Thread: getline??? how do I use something like it for an integer

Code:

#include <fstream.h> //header for cout and cin
#include <string.h> // header for strings
#include <windows.h> // required for system("cls")

struct chem
{
	char symbol[2];
	char name[25];
	int numb;
	long mass;
}

main()
{
	ifstream infile;

	int i = 0;

	char dummybuffer[25];
	
	chem element[112];

	infile.open("CHEM.DAT",ios::in);

	for (i=0; !infile.eof(); i++)
	{
		infile.getline(element[i].symbol, 256, ','||'\n');	//get data until new line
		infile.getline(element[i].name, 256, ','||'\n');	
		infile >> dummybuffer;
		element[i].numb = atoi(dummybuffer);
		infile >> dummybuffer;
		element[i].mass = atoi(dummybuffer);
//		infile.getline(element[i].numb, 256, ','||'\n');	
//		infile.getline(element[i].mass, 256, ','||'\n');	

	}

	infile.close();

	cout << element[0].symbol;

	return 0;
}

Those commented out getlines won't work because the struct type is wrong.

The non commented version would probably work, but I need it to stop as soon as it gets to a comma.

How might I do this?

Thanks.

Try looking at this, see if these can explkain it:

http://cboard.cprogramming.com/searc...der=descending


If not...I'm sure soeone will be happy to show you.

You have a string in a file, then you want to convert it to an int?
First, read it into a temporary buffer, then use atoi() or strtol() to convert the string to an int.

Read the line to a string, then parse the type from a stringstream.
This is one suggestion, not compiled, but should work.

Code:

#include <sstream>
#include <iostream>
#include <string>
#include <theheadersialwaysforget>

class  __get
{
  bool Success;
} get;
template<typename T>
T operator= (T& value, __get g)
{
  string s;
  getline(cin,s);
  istringstream sin(s);
  g.Success = sin >> value;
}

...

int main()
{
  //Example of usage:
  int a,b;
  a = get;
  if (get.Success)
  {
    b = get;
  }
}

Code:

#include <fstream.h> //header for cout and cin
#include <string.h> // header for strings
#include <windows.h> // required for system("cls")

struct chem
{
	char symbol[2];
	char name[25];
	int numb;
	long mass;
};

main()
{
	ifstream infile;

	int i = 0;

	char dummybuffer[25];
	
	chem element[112];

	infile.open("CHEM.DAT",ios::in);

	for (i=0; !infile.eof(); i++)
	{
		infile.getline(element[i].symbol, 256, ','||'\n');	//get data until new line
		infile.getline(element[i].name, 256, ','||'\n');	
		infile.getline(dummybuffer, 256, ','||'\n');	
		element[i].numb = atoi(dummybuffer);
		infile.getline(dummybuffer, 256, ','||'\n');	
		element[i].mass = atoi(dummybuffer);
	}

	infile.close();

	cout << element[0].symbol;

	return 0;
}

That doesn't seem to want to cout anything... any ideas?

CHEM.DAT looks like this:

Ne,Neon,11,11.1
H,Hydrogen,1,1.001

the numbers there aren't right, I didn't cut and paste it. And it goes in order.

it works for me...
oh and a couple of notes
you might want to shorten these

Code:

infile.getline(element[i].symbol, 256, ','||'\n');
infile.getline(element[i].name, 256, ','||'\n');

to these

Code:

infile.getline(element[i].symbol, 2, ','||'\n');
infile.getline(element[i].name, 25, ','||'\n');

in order to avoid buffer overruns...


and did you ever check if you actually opened the file successfully?
do something like

Code:

if(!infile)
{
    cout << "Error! could not load CHEM.DAT";
    return 1;
}

right after your infile.open statement.


(edit)
oh and one other thing... don't you want to use floats instead of ints for your weight variables?
and use the atof() function I think it is, rather than atoi().
Cause if you use int you will lose whatever is after the decimal point..
(/edit)

>>infile.getline(dummybuffer, 256, ','||'\n');
The last parameter to getline is a char, I don't believe you can OR two together, especially with a logical OR.

>>char symbol[2];
If the symbol is 2 characters long, you should have an array sized 3.

>This is one suggestion, not compiled, but should work.
I hope it doesn't, overloaded assignment operators must be member functions. This is also overcomplicating things just a bit, why not just use a template function which returns the correct value and throws an exception otherwise? One possible implementation would be:

Code:

#include <stdexcept>
#include <iostream>
#include <sstream>
#include <string>

template <typename T>
T string_cast ( std::string& s )
{
  T value;

  std::istringstream sin ( s );
  sin>> value;

  if ( !sin )
    throw std::invalid_argument ( "Value must be an integer" );

  return value;
}

int main()
{
  int a;
  std::string s = "12345";

  try {
    a = string_cast<int> ( s );

    std::cout<< a <<std::endl;
  }
  catch ( std::invalid_argument& ia ) {
    std::cerr<< ia.what();
  }

  std::cin.get();
}

-Prelude

Originally posted by Prelude
>-Prelude

Ok... first of all, I'm NEVER going to use

using namespace std;

unless someone explains exactly what it does and how they're using it.
If I just used your code, then I'd never get any better, I'd still have the same kind of problem

Second, it DOESN'T work for me, I can't cout it at all.

Ok... first of all, I'm NEVER going to use

using namespace std;

unless someone explains exactly what it does and how they're using it.

I'm thoroughly confused. Is this addressed to me? I can't tell because none of my code opens the std namespace completely and I've never recommended it.

>If I just used your code, then I'd never get any better, I'd still have the same kind of problem
Once again I'm confused. My reply was to Sang-drax and his suggestion.

>Second, it DOESN'T work for me, I can't cout it at all.
What doesn't work? Can you be more specific?

This is a very incoherent post, you apparently address me and then talk about topics that I haven't introduced or even mentioned in this thread.

-Prelude

>sorry about that... std::istringstream sin ( s ); to me is using namespace std... shows how little I know
Rest assured that if I recommend polluting the global namespace, everyone will expect me to give a very good reason for it.

-Prelude

All right, I figured out the problem without figuring it out...

if I use

infile.getline(dummybuffer, 2, ','||'\n'); //get data until new line
cout << dummybuffer;

it couts it just fine.

But if I use

infile.getline(element[i].symbol, 2, ','||'\n'); //get data until new line
cout << element[i].symbol;

then it won't work... so its something about my struct... any ideas?

(edit)
Oh, and by the way

strcpy(element[0].symbol,"Ne");
cout << element[0].symbol;

works just fine. It outputs "Ne"

>infile.getline(element[i].symbol, 2, ','||'\n'); //get data until new line

//Should be:
infile.getline(element[i].symbol, 3, ','||'\n'); //get data until new line

And as pointed out earlier:
> char symbol[2];
//To store two characters, you need 3 elements (one for the string terminator)
char symbol[3];