How to convert a string/ char array to a double or float? None of the standard libs seem to want to work

Mbed OS Best practice
,
1

#include “mbed.h”
#include
#include
#include
#include

using namespace std;

int ascii_to_int_conv(char ascii);
double ascii_to_double_conv(char ascii);

int main(){

printf("\033[2J\033[1;1H");  // clear terminal 


//string that needs to be converted
string str = "54.1"; // input


char charArray[str.length() + 1]; // +1 for null terminator

//fill char array 
strcpy(charArray, str.c_str()); // fills the char with the sting 

// output the copy 
cout << "Result: " << charArray << endl;    // output to check the char converstion has been done



double result;   
// standard lib convertion  
result = atof(str.c_str());
//   OUTPUT: result 536895960

result = ascii_to_double_conv(charArray); // convert the array to double
result = ascii_to_int_conv(charArray); // convert the array to double

printf("result %d\n" , result);
// cout << "Result: " << result << endl;   //output the result

}

int ascii_to_int_conv(char ascii)
{

//cout << ascii << endl;
int idx = (sizeof(ascii)) - 2;
int value = 0;

// Fill each element of the value array individually
for (int i = 0; i < idx; ++i) {
    value = value * 10 + (ascii[i] - 48);
}

// Output the entire concatenated number
//cout << "The concatenated number is: " << value << endl;
printf("the concatenated number is %i \n", value );


return value;

}

double ascii_to_double_conv(char ascii) {
int idx = sizeof(ascii);

double value = 0.0;
double decimalMultiplier = 1.0; // To handle decimal places

int decimalPointIndex = -1;

// Fill each element of the value array individually
for (int i = 0; i < idx; ++i) {
    if(ascii[i] == '.')
    {
        decimalPointIndex = i;
    }

    if (decimalPointIndex != -1)
    {
        value = value * 10 + (ascii[i] -48);
        decimalMultiplier *= 0.1;
    }
    else 
    {
        value = value * 10 + (ascii[i] - 48);
    }

}

   // Adjust value for decimal places
if (decimalPointIndex != -1) {
    value *= decimalMultiplier;
}


printf("The concatenated number is: %d\n", value);

return value;

}

2

Hello,

first check this

https://cplusplus.com/reference/cstdio/printf

BR, Jan

4

Thank you for the help! to resolve the issue on the Nucleo-F429ZI the following code needs to be added to a JSON file under the main folder called mbed_app.json

{
“target_overrides”: {
“NUCLEO_F429ZI”: {
“target.printf_lib”: “std”
}
}
}

this adds floating point printing functionality to the print lib as this is removed by default