[SOLVED] 2 4 8 16

[asmith]

do we got a function to check that whether a  number is  " 2 base " or not ?

sorry i don't know what it can be in english :

2 base :  2  4    8  16  32 ....

3 base :  3  9  27  81 ...

 

 

or i should code it individuali ?

[Syco54645]

There is base_convert, but it cannot check a number's base, merely convert it.  Not sure if that is what you meant.

http://php.net/base_convert

[obsidian]

There is base_convert, but it cannot check a number's base, merely convert it.  Not sure if that is what you meant.

http://php.net/base_convert

 

If I'm not mistaken, the description of the issue seems to be covering roots, not truly bases. If it were base 2, it would be binary and only contain 0s and 1s. So, correct me if I'm wrong, but you are wanting to find out whether or not a number has a root of X, correct?

 

If this is the case, I'm not sure there is a built in function to do it, but a function like this may help:

<?php
/**
* Checks whether number $n is a power of $root
* @param int $n
* @param int $root
* @return array
*/
function is_of_root($n, $root)
{
        $pow = 0;
        $x = 0;
        while ($x < $n)
        {
                ++$pow;
                $x = pow($root, $pow);
        }

        if ($n == $x)
        {
                return array(TRUE, $pow);
        }
        else
        {
                return array(FALSE, -1);
        }
}

header("Content-type: text/plain");
print_r(is_of_root(27, 3));
print_r(is_of_root(100, 10));
print_r(is_of_root(134217728, );
?>

 

As you can see, the first key of the array returned is a boolean TRUE or FALSE as to whether the provided number has a root of the $root provided, and the second element of the array is the magnitude that creates your number in question.

 

Hope this helps.

[asmith]

more like it, see this :

 

if (x is "2 base" )

echo "valid"

else (echo invalid)

 

 

if i set  x= 30 , the output is invalid ,  if the x=64  , the outpu tis valid

 

8  valid

16 valid

20 invalid

24 invalid

32  valid

40 invalid

128 valid

150 invalid

256 vald

512 valid

 

[obsidian]

I just updated my previous post with a function that may help... see above.

[asmith]

yea  it works,

but wanted to know maybe theres's a function for it

thanks  !

 

[obsidian]

yea  it works,

but wanted to know maybe theres's a function for it

thanks  !

 

I just browsed the math section of the PHP manual, and I can't find anything that is a reverse lookup like that. That is why I wrote up the function above quickly.

[asmith]

I just browsed the math section of the PHP manual, and I can't find anything that is a reverse lookup like that. That is why I wrote up the function above quickly.

 

thanks a bunch , you really helped!