[SOLVED] Calculating high numbers

[Lumio]

Hi!

I try to calculate a high number: 2^100

so I make it like that:

pow(2, 100);

My result is 1.26765060023E+30

How can I calculate with that value. Or do I have to replace that by my own.

[Wildbug]

BCMath functions?

[Lumio]

Hey thanks! I'll try that... later But thanks!

[Lumio]

Okay... That's great... but I can't calc roots. For example:

bcpow(4, 0.5) -> should get 2 ... but I get 1

[Wildbug]

It looks like you can't use decimal numbers for the exponent.  There is a bcsqrt() function, though.

[utexas_pjm]

It makes more sense to use fractions anyway -- as x^(1/k) is the kth root of x.  Just create a function like:

 

<?php
function root($x, $k)
{
    return( ($x < 0 && $k % 2 > 0 ) ? -1 : 1 ) * pow(abs($x), 1/$k);
}
?>

 

Best,

 

Patrick

[Wildbug]

Eh, (a) I don't think that's arbitrary precision, and (b) 1/x is still evaluated as a non-integer.

 

Maybe there's an identity you can find to circumvent that limitation or a homemade function that will do what you want.

[utexas_pjm]

Oops, sorry I missed the arbitrary precision requirement.  Just FYI -- You can use non integer exponents in the pow() function.