C / C++ / MFC

25-Apr-06 13:44

You guys have been a big help with my previous question, I have another.

I have input file "input.txt"
i have outputfile "output.txt"

input.txt will always look like
A 1 5 4
B 2 6 3

the first value can be a different, but will always be one char in length.

I want to grab each value on the first and second line and assign variables to them.

i've looked a lot about inFile.get or .getline or .peek, but it's not making a whole lot of sense.

I have this:

ifstream inf;
ofstream outf1;
ofstream outf2;

inf.open(argv[1], ios::in);
outf1.open(argv[2], ios::in);
outf2.open(argv[2], ios::out);

char n, x, y, z;
while(!inf.eof())
inf.get >> n >> x >> y >> z;

Can anyone shed any light?

Thanks,
Ed

Stephen Hewitt25-Apr-06 13:52

25-Apr-06 13:52

Reading a char doesn't skip white space and you don't need the get. Try this:

inf >> n >> ws >> x  >> ws >> y  >> ws >> z  >> ws;

The ws manipulator can be used to explicitly skip white space.

Steve

etm12425-Apr-06 13:56

25-Apr-06 13:56

i tried something like that, but i get this error:

error C2475: 'std::basic_istream<_Elem,_Traits>::get' : forming a pointer-to-member requires explicit use of the address-of operator ('&') and a qualified name
with
[
_Elem=char,
_Traits=std::char_traits<char>
]
error C2475: 'std::basic_istream<_Elem,_Traits>::get' : forming a pointer-to-member requires explicit use of the address-of operator ('&') and a qualified name
with
[
_Elem=char,
_Traits=std::char_traits<char>
]
warning C4552: '>>' : operator has no effect; expected operator with side-effect

Stephen Hewitt25-Apr-06 14:05

25-Apr-06 14:05

I was wrong about the fact that reading a char doesn't skip white space. I used the following test program and was able to read in data like yours however:
-----
// Console.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <fstream>
#include <iostream>
using namespace std;

int main(int argc, char* argv[])
{
ifstream in("C:\\a.txt");
char n, a, b, c;
while (in >> n >> a >> b >> c)
{
cout << n << " " << a << " " << b << " " << c << endl;
}

return 0;
}

Steve

etm12425-Apr-06 14:09

25-Apr-06 14:09

worked like a charm, Steve.

Thank you!

etm12425-Apr-06 14:13

25-Apr-06 14:13

Steve, one last quick one, if I have two lines, how would I handle that?

my input file reads:

A 1 2 3
B 4 5 6

Stephen Hewitt25-Apr-06 14:20

25-Apr-06 14:20

It should work with multiple lines. It will work with or without multiple lines. If reads the 1st character into n and the 2d, 3rd and 4th into a, b, c, respectively. Then it repeats the process. What exactly do you want to do with the data?

Steve

etm12425-Apr-06 14:22

25-Apr-06 14:22

i came up with this...
char n, x, y, z, n2, x2, y2, z2;
while(!inf.eof())
inf >> n >> x >> y >> z >> n2 >> x2 >> y2 >> z2;

but was just seeing if there was a more efficient way of grabbing it.

in the large scheme of things, I am reading in this values:

A 1 5 7
B 2 4 5

which are actually points on a grid. so they are A(1,5,7) and B(2,4,5). Now I use those values and plug them into my class to do calculations. I never really worked with the ifstream much and i thank you again for your assistance!

-Ed

Stephen Hewitt25-Apr-06 14:26

25-Apr-06 14:26

Can you show the code which plugs the data into your class?

Steve

etm12425-Apr-06 14:28

25-Apr-06 14:28

im messing with that right now, but I can show you what I have so far...

int main(int argc, char* argv[])
{

ifstream inf;
ofstream outf1;
ofstream outf2;

inf.open("input.txt", ios::in);
outf1.open("output.txt", ios::in);
outf1.close();
outf2.open("output.txt", ios::out);

char n, x, y, z, n2, x2, y2, z2;
while(!inf.eof())
inf >> n >> x >> y >> z >> n2 >> x2 >> y2 >> z2;

Point p0;
Point p1(x,y,n);
Point3D p1(z);
p1.printP();

Point p2(x2,y2,n2);
Point3D p2(z3);
p2.printP();

system("pause");

/* inf.close();
outf2.close();
return 0;*/

}

I am working on a piece that exhibits inheritance. Basically Point class is already defined. I am inheriting it into Point3D class. I am getting my values from the input file, computing the distance between the points, then outputing to an output file.

etm12425-Apr-06 14:36

25-Apr-06 14:36

I obviously can't pass char into my functions, i need to convert my input variables into integers. I was playing around with the int function, but I think that is giving me the ascii value. How can I make

char "1" = int 1

Stephen Hewitt25-Apr-06 14:47

25-Apr-06 14:47

There are problems with this code: you have 2 variables called "p1" and 2 called "p2".
Anyway here how I'd read in a list of points:
----

// Console.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <fstream>
#include <iostream>
#include <vector>
#include <string>
using namespace std;

// Our point structure.
class My3DPoint
{
public:
My3DPoint() : x(0), y(0), z(0) {}
My3DPoint(int _x, int _y, int _z) : x(_x), y(_y), z(_z) {}
int x, y, z;
};

// A collection of "My3DPoint"s.
typedef vector<My3DPoint> My3DPoints;

int main(int argc, char* argv[])
{
ifstream in("C:\\a.txt");

My3DPoints points;

string label;
int x, y, z;
while (in >> label >> x >> y >> z)
{
points.push_back(My3DPoint(x, y, z)); // Add it to our collection.
}

// Now print the collection (in reverse order for fun):
typedef My3DPoints::reverse_iterator RI; // To save some typing.
for ( RI i=points.rbegin(); i!=points.rend(); ++i )
{
const My3DPoint &pt = *i;
cout << "(" << pt.x << ", " << pt.y << ", " << pt.z << ")\n";
}

return 0;
}

Steve

etm12425-Apr-06 14:55