DaniWeb Forum Index > Software Development > C++

C++ RSS

string to float problem

Please support our C++ advertiser: Intel Parallel Studio Home

•

Join Date: Jan 2008

Posts: 77

Reputation: number87 is an unknown quantity at this point

Solved Threads: 0

number87

Offline

Junior Poster in Training

string to float problem

Oct 26th, 2009

I am trying to convert a string "500.00" into float.

When I use this it produces a string 50000, why does it produce such a result?

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
atof(bal.c_str());
atof(bal.c_str());

•

Join Date: Jun 2009

Posts: 681

Reputation: Tom Gunn has much to be proud of

Solved Threads: 132

Tom Gunn

Offline

Practically a Master Poster

Oct 26th, 2009

It works OK for me. Maybe the problem is how you are printing the double that atof() returns. What does the following program print when you run it?

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <iomanip>
#include <string>
#include <cstdlib>
 
int main()
{
    std::string s("500.00");
 
    std::cout << std::fixed << std::setprecision(2)
              << std::atof(s.c_str()) << '\n';
}
#include <iostream>
#include <iomanip>
#include <string>
#include <cstdlib>

int main()
{
    std::string s("500.00");

    std::cout << std::fixed << std::setprecision(2)
              << std::atof(s.c_str()) << '\n';
}

-Tommy (For Great Justice!) Gunn

•

Join Date: Jan 2008

Posts: 77

Reputation: number87 is an unknown quantity at this point

Solved Threads: 0

number87

Offline

Junior Poster in Training

Oct 26th, 2009

ohh....I didnt include the setprecision and std::fixed. But if I include it, my code still doesnt print right. 500.00 as a string the float just becomes 50000.00

This is exactly what I did in my code.
It is in a function and I pass in string bal

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
float tt = atof(bal.c_str());
cout << tt;
float tt = atof(bal.c_str());
cout << tt;

Last edited by number87; Oct 26th, 2009 at 12:42 pm.

•

Join Date: Dec 2008

Posts: 1,180

Reputation: firstPerson is just really nice

Solved Threads: 147

firstPerson firstPerson is offline

Offline

Veteran Poster

Oct 26th, 2009

Use sstream;

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include<sstream>
#include<string>
using namespace std;
int main(){
   stringstream converter;
   string str= "3.14";
   converter << str ;  //put in string 
   float PI = 0;
   converter >> PI; //put out float
 return 0;
}
#include<sstream>
#include<string>
using namespace std;
int main(){
   stringstream converter;
   string str= "3.14";
   converter << str ;  //put in string 
   float PI = 0;
   converter >> PI; //put out float
 return 0;
}

Help with Code Tags

(Toggle Plain Text)

I give up! 
1) What word becomes shorter if you add a letter to it? [ Solved by : niek_e ]
2) What does this sequence  equal to :  (.5u - .5a)(.5u-.5b)(.5u-.5c) ...
3) What is the 123456789 prime numer?
Ask4Answer