How do you round doubles similar to how the printf function does it?

[chaoswings]

How do you round doubles similar to how the printf function does it?

if I have the following program....

main ()
{
double num;
num=12.45672

printf("%7.2lf");

}

printf will round it and put it up on the display....how do I round it in that exact fashion and then use it in an equation...

i tried do do it by using....


double round(double num){
double a1,result;
a1=(double)(num*100)/100;
result=a1;

return result;

}

but it doesn't round it the same way for all numbers

[Euphoracle]

double round(double num){

double result;
result=(double)(((int)(num*100))/100);

return result;

}

Casting it to an int will kill the decimals after it has been multiplied by 100, then dividing it will keep the old ones when casting back to double. If you want more decimal places, I recommend adding something along the lines of:

int places = 3;
int rounder = pow(10, places);

and then:

result = (double)(((int)(num*rounder)/rounder);

[md]

you need to cast remainder to a double when you do the division, otherwise you'll be dividing an int by an int which results in an int.