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I've spent the whole day trying to figure out why this doesn't want to work, I'm extracting information from a text file and sending the values through as arrays to a constructor (which works fine, I can print out the values and they will display.) But I can't create an object of another class inside of the constructor without it going into an infinite loop.

My main File:

int main(int argc, char** argv)
{
string line;
ifstream myfile ("test1.txt");
string rows [15];
int index = 0;

string tempForSize[5];
double * sizeArray = new double[5]; 
int firstIntOccur =0; 

string * arrForEquations = new string[12];
int equationCount = 0;

if (myfile.is_open())       {
    while ( myfile.good() )     {
        getline (myfile,line);
        rows[index] =line;
        index++;
    }
    myfile.close();
}
else 
    cout << "Unable to open file" << endl; 

for(int i=0; i <12;i++)     {
    if(rows[i].find("EQUATIONS: ")!=string::npos)       { 
        i++;
        i++;
        while(i <index) { 
            arrForEquations[equationCount]=rows[i];
            equationCount++;
            i++;
        }
        break;
    }

    if(rows[i].find(':')!=string::npos)     {
        firstIntOccur =rows[i].find(':');
        tempForSize[i].assign(rows[i],firstIntOccur+2,rows[i].size());
    }
}

for(int  i =0;i <5; i++)        {  
    sizeArray[i] = atof(tempForSize[i].c_str());
}
try
{
    string * equations = arrForEquations;
    GeneticAlgorithm a(sizeArray, equations, equationCount);
}
catch(string s)
{
    cout << s << endl;
}

return 0;

 }

The constructor of the GeneticAlgorithm Class:

GeneticAlgorithm::GeneticAlgorithm(double *& arr, string * sArr, int size)      {
Equation ** e = new Equation*[size];
for(int i = 0; i < size; i++)   {
    e[i] = new Equation(sArr[i]);
}
}

The equation class works perfectly when strings are entered into it, I just can't figure out why this does not want to work.

Thanks in advance.

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3
  • 2
    Vectors will save you time and headaches. Use them for dynamic allocation when possible. Commented Nov 2, 2012 at 21:58
  • Try to prepare a code sample which compiles and reproduces your error. Too much information here. Commented Nov 2, 2012 at 21:59
  • No can I. There's no reason for the posted code to go into an infinite loop. Please post compilable code that reproduces the bug. Commented Nov 2, 2012 at 22:26

2 Answers 2

Reset to default
2

Quick note which does not answer your question but I still was compelled to point out. Avoid using pointers. 

// Instead of using 'string * equations = new string[12]'
std::vector<std::string> equations;

// Instead of using 'double * sizeArray = new double[5]'
std::vector<double> sizeArray;

Use STL wherever you can. They are provided to make your life easy and the code looks less cryptic.

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3 Comments

Or, if you need to use pointers (use cases do exist, to avoid copies at push_back, whatever), use a smart pointer (i.e., unique_ptr<T>)., This also does not answer the question. "Don't use pointers" doesn't help the OP understand anything. It's hard to understand why RAII style containers and more modern approaches to memory management are beneficial if you don't first experience the pains associated with the alternative.
I understand and thank for explicitly stating that. One thing that I have seen very often is the inadequate use of STL containers in cases where they seem highly useful, like the case above :) Of course, I love pointers but that is after writing lots of pointer code and scratching my head (cursing them).
Agreed 100%. I see vector<T>* v; and/or vector<T*> all of the time and it is a shame, but there's a reason you see things like this; the person writing the code doesn't really understand the problem they are trying to solve. Yours is a great suggestion, I only think that understanding should come before one delves into more sophisticated approaches. It's difficult to understand why vector<T*> is wrong before you really have memory management down pat and before you get bitten in the @ss a few times by bugs related to manual memory management.
1

This isn't really an answer to your question, but it will point out a lot of other mistakes, and once they've been cleaned up, it may become possible to understand what is actually taking place.

The first problem is that there is no functional decomposition. The function is just too big, and should be cut into several smaller functions. In general (and there are some notable exceptions), if a function is longer than about eight or ten lines, it needs refactoring.

On to more detailed problems: there are too many magic numbers, and for the most part, they are wrong. Your user will not input exactly 15 lines. He will input 5, or 500 or who knows. (If, of course, he enters 500, you've got a big problem.) The simplest and most common way of handling this is to use std::vector and its push_back member function. This isn't perfect (what happens if your user enters 5 trillion lines, or 1 line with 5 trillion characters), but for most appilications, it's good enough.

More generally, this applies to pretty much all of your arrays. Just use std::vector, and let them grow as needed, rather than using a magic constant for the size. And why on earth:

string tempForSize[5];
double * sizeArray = new double[5];

Why dynamic allocation in one case, and not in the other? (For that matter, you don't need tempForSize anyway. Once you've got the string value in a local temporary, you can convert it immediately and put it into the sizeArray.)

The loop while ( myfile.good() ) is never really correct. And you use the line read by getline without testing whether the read succeede or not. The correct way to do something like this is:

std::vector<std::string>
readRows( std::istream& source )
{
    std::vector<std::string> results;
    std::string line;
    while ( std::getline( source, line ) ) {
        result.push_back( line );
    }
    return results;
}

Rewrite the code using standard best practices, so that we can see what is actually going on, and we aren't distracted by so many other problems, and if you still have problems, then ask again.

(BYW: where on earth do people get the idea to loop on file.good(). It comes up over; if there's some textbook showing it, then we really have to act in some way to get it taken out of circulation.)

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2 Comments

Feel bad for the guy. Nobody is helping him with his problems but throwing in a whole lot of advise. That's my dad :)
@James Kanze I understand what you mean by everything, the thing is for this project we will always be given an input file with 15 lines. I know I'm not using the best practices its just that these aren't my problems and I will probably look back on all these things later, my problem is that I can print out the numbers in the arrForEquations array but I can't pass them to a function that accepts a string. I'm scared of changing all of the code for now with it still having the same problem though.

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