Converting a char array with decimal numbers to different float - c

Question

Hello I´m fairly new to C programming and i want to convert a char array looking like
char numberlist[]="9,8 2,3 5,4 2,7 1,3";
to a float that would be 9.8 ,i used
float a;
a=atof(numberlist);
printf("%.1f\n",a);
but that gave me 9.0 in return because it is 9,8 instead of 9.8 in the char array. How could i easily fix that, without touching the char array?
Thanks in advance :)

Answer 1

For example
char numberlist[]="9,8 2,3 5,4 2,7 1,3";
float convertFirstNumber(const char *str, char delim)
{
char z[256];
size_t index = 0;
while(*str && *str != delim)
{
if(*str == ',') z[index++] = '.';
else z[index++] = *str;
str++;
}
z[index] = 0;
return atof(z);
}
int main()
{
printf("%.1f\n",convertFirstNuber(numberlist, ' '));
}

Answer 2

This can be done with int sscanf(const char *restrict s, const char *restrict format, ...); and atof i have chossed sscanf to show u different approach. you can replace it with atof if you wish.
int main(){
float f, resd;
int i = 0;
char numberlist[]="9,8 2,3 5,4 2,7 1,3";
sscanf(numberlist,"%f",&f);
while(numberlist[i] != ','){
++i;
}
sscanf(&numberlist[i],",%f",&resd);
printf("%f\n", resd);
printf("%f",f+resd/10.0);
return 0;
}

Answer 3

If your string uses a comma as decimal point, you could set the locale to a useful value before parsing:
/* Set number locale to german */
setlocale(LC_NUMERIC, "de_DE.utf8");
double a; /* Never use floats */
sscanf("3,14", "%lf", &a);
/* It is better to not hardcode "C" but use the locale saved before the
previous `setlocale` */
setlocale(LC_NUMERIC, "C");
/* Should print "3.14" */
printf("%lf\n", a);
Just remember that setlocale has issues with multithreaded software. And you should reconsider if you really want to store your data with comma as the decimal point.

Answer 4

Adam gave a good answer.
You can also iterate the string and create the number manually.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
char numberlist[] = "9,8 2,3 5,4 2,7 1,3";
int main() {
int len = strlen(numberlist);
int total = 0;
int count = 0;
for(int i = len; i >= 0; i--){
char c = numberlist[i];
if(isdigit(c)){
int number = atoi(&c);
total += round(pow(10, count)) * number;
count++;
}
}
float value = total / round(pow(10, count-1));
printf("%.2f\n", value);
}