How do I write only the decimal places in C language? - c

Question

If I have 2.55, how do I write only .55 and skip 2 in programming language?

Answer 1

Well you can do this to store it in another variable -
double a=2.55,b;
b =a-(long)a; // subtracting decimal part from a
printf("%.2f\n",b);
As pointed out by Mark Dickinson Sir in comment that this is not safe . So you can make use of function modf from <math.h>-
For example -
double a=-2.55,b,i;
b =modf(a,&i); // i will give integer part and b will give fraction part
printf("%.2f\n",b);

Answer 2

Use double modf(double value, double *iptr) to get the factional part. Use round() to get the best value near the requested precision.
double GetDecimalPlaces(double x, unsigned places) {
double ipart;
double fraction = modf(x, &ipart);
return fraction;
// or
double scale = pow(10.0, places);
return round(fraction * scale)/scale;
}
void GetDecimalPlaces_Test(double x, unsigned places) {
printf("x:%e places:%u -->", x, places);
printf("%#.*f\n", places, GetDecimalPlaces(x, places));
// Additional work needed if leading '0' is not desired.
}
int main(void) {
GetDecimalPlaces_Test(2.55, 2);
GetDecimalPlaces_Test(-2.55, 2);
GetDecimalPlaces_Test(2.05, 2);
GetDecimalPlaces_Test(0.0, 2);
GetDecimalPlaces_Test(0.0005, 2);
}
Output
x:2.550000e+00 places:2 -->0.55
x:-2.550000e+00 places:2 -->-0.55
x:2.050000e+00 places:2 -->0.05
x:0.000000e+00 places:2 -->0.00
x:5.000000e-04 places:2 -->0.00

Answer 3

One dirty trick is to cast your double to an int to get only the whole number. You can then subtract the two to get only the decimal part:
double d = 2.55;
double remainder = d - (int)d;
printf ("%.2f\n", remainder);

Answer 4

double values are not perfectly precise, so small rounding errors can get introduced. You can store the total number in an Integer. You can for example divide by 100 to get the value before the . and use % modulus to get the decimal values.
Example:
int main()
{
int num = 255;
printf("%d.%d\n", num / 100, num % 100); // prints 2.55
printf(".%d", num % 100); // prints .55
return 0;
}
This fails with negative numbers, but you can easily add cases to handle that.