Type conversions

[karanc]

Can anyone briefly explain to me how type conversion works in c ?

How do i convert a string(char array) to double type ?
Do I have to use the type conversion functions every time or will it convert implicitly in some cases ?

[parksie]

There's very few implicit conversions with strings. Basically it'll convert char* to string, and that's about it.

If you want to convert to double, it's easier than going the other way:

#include <cstdlib>

using namespace std;

int main() {
    const char *s = "-5.6e-3";

    double d = atof(s);

    return 0;
}

[karanc]

Does that mean i can use atof for both conversion to float and double types depending on the type of the variable on the left hand side ?

[jim mcnamara]

whoa.

There are library functions in C that convert strings to floating point.

atof() converts a char string to a double.
atoi() converts a char string to an integer.
_ecvt() takes a double and makes a string out of it - backwards from atof().

There are other special functions that convert substrings to double, float, integer. strtod(), strtof(), strtol().

All of this is in Visual Studio Help, with examples.

[jim mcnamara]

The standard way to convert any number to a string is with
sprintf()

int i;
double j;
char tmp[20];
memset(tmp,0x0,sizeof(tmp));
sprintf(tmp,"%f",j);  // double to string
sprintf(tmp,"%d",i); // integer to string