Transformation from char to float

Hi,
I try to read a number from a char variable. The value of the char is something like "$GPGGA,11111.11,...". I would like to transform the "11111.11" to his float value (11111.11). I am using the BCB6. Is there any command in C++ to do it?

Thanks,
Ronald    
LVL 1
rsch1973Asked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

GloomyFriarCommented:
There is the function in Delphi.
function StrToFloat(const S: string): Extended;

I think that there is the same function in BCB
0
grg99Commented:
One simple way woul dbe to use strchr() to find the first comma, then strchr() from there+1 to find the nexxt one,
then strncpy to extract the number to another string variable, then sscanf or atof() on that.

0
GloomyFriarCommented:
Sample from MSDN:

/* SSCANF.C: This program uses sscanf to read data items
 * from a string named tokenstring, then displays them.
 */

#include <stdio.h>

void main( void )
{
   char  tokenstring[] = "15 12 14...";
   char  s[81];
   char  c;
   int   i;
   float fp;

   /* Input various data from tokenstring: */
   sscanf( tokenstring, "%s", s );
   sscanf( tokenstring, "%c", &c );
   sscanf( tokenstring, "%d", &i );
   sscanf( tokenstring, "%f", &fp );

   /* Output the data read */
   printf( "String    = %s\n", s );
   printf( "Character = %c\n", c );
   printf( "Integer:  = %d\n", i );
   printf( "Real:     = %f\n", fp );
}

Output
String    = 15
Character = 1
Integer:  = 15
Real:     = 15.000000

0
Introduction to Web Design

Develop a strong foundation and understanding of web design by learning HTML, CSS, and additional tools to help you develop your own website.

bcladdCommented:
In addition to sscanf, atof will convert a pointer to a C-style string (char * at a null-terminated string). You can use grg99's suggestion to find the beginning of the string you want to convert and then call atof:

char * theLine;
// you read the value into theLine here
const char * comma;
comma = strchr(theLine, ',');
++comma;
float value = atof(comma);


Hope this helps, -bcl
0
jkrCommented:
Try

#include <string>
#include <sstream>
#include <iostream>
#include <stdlib.h>

using namespace std;

void main () {

    float f;
    char* pc;
    string s;
    stringstream ss;

    ss << "$GPGGA,11111.11,...";

    getline ( ss, s, ','); // extract 'til 1st ','

    cout << s << endl;

    getline ( ss, s, ','); // extract 'til 2nd ','

    cout << s << endl;

    f = (float) strtod ( s.c_str (), &pc); // convert to 'float'

    cout << f << endl;
}
0
antoinebfCommented:
Hi,
What follows is a nice way of doing it with STL:

#include <sstream>
#include <string>
...
    float fValue(0);
    std::string myString("$GPGGA,11111.11,...");
    std::string::size_type pos1 = myString.find_first_of(',', 0);
    if (pos1 != std::string::npos)
    {
        std::string::size_type pos2 = myString.find_first_of(',', pos1 + 1);
        std::string subString(myString.substr(pos1 + 1, pos2 != std::string::npos ? pos2 - pos1 - 1 : std::string::npos));
        std::istringstream iss(subString);
        iss >> fValue;
    }
...

You can obviously play with the condition to make sure you convert only if possible, or if other conditions are met, but the basic idea here is the use the right shift operator.

hth

A.
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
fsign21Commented:
Or try this:

#include <string>
#include <iostream>
#include <sstream>
#include <stdlib.h>

using namespace std;

void main () {
  double d;
  string val("$GGG-1111.11TZR$");
  size_t pos = val.find_first_of("+-0123456789");

  if(pos==string::npos) {//not found
    d = 0.0;
  } else {
//1.Solution => use atof
  d= atof(val.c_str()+pos);

//2.Solution => use stringstream
  stringstream sio;
  sio << val.substr(pos);
  sio >> d;
  }
  cout << "Double: " << d << endl;
}
 
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
C++

From novice to tech pro — start learning today.