how this code will work for bigger range number?

Question

if the range of d is 1<= d <= 10^101 and n is 1<= n <= 200. since the range of double is 2.3E-308 to 1.7E+308. when i take input 11111111111111111111 as d then the value d become 11111111111111111000.000 when i show the value to terminal. that means that it couldn't take the input correctly then how will it give correct value for 10^101. i need know the nth root of d. d will be always in form of p = k^n. that's why i added pow function to know the nth root. but the problem is that the range of p is huge. what i am trying is to solve this problem Power of Cryptography !

int main(){

 double d,n;

 scanf("%lf%lf", &n, &d))
 {
     printf("%lf\n", pow(d, 1/n));
 }

  return 0;
}

Welcome to the world of Floating Point numbers. You should take a look to the concept of precision. For arbitrary precision FP, see [MPFR](http://www.mpfr.org/). — Margaret Bloom, Feb 21 '16 at 10:03
@MargaretBloom - you understood the question? Maybe it's just me:( — Martin James, Feb 21 '16 at 10:04
@MargaretBloom lol! I cannot see how 'pow(d, 1/n)' could return a number larger than d if n is restricted to numbers 1-200, ie, >1 — Martin James, Feb 21 '16 at 10:08
@MartinJames no no, my question is that can d hold value up to 10^101 correctly ? — Razib Hossain Shuvo, Feb 21 '16 at 10:13
@RazibHossainShuvo No, it cannot hold 10¹⁰¹ correctly. But it can hold it sufficiently precisely to print out an approximate result. — fuz, Feb 21 '16 at 10:15
Possible duplicate of [Is floating point math broken?](http://stackoverflow.com/questions/588004/is-floating-point-math-broken) — Jongware, Feb 21 '16 at 10:22
Possible duplicate of [How many decimal places does the primitive float and double support?](http://stackoverflow.com/questions/28045787/how-many-decimal-places-does-the-primitive-float-and-double-support) — phuclv, Feb 21 '16 at 10:44

score 4 · Answer 1 · answered Feb 21 '16 at 10:16

A double precision number is not capable of holding all the values between 2.3E-308 to 1.7E+308, it is capable of holding a value between these numbers to a precision of about 15 decimal places.

That means some numbers (such as your example) require more precision than the 8 bytes of data can store.

how this code will work for bigger range number?

1 Answers1