how to convert inputted text to float on c++

Hi Experts;

i have c++ string to float conversation problem;
my scenario;
application getting variable from environment variable (APP) and convert to float and summing this float variable with loop variable and last step set environment variable with result

i compile this codes (foo.cpp)
c++ foo.cpp -o foo

but result

foo.cpp: In function âint main()â:
foo.cpp:18: error: cannot convert âfloatâ to âconst char*â for argument â2â to âint setenv(const char*, const char*, int)â
foo.cpp:21: error: cannot convert âchar*â to âfloatâ in assignment

how to convert inputted text to float on c++
my code ;

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <iostream>
#include <string>

using namespace std;

int main ()
{
  float temp_var;
  string env;
  int i;
   getline(cin,env);
   for (i=0;i<=100;i++)
   {
       temp_var = atof(getenv("APP"));  
       setenv("APP",temp_var+i,1);  
       cout << i << endl;
   }
   temp_var= getenv("APP");  
   cout << temp_var<< endl;
  return 0;
}
 

Thanks ..
nedimkAsked:
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jkrCommented:
For 'setenv()', the 2nd parameter needs to be a 'const char*', you cannot pass a float - you'll need to convert that first. Make that

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

using namespace std;

int main ()
{
  float temp_var;
  string env;
  int i;
   getline(cin,env);
   for (i=0;i<=100;i++)
   {
       stringstream ss;
       string val;
       temp_var = atof(getenv("APP"));  
       ss << (temp_var + i);
       val = ss.str();
       setenv("APP",val.c_str(),1);  // pass a 'const char*'
       cout << i << endl;
   }
   temp_var= getenv("APP");  
   cout << temp_var<< endl;
  return 0;
}
 
0

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