-1.#IND000 problem

[iCe CreaM]

I am working on code to calculate the factorial using below function:

int factorial (int num)
{
if (num==1)
return 1;
return factorial(num-1)*num; // recursive call
}


And I need to calculate the numbers from 1 to 255…

The problem occurs when it reaches number 35 and above, it starts to give -1.#IND000 as result for the calculation…

I tried to define the variable as float, double , long double but it doesn’t work!

[Laharl]

Those numbers are far too large for even long doubles. You'll need to find (or write) a library capable of working with such huge numbers.

[Motoma]

Hi iCe CreaM,

You will want to take a look at an Arbitrary-precision arithmetic library, or else create your own to help with this task.
If you take a look at the article I hyperlinked, there is a section mentioning factorials!

Good luck,
Motoma

I am working on code to calculate the factorial using below function:

int factorial (int num)
{
if (num==1)
return 1;
return factorial(num-1)*num; // recursive call
}


And I need to calculate the numbers from 1 to 255…

The problem occurs when it reaches number 35 and above, it starts to give -1.#IND000 as result for the calculation…

I tried to define the variable as float, double , long double but it doesn’t work!

[iCe CreaM]

first of all thanks guys for your replies...

i gounf the library http://gmplib.org/#WHAT

they said that it is the best in this regard but i couldn't know how to install it or use it in my C++ program :(

i tried to read the manual but no result...

thanks.

[sicarie]

So what is your question, and what have you tried?

[RedSon]

So what is your question, and what have you tried?

Just for fun 170! is:

725741562 followed by 298 zeros, give or take. Or in notation its 7.25741562 × 10^306

[JosAH]

Just because people can't comprehend the size of factorials, maybe Stirling's
approximation can be of any insight:

ln(n!) ~= n*ln(n)-n

Just plug in some values for n and play with your calculator ;-)

kind regards,

Jos