read from txt file C++

[HalfVector]

Hi.

Try using the iostream library. Here (http://home.wanadoo.nl/efx/c++-faq/misc-technical-issues.html#faq-39.2) you have an example.

[AzHisoka]

So you just want to convert a string to an int? Can't you just do atoi?

[fbitonti]

I am able to import however, now i'm stuck with a string that i have to convert.

this is a sample of what I am doing. I would like to stick with this method for converting the string I know it can be done other ways but i would like to make this one work for other reasons that come into play later in the program. however, i may be open to other methods if this absolutly will not work.

for some reason when I convert the string into an int or flaot i gives me back a zero can some one tell me what is going on.

the text file that I am reading from has two numbers on two different likes. one is 20000 the other is 40.5

// Declare the necessary variables.
std::string line;
// Define a file object.
std::ifstream fileInput("C:/2dTrussMaterials.txt");

//std::string s = 28383;
//double x = convertToDouble(s);

std::string material[3];

int matQuery = 0;
// // Read in all data.
while (std::getline(fileInput, line, '|')) { // Reads in a quote.
//
// // Print the quote.
// std::cout << line << "\n - ";
//
// // Get and print the speaker.
std::getline(fileInput, material[matQuery]);
// std::cout << line << "\n\n";
//
matQuery = matQuery+1;
//
} // End of WHILE.
//
// // Close the stream.
fileInput.close();
//

int e = atoi(material[0].c_str());
float a = atoi(material[1].c_str());

[janimatic]

you should use stringstream instead, it provide the same conversion capability as iostreams.
Something like that :

#include <iostream>
int yourIntValue;
std:string yourStringFromGetline;

//while getline etc....
std::istringstream parser;
parser.str(yourStringFromGetline);
parser >> yourIntValue;
//end while

[fbitonti]

ok this is what i've got now. it spits back different values than what I put into it.

they should be
e= 200000
and a = 4000

instead i get
e= -858993460
a = -858993472

this is the code i'm working with right now.

// Declare the necessary variables.
std::string line;
// Define a file object.
std::ifstream fileInput("C:/2dTrussMaterials.txt");

//std::string s = 28383;
//double x = convertToDouble(s);
int txtmaterial[3];
std::string material[3];

int matQuery = 0;
// // Read in all data.
while (std::getline(fileInput, line, '|')) { // Reads in a quote.
//
// // Print the quote.
// std::cout << line << "\n - ";
std::istringstream parser;
// // Get and print the speaker.
std::getline(fileInput, material[matQuery]);
// std::cout << line << "\n\n";

parser.str(material[matQuery]);
parser >> txtmaterial[matQuery];

matQuery = matQuery+1;
//
} // End of WHILE.
//
// // Close the stream.
fileInput.close();
//
int e = txtmaterial[0];
float a = txtmaterial[1];

I feel like it's getting close to working you will have to excuse me if i am missing a basic step i'm just starting to learn c++ and am teaching myself. I appreciate all the help i can get thanks again

[janimatic]

could you start by using sinmple int and string before using arrays and pointers, that would probably make it easier to track the problem

[fbitonti]

i have also been trying to do it this way.

convert.h
// File: convert.h
#include <iostream>
#include <sstream>
#include <string>
#include <stdexcept>

class BadConversion : public std::runtime_error {
public:
BadConversion(const std::string& s)
: std::runtime_error(s)
{ }
};

inline int convertToInt(const std::string& s)
{
std::istringstream i(s);
int x;
if (!(i >> x))
throw BadConversion("convertToInt(\"" + s + "\")");
return x;
}

inline int convertToFloat(const std::string& s)
{
std::istringstream i(s);
float x;
if (!(i >> x))
throw BadConversion("convertToFloat(\"" + s + "\")");
return x;
}

then i use those functions in the main cpp file

#include <stdio.h>
#include <cstdlib>
#include <math.h>
#include <fstream>
#include <string>
#include <iostream>
#include "convert.h"

// Declare the necessary variables.
std::string line;
// Define a file object.
std::ifstream fileInput("C:/2dTrussMaterials.txt");

//std::string s = 28383;
//double x = convertToDouble(s);
int txtmaterial[3];
std::string material[3];

int matQuery = 0;
// // Read in all data.
while (std::getline(fileInput, line, '|')) { // Reads in a quote.
//
// // Print the quote.
// std::cout << line << "\n - ";
std::istringstream parser;
// // Get and print the speaker.
std::getline(fileInput, material[matQuery]);
// std::cout << line << "\n\n";

parser.str(material[matQuery]);
parser >> txtmaterial[matQuery];

matQuery = matQuery+1;
//
} // End of WHILE.
//
// // Close the stream.
fileInput.close();

// //E modulus of elasticity

int e = convertToInt(material[0]);
//
// //A area of section

float a = convertToFloat(material[1]);

I've been at this for days and i'm getting soo confused some one please help me! lol thanks again.

[fbitonti]

the method in the last post compiles fine with no errors however there seems to be a memory problem because when i run the plugin in maya it dosn't give me any output. at all some error is breaking the commands i know the error is from this portion of code because without this code the plugin works fine.

[janimatic]

int txtmaterial[3];
std::string material[3];


while (std::getline(fileInput, line, '|')) { // Reads in a quote.

} // End of WHILE.


those are the part of the code i would look for error.

- Could you test without using arrays ???
once it will work fine , and when you need arrays in general you can use a std containers instead : vector .
But i don't see why you need an array of strings ????
Just reuse the same
std::string material;
object for each
std::getline(fileInput, material);

- aint this loop blocking ?

- oh and you are using getline twice !
you should use "line" string variable (make sure it has the expected content by printing it) , convert it to stringstream and get the values from this.

[fbitonti]

GOT IT! thank soo much every one.

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.