------------------------BinToDec-----------------------------------------
//
//  converts a binary string into a decimal integer
//
//-----------------------------------------------------------------------------------
int BinToDec(string bits)
{
    int val          = 0;
    int value_to_add = 1;

    for (int i = bits.length(); i > 0; i--)
    {


        if (bits.at(i-1) == '1')

            val += value_to_add;

        value_to_add *= 2;

    }//next bit

    return val;
}


//---------------------------------ParseBits------------------------------------------
//
// Given a chromosome this function will step through the genes one at a time and insert 
// the decimal values of each gene (which follow the operator -> number -> operator rule)
// into a buffer. Returns the number of elements in the buffer.
//------------------------------------------------------------------------------------
int ParseBits(string bits, int* buffer)
{

    //counter for buffer position
    int cBuff = 0;

    // step through bits a gene at a time until end and store decimal values
    // of valid operators and numbers. Don't forget we are looking for operator - 
    // number - operator - number and so on... We ignore the unused genes 1111
    // and 1110

    //flag to determine if we are looking for an operator or a number
    bool bOperator = true;

    //storage for decimal value of currently tested gene
    int this_gene = 0;

    for (int i=0; i<CHROMO_LENGTH; i+=GENE_LENGTH)
    {
        //convert the current gene to decimal
        this_gene = BinToDec(bits.substr(i, GENE_LENGTH));

        //find a gene which represents an operator
        if (bOperator)
        {
            if ( (this_gene < 10) || (this_gene > 13) ) 

                continue;

            else
            {
                bOperator       = false;
                buffer[cBuff++] = this_gene;
                continue;
            }
        }

        //find a gene which represents a number
        else
        {
            if (this_gene > 9)

                continue;

            else
            {
                bOperator       = true;
                buffer[cBuff++] = this_gene;
                continue;
            }
        }

    }//next gene

    //  now we have to run through buffer to see if a possible divide by zero
    //  is included and delete it. (ie a '/' followed by a '0'). We take an easy
    //  way out here and just change the '/' to a '+'. This will not effect the 
    //  evolution of the solution
    for (i=0; i<cBuff; i++)
    {
        if ( (buffer[i] == 13) && (buffer[i+1] == 0) )

            buffer[i] = 10;
    }

    return cBuff;
}

//---------------------------------AssignFitness--------------------------------------
//
//  given a string of bits and a target value this function will calculate its  
//  representation and return a fitness score accordingly
//------------------------------------------------------------------------------------
float AssignFitness(string bits, int target_value)
{

    //holds decimal values of gene sequence
    int buffer[(int)(CHROMO_LENGTH / GENE_LENGTH)];

    int num_elements = ParseBits(bits, buffer);

    // ok, we have a buffer filled with valid values of: operator - number - operator - number..
    // now we calculate what this represents.
    float result = 0.0f;

    for (int i=0; i < num_elements-1; i+=2)
    {
        switch (buffer[i])
        {
            case 10:

                result += buffer[i+1];
                break;

            case 11:

                result -= buffer[i+1];
                break;

            case 12:

                result *= buffer[i+1];
                break;

            case 13:

                result /= buffer[i+1];
                break;

        }//end switch

    }

    // Now we calculate the fitness. First check to see if a solution has been found
    // and assign an arbitarily high fitness score if this is so.

    if (result == (float)target_value)

        return 999.0f;

    else

        return 1/(float)fabs((double)(target_value - result));
    //  return result;
}

//---------------------------------PrintChromo---------------------------------------
//
// decodes and prints a chromo to screen
//-----------------------------------------------------------------------------------
void PrintChromo(string bits)
{   
    //holds decimal values of gene sequence
    int buffer[(int)(CHROMO_LENGTH / GENE_LENGTH)];

    //parse the bit string
    int num_elements = ParseBits(bits, buffer);

    for (int i=0; i<num_elements; i++)
  {
        PrintGeneSymbol(buffer[i]);
  }

    return;
}

//--------------------------------------PrintGeneSymbol-----------------------------
//  
//  given an integer this function outputs its symbol to the screen 
//----------------------------------------------------------------------------------
void PrintGeneSymbol(int val)
{
    if (val < 10 )

        cout << val << " ";

    else
    {
        switch (val)
        {

        case 10:

            cout << "+";
            break;

        case 11:

            cout << "-";
            break;

        case 12:

            cout << "*";
            break;

        case 13:

            cout << "/";
            break;

        }//end switch

        cout << " ";
    }

    return;
}

//------------------------------------Mutate---------------------------------------
//
//  Mutates a chromosome's bits dependent on the MUTATION_RATE
//-------------------------------------------------------------------------------------
void Mutate(string &bits)
{
    for (int i=0; i<bits.length(); i++)
    {
        if (RANDOM_NUM < MUTATION_RATE)
        {
            if (bits.at(i) == '1')

                bits.at(i) = '0';

            else

                bits.at(i) = '1';
        }
    }

    return;
}

//---------------------------------- Crossover ---------------------------------------
//
//  Dependent on the CROSSOVER_RATE this function selects a random point along the 
//  lenghth of the chromosomes and swaps all the  bits after that point.
//------------------------------------------------------------------------------------
void Crossover(string &offspring1, string &offspring2)
{
  //dependent on the crossover rate
  if (RANDOM_NUM < CROSSOVER_RATE)
  {
    //create a random crossover point
    int crossover = (int) (RANDOM_NUM * CHROMO_LENGTH);

    string t1 = offspring1.substr(0, crossover) + offspring2.substr(crossover, CHROMO_LENGTH);
    string t2 = offspring2.substr(0, crossover) + offspring1.substr(crossover, CHROMO_LENGTH);

    offspring1 = t1; offspring2 = t2;                 
  }
}


//--------------------------------Roulette-------------------------------------------
//
//  selects a chromosome from the population via roulette wheel selection
//------------------------------------------------------------------------------------
string Roulette(int total_fitness, chromo_typ* Population)
{
    //generate a random number between 0 & total fitness count
    float Slice = (float)(RANDOM_NUM * total_fitness);

    //go through the chromosones adding up the fitness so far
    float FitnessSoFar = 0.0f;

    for (int i=0; i<POP_SIZE; i++)
    {
        FitnessSoFar += Population[i].fitness;

        //if the fitness so far > random number return the chromo at this point
        if (FitnessSoFar >= Slice)

            return Population[i].bits;
    }

    return "";
}   

我得到的错误是:

error C2065: 'cin' : undeclared identifier
error C2065: 'cout' : undeclared identifier
error C2065: 'endl' : undeclared identifier
error C2065: 'i' : undeclared identifier
error C2228: left of '.bits' must have class/struct/union
error C2228: left of '.fitness' must have class/struct/union

Answer 1

您要么想要 std::cin(等)，要么在源文件顶部使用 using std::cin;。

至于i的问题；好吧，你有一个使用 i 而不声明它的循环(这反过来也导致了 .bits 和 .fitness 的问题.