Question

I am working on a project and I have an idea on how to start. Basically this is how the program runs:

$ ./rulerbuddy 2.25
2.25 is exactly 2 1/4

So, I kind of have the idea that I need first to rip off the whole number which in this case is ‘2’ then start manipulating the fraction to get the result. My question is how can I rip off that whole number from the decimal fraction? Any ideas, steps, guide is appreciated. Thank you.

Answer 1

1. Take out the whole number and consider only the decimal part (do a sscanf(input, "%d.%d", &intPart, &fracPart) to take them apart).

2. Count the digits after the decimal point; your starting fraction is digits/10^number of digits, i.e. in your case 25/100;

3. Now you can simplify it finding the greatest common divisor (e.g. with Euclid algorithm) and dividing both terms by it.

Quick example of how this can be implemented:

#include <stdio.h>
#include <math.h>

struct Fraction
{
    int n;
    unsigned int d;
};

int gcd(int a, int b)
{
    if(b==0)
        return a;
    else
        return gcd(b, a-b*(a/b));
}

void simplify(struct Fraction * f)
{
    int divisor=gcd(f->n, f->d);
    f->n/=divisor;
    f->d/=divisor;
}

int main(int argc, char * argv[])
{
    int intPart;
    unsigned int fracPart;
    struct Fraction f;
    if(argc<2)
    {
        puts("Not enough arguments.");
        return 1;
    }
    if(sscanf(argv[1], "%d.%u", &intPart, &fracPart)!=2)
    {
        puts("Invalid input.");
        return 2;
    }
    f.n=fracPart;
    f.d=fracPart!=0?(int)pow(10., floor(log10(fracPart)+1)):1;
    simplify(&f);
    printf("%s is exactly: %d %d/%u\n", argv[1], intPart, f.n, f.d);
    return 0;
}