Simple search engine using maps

Hi, for my last assignment I must make a program that takes in up to six files through the command line then print out the files in order of highest relavance depending on how many times the 2 keywords appear in each file. This is what I have so far but i'm getting a segmentation fault and I think it has something to do with the array of maps at line 24 but im not sure.

Code:

---

#include <fstream>
#include <iostream>
#include <string>
#include <map>

using namespace std;

int main(int argc, char* argv[])
{
  map<string, int> info[argc-1];
  string fileNames[argc-1];
  string word;
  string keyword = "key";
 
  for(int i=1; i < argc; i++)
  {
      fileNames[i] = argv[i];
    info[i] =  map<string, int>;
      ifstream fin(argv[i]);
      if(!fin) exit(1);
 
   
      while(!fin.eof())
      {
        fin>>word;

        if(info[i].count(word) <0 )
            info[i][word];
        else
            info[i][word]++;
      }   
  }


for(int i =0; i< info[i].size(); i++)
  for(map<string, int>::iterator x = info[i].begin(); x != info[i].end(); x++)
      cout<< x->first << ": "<< x->second << "\n";



}

---

array indexing starts at zero and goes to array-size - 1.

even when I put i-1 there I get an error: expected primary-expression before ";" token line 18

Quote:

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segmentation fault

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Quote:

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an error

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Okay, so which is it? Is the code you posted the code you really have?

Soma

It was a segmenation fault so I tried putting the code in red in but now I get error: expected primary-expression before ";" token line 18

Quote:

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map<string, int> info[argc-1];

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don't you need constant to declare array?
make it vector

while(!fin.eof()) - read FAQ why not to use eof with loops
should be

Code:

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while( fin>>word )

---

isnt argc a constant?

Well it's a variable.

You're getting a segfault because you're going out of bounds of your array.

Quote:

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make it vector

---

Agreed.

To visualise your problem, let's assume I passed in 2 file names, file.a and file.b ....

Code:

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for(int i = 1; i < argc; ++i)
    std::cout << "assigning fileNames[" << i << "] = " << argv[i] << "\n";
    fileNames[i] = argv[i];
}

---

Output:

Code:

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assigning fileNames[1] = file.a
assigning fileNames[2] = file.b <--- segfault, index out of bounds

---

Your array length is 2, in C++ array indexing begins at 0. So if you wish to access an index in your existing loop - you'll need to be i-1.

This is what I have using i-1 but I still get this error:
expected primary-expression before ";" token line 18

Code:

---

#include <fstream>
#include <iostream>
#include <string>
#include <map>

using namespace std;

int main(int argc, char* argv[])
{
  map<string, int> info[argc-1];
  string fileNames[argc-1];
  string word;
  string keyword = "key";
 
  for(int i=1; i < argc; i++)
  {
      fileNames[i-1] = argv[i];
      info[i-1] =  map<string, int>; //error here
      ifstream fin(argv[i]);
      if(!fin) exit(1);
 
   
      while(!fin.eof())
      {
        fin>>word;

        if(info[i-1].count(word) <0 )
            info[i-1][word];
        else
            info[i-1][word]++;
      }   
  }


for(int i =0; i< info[i].size(); i++)
  for(map<string, int>::iterator x = info[i].begin(); x != info[i].end(); x++)
      cout<< x->first << ": "<< x->second << "\n";



}

---

Never mind I just deleted the line and it works now but there is something odd that happens. When I put an even amount of text files in the program it produces a segmentation fault but when I put an odd number of files there is no error. for example:

./execProg word.txt - no error
./execProg word.txt word.txt - segmentation fault at end of output
./execProg word.txt word.txt word.txt - no error
./execProg word.txt word.txt word.txt word.txt - segmentation fault at end of output

Code:

