Vector of struct using and sorting

[gsk579]

My definition is
---------------------------------
using namespace std;

struct goodl { int line; string trl; };

struct vetor { goodl gline };

vector<vetor> goodlines;
-----------------------------------

I am not experienced with this topc and need help

I will use goodlines to store found lines in a text file
in the int I will store the line number form the file


I need to do two things that I don't how to

1) adding and reading data to from the vector
2) I need to sort the data in my vectior in
increasing line numbers (they can be mixed up)

Please advice

[keskiverto]

Why the vetor? It doesn't seem to add anything. You could as well have vector<goodl>.

See the std::sort. It has two versions. The first uses operator< of the elements. The second uses whatever binary predicate you give it.

Actually, you could replace the goodl with std::pair<int,string>. That already has operator<.

[gsk579]

Ohh, if it is declared as the pair you suggest then how to adress the items, if they are nameless?

[keskiverto]

They are not nameless. See http://www.cplusplus.com/reference/utility/pair/pair/

[Stewbond]

I wouldn't say that vetor doesn't add anything at all. Let's say that goodl is a very common struct used extensively throughout the application. You may not want to change it. Adding vetor gives us the opportunity to add a functor which will do our comparison for us:

struct goodl 
{ 
  int line; 
  string trl; 
}; 
struct vetor
{
  goodl gline;
  bool operator() (goodl left, goodl right) { return (left.line < right.line); }
};
std::vector<vetor> goodlines;
// Add data to goodlines
std::sort( goodlines.begin(), goodlines.end(), vetor() );

[gsk579]

Ohh I get a lot of compilation errors!

Should not the operator be specified with gline in stead of goodl?


Or am I lost?

[gsk579]

I finally got through the compilator with code structure

------------------------
pair <int, string> gdata;
vector<pair<int, string> > goodlines;
------------------------

To fetch data I used
---------------------
trl = goodlines[goodline].second;
------------------------

To sort i could simply write
...............................
sort(goodlines.begin(), goodlines.end());


And to push_back data
--------------------------
gdata.first = infLno; // a number
gdata.second = trline; // a string
goodlines.push_back(gdata);

[keskiverto]

#include <iostream>
#include <string>
#include <vector>
#include <utility>
#include <algorithm>

int main ()
{
  // If we can assume that no linenumber is negative, then unsigned
  std::vector<std::pair<unsigned int,std::string>> myvector;
  myvector.reserve(10);  // guess for final size; less reallocations

  // C++11 streamlined push_backs, could be in file-reading loop
  myvector.emplace_back( 3, "Hello" );
  myvector.emplace_back( 4, "world" );
  myvector.emplace_back( 1, "Dolly:" );
  myvector.emplace_back( 4, "again" );

  for (auto& x: myvector)
    std::cout << ' ' << x.first << ' ' << x.second;
  std::cout << '\n';

  std::sort( begin(myvector), end(myvector) );

  for (auto& x: myvector)
    std::cout << ' ' << x.first << ' ' << x.second;
  std::cout << '\n';

  return 0;
}