incorrect stof() declaration

Question

I'm reading in values from a text file and printing the to screen as strings. The idea is to read in each individual string and print them to screen along with the running average of strings read in printed next to it. i have this for my string to float declaration

int main()
{

string inputfile, intstring;
float counter;
counter = 0;
float average;
average = 0;
float stringconv = stof(intstring);

cout << "Enter the name of a file to open\n";
cin >> inputfile;

ifstream inFile;
inFile.open(inputfile.c_str());

and later on to calculate the average

while (!inFile.eof())
{
    getline(inFile, intstring, ' '); 
    cout << intstring <<","<<average<< endl;
    //increments counter to keep average output correct
    counter = counter +1;
    //goes to next line at each space encountered in text file
    average = (counter + stringconv) /2;
}

I've included this just in case my issue lies there. Can anyone tell me how to properly declare my conversion? and here is a full version which compiles

#include <math.h>
#include <iostream>
#include <string>
#include <fstream>
using namespace std;

int main()
{

string inputfile, intstring;
float counter;
counter = 0;
float average;
average = 0;
float dividor;
dividor = 1;

cout << "Enter the name of a file to open\n";
cin >> inputfile;

ifstream inFile;
inFile.open(inputfile.c_str());

if (!inFile)
{
    cout << "Error opening file " << inputfile << endl;
    char stopchar;
    cin >> stopchar;
    return -1;
}

while (!inFile.eof())
{
//goes to next line at each space encountered in text file
getline(inFile, intstring, ' '); 
cout << intstring <<","<<average<< endl;
float stringconv;
stringconv = stof(intstring);

average = (counter + stringconv)/dividor ;
dividor = dividor +1;

//increments counter to keep average output correct



}

inFile.close();
char stopchar;
cin >> stopchar;
}

`while (!inFile.eof())` Whoops! Which learning resource taught you this? — Lightness Races in Orbit, Dec 06 '15 at 14:37
My university lecturers, they're pretty useless tbh. Ask a question in labs and you're generally met with shrugs and glazed expressions. — J0rdy, Dec 06 '15 at 14:38
Please provide [MCVE](http://stackoverflow.com/help/mcve). Are you sure you put some value to `intstring` before calling `stof(intstring)` in your actual code? — MikeCAT, Dec 06 '15 at 14:47
You've presented some code snippets that can't possibly compile and a vague reference to "incorrect stof declaration". Does the compiler give you an error message? If so, what is that message? If not, what, specifically, is the problem? — Pete Becker, Dec 06 '15 at 14:47
See [`while (!feof(file))` is always wrong](http://stackoverflow.com/questions/5431941/while-feof-file-is-always-wrong) for a discussion of why people are aghast at `while (!inFile.eof())` — which is the C++ analogue of `while (!feof(inFile))`. — Jonathan Leffler, Dec 06 '15 at 15:39

Beta · Answer 1 · 2015-12-06T16:30:27.990

Here:

string inputfile, intstring;
...
float stringconv = stof(intstring);

You can't do that. I mean, you can, but it doesn't do what you think it does. You think you're creating a macro or function or something, so that you can change intstring and then stringconv will automatically change. But what you're actually doing is converting the uninitialized string into an integer once, and never changing it again. You must do the conversion inside the read loop.

EDIT: If you're not required to use stof(), then you can save yourself a lot of headaches by using the stream input operator:

float number;
inFile >> number;       // this is the basic form
while(inFile >> number) // this is how to do it as a loop
  ...

score 0 · Answer 2 · answered Dec 06 '15 at 14:49

In C++, float stringconv = stof(intstring); won't meen automatic conversion like assign in Verilog.

Call stof() each time you need to convert.

Try this:

while (!inFile.eof())
{
    getline(inFile, intstring, ' '); 
    cout << intstring <<","<<average<< endl;
    //increments counter to keep average output correct
    counter = counter +1;
    //goes to next line at each space encountered in text file
    stringconv = stof(intstring); // add this here
    average = (counter + stringconv) /2;
}

cheers man, its outputting now but still breaking at the argument of stof while running in debug mode — J0rdy, Dec 06 '15 at 15:02

incorrect stof() declaration

2 Answers2