---

#include <fstream>
#include <iostream>
#include <string>
#include <map>

using namespace std;

int main(int argc, char* argv[])
{
  map<string, int> info[argc-1];
  string fileNames[argc-1];
  string word;
  string keyword = "key";
 
  for(int i=1; i < argc; i++)
  {
      fileNames[i-1] = argv[i];
      ifstream fin(argv[i]);
      if(!fin) exit(1);
 
   
      while(!fin.eof())
      {
        fin>>word;

        if(info[i-1].count(word) <0 )
            info[i-1][word];
        else
            info[i-1][word]++;
      }   
  }


for(int i =0; i< info[i].size(); i++)
  for(map<string, int>::iterator x = info[i].begin(); x != info[i].end(); x++)
      cout<< x->first << ": "<< x->second << "\n";



}

---

variable length arrays are a compiler extension in C++, though it is so widely used (especially in old code) that I wouldn't imagine any compiler not implementing it (gcc accepts it without a warning even with -Wall).

>(gcc accepts it without a warning even with -Wall).

try -ansi -pedantic

I don't understand what you guys mean...^^^

Code:

---

map<string, int> info[argc-1];

---

The value of argc is not known to the compiler (it differs on each runtime), so it cannot create a usual, fixed-sized array. Instead your compiler as an extension allows you to create variable-sized arrays. Other compilers may not have that extension and your code may not be compilable for others.
It was suggested to use a vector:

Code:

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vector<map<string, int> > info(argc - 1);

---

Code:

---

while(!fin.eof())
      {
        fin>>word;

        if(info[i-1].count(word) <0 )
            info[i-1][word];
        else
            info[i-1][word]++;
      }

---

Firstly, read the FAQ about why you shouldn't control the input loop with eof() (this code has potential for "reading" the last word twice). The logic here about the map is a bit over-complicated too. I guess the if part is never executed (count of matches less than 0? especially if count()'s return type is unsigned?), so you might just remove the conditional thing.

Code:

---

for(int i =0; i< info[i].size(); i++)

---

This is probably causing your crashes. I can't see the relationship between the size of each dictionary and the total number of input files but that's what you are using to control the loop.

how about running the code in a debugger? it will tell you what line does your program segfault.

The error seems to have gone a away but i need some help finding a way to print out the filenames in order from highest relavance to least relevant. I was using a map but I doesnt work because sometimes the value can be the same for 2 files so it won't pring correctly. Heres the code I have now but what would be a good way to print the results? Thanks

Code:

---

/* Testing Files:
word.txt: computer server program computer internet internet website internet program program
word2.txt laptop website website computer internet email website server laptop
word3.txt (empty file)
(identical to word.txt)  word4.txt computer server program computer internet internet website internet program program
word5.txt email email email email email email email email
word6.txt server server server server server website website laptop email 
*/



#include <fstream>
#include <iostream>
#include <string>
#include <map>
#include <list>

using namespace std;

int main(int argc, char* argv[])
{
  map<string, int> info[argc-1];
  map<string, double> result;
  string fileNames[argc-1];
  list<double> value;
  string word;
  string keyword1;
  string keyword2;
 
  cout<<"Enter first keyword: ";
  cin >> keyword1;
  cout <<"Enter second keyword: ";
  cin >> keyword2;
  cout << "\n";

  for(int i=1; i < argc; i++)
  {
      fileNames[i-1] = argv[i];

      ifstream fin(argv[i]);
      if(!fin) exit(1);
 
   
    // while(!fin.eof())
        while(fin>>word)
        {
        // fin>>word;

        if(info[i-1].count(word) <0 )
            info[i-1][word];
        else
            info[i-1][word]++;
      }   
  }

  //This is where I need help
  for(int i=0; i < argc-1; i++)
  {
      value.push_back(info[i][keyword1]*.33 + info[i][keyword2]*.67);
      result[fileNames[i]] = (info[i][keyword1]*.33 + info[i][keyword2]*.67);
  }

  value.sort();
  cout << "Results (relevance from highest to lowest): \n";
 
  int i =0;
 
  for(int i=0; i < argc-1; i++)
  {
    i =0;
      while(true)
      {
        if(result[fileNames[i]] == value.back())
        { 
            cout<< fileNames[i] << ": " << value.back()<< "\n";
            result.erase(fileNames[i]);
            value.pop_back();
            break;
        }
        i++;
      }
  }


}

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If the value can be the same perhaps a multimap is more appropriate? (I didn't look at the code.)