PHP advanced math fuctions

Canacas

Well.. I have a bit of a problem. I'm preaty sure this is possibel but i dont know how. Therfore i need some help from a true php expert 🙂

My problem is as followed... first i type this regular code snippet.

$samba = $var8 ^ 3;

This works fine..... but when i do this (using decimals)

$samba = $var8 ^ 3.115;

The php is simply removing all the digits after the "." In that function it does look like it cant handel decimal numbers. But somehow it must be possibel to do a mathematical function like that with decimal numbers in php.

I hope somone here knows how and can help me.. I realy need to include those decimal numbers.

Thanks

Drakla

$samba = pow($var8, 2.51);

Canacas

I'm Sorry for this newbie question. But how does the POW function work? It deffinatly do not do the same as ^

Drakla

Were you trying to raise to a power, or do a bitwise xor? I assumed the former.

Mordecai

The caret (⁾ can be a little confusing. While this would be "to the power of" in math, it's Xor on a computer. "$a xor $b" means, quoting the manual, "bits that are set in $a or $b but not both are set." So this means any bit that is set in only one but not the other. Not quite "to the power of," but you could use other bitwise operators (<< and >>--or bitshift left and bitshift right, respectively) to do some ^2, which computers obviously do extremely fast.

That being said, you'll want to have a look at [man]pow/man which was previously mentioned. This works exactly like ^ in math, but does not take decimals in the powers. Therein lies your error. So, we'll move on to the next function.

[man]exp/man "calculates the exponent of e (the Neperian or Natural logarithm base)." How does this help you? Well, initially, it won't. However, with the combination of [man]log/man, it comes quite handy. We can use these two in combination, like so:

$samba = exp(3.115 * log($var8));

By the way, it's a good idea to look up all the functions and read their user notes. I learned this from one of the user notes, so here's a an in-depth explanation.

Drakla

Pow does work with decimals, give it a whirl. The manual needs updating as it's misleading.

Mordecai

Originally posted by Drakla
Pow does work with decimals, give it a whirl. The manual needs updating as it's misleading.

Whoaaah, I never remember it doing that. So I went into all that detail for nothing. 🙂

Oh well, might come in handy if he's using PHP 3. 😉

Canacas

hmm.. Now this is starting to get a little bit confusing. Let me clear a few things up. I give you the whole code.

// Mission: if you activate this variabel

// $userinfo_level = "99";

// The outcome of $var3 will be 1 000 000. (one million).
// What i want is the outcome to be 2 000 000 (two millions)
// I know this is obtain abel if i change the raising number (now 3) to 3.150515.
// But as the $var9^3; snippet dont allow decimal numbers i'm s**.
// So if somone can change that 3 number to 3.150515 so the outcome will be 2 000 000 i would be VERY glad

$var9 = $userinfo_level+1;
$var1 = $var9^3;
$var8 = $var9-1^3;
$var2 = $userinfo_level*$var1-$var8;
$var3 = $var2*$userinfo_level+1;

I hope i can get some feedback on this one!
:queasy:

Mordecai

Replace all the ^s to use [man]pow/man:

$var9 = $userinfo_level+1;
$var1 = pow($var9, 3.150515);
$var8 = pow($var9-1, 3.150515);
$var2 = $userinfo_level*$var1-$var8;
$var3 = $var2*$userinfo_level+1;

laserlight

// Mission: if you activate this variabel

// $userinfo_level = "99";

// The outcome of $var3 will be 1 000 000. (one million).

The outcome is 9800990200
If we take
$var8 = $var9-1^3;
as
$var8 = ($var9-1)^3; //^ => exponential
Then the outcome is 9704940400

You might want to re-look your calculations.
Do you even need those intermediate variables anyway?
There's a lot of simplification that can be performed if you dont.

Canacas

Hmmmm... I have checked my calculations over and over agen. And i still get one million.. May this be caused by different versions of PHP/configs?

laserlight

I have checked my calculations over and over agen. And i still get one million.. May this be caused by different versions of PHP/configs?

Cant be - arithmetic is arithmetic.

Why dont you express your calculations using mathematical expressions instead of incorrect PHP code?

Weedpacket

Originally posted by Canacas
My problem is as followed... first i type this regular code snippet.

$samba = $var8 ^ 3;

This works fine.....

It does? It does something but if you're after exponentiation then it's not going to work any better than what you say doesn't work. (All it does is xors the last two bits of $userlevel_info, so $samba (whatever that is) is always either 0, 1, 2, or 3).

What exactly are you trying to achieve with all your calculations? It's hard to say from just looking at your code (there's a point where you add one, and then you just subtract one again). It looks as though you've just been thrashing about until you got something that looked right with one $user_info. And if you've been doing that then the code you've written could end up doing anything with different input.

Canacas

Originally posted by Weedpacket
What exactly are you trying to achieve with all your calculations? It's hard to say from just looking at your code (there's a point where you add one, and then you just subtract one again). It looks as though you've just been thrashing about until you got something that looked right with one $user_info. And if you've been doing that then the code you've written could end up doing anything with different input. [/B]

Look here http://www.engasjert.net/skisse/sheldurEXP2.htm

The tabel to the left is looping itself with the code i have posted here before. You will see that for level 100 you get 1 000 000.

To the right it is a non looping tabel giving out what number you must use to get to 2 000 000 in level 100. Then one more to the right of that one agen telling you the number for 5 000 000.

(PS the numbers are not generated in that file. Its just a print from a long gone excel file)

I hope you understand =) My english is not the best and i'm not a good explenatior. (or whatever you guys/girls call it 😛 )

This is somewhat a level formula for a game i'm creating. So the code will see how much experience you need for the next level. So if $userinfo_lvl is 99 you will need 1 000 000 million xp for level 100. (explenation. when level 99 you should already have 970299xp so its not that long way to one-millionxp)

laserlight

The tabel to the left is looping itself with the code i have posted here before. You will see that for level 100 you get 1 000 000.

The expression that generates that is 1003, where denotes exponentiation.

From what I see, you're looking to solve for x:
100**x = 1000000c
Taking logarithms on both sides, using the common (i.e. base 10) logarithm:
x = log(c) / 2 + 3

This explains why to map 100 to 2000000 you need to use 3.150515
Here c = 2000000/1000000=2, hence x = log(2)/2+3, using the common logaritm.

The PHP code itself is then trivial.
Given a certain value of c as $c, just compute:

$x = log10($c) / 2 + 3;
$samba = pow($userinfo_level, $x);

or even

$samba = pow($userinfo_level, log10($c) / 2 + 3);

Canacas

Thanks to all the replys and specialy to laserlight for giving me the "right" answer. 🙂

If anyone want to see the script in action you could simply go to http://www.sheldur.com and sign up at the re-launche tomorrow. (possibly)

Thanks agen 😃