Comments on: PHP Math Library http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/ 1111111 * 1111111 = 1234567654321 Fri, 25 Jul 2008 05:41:15 +0000 http://wordpress.org/?v=2.5.1 By: Alix http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-257 Alix Sun, 12 Aug 2007 05:24:05 +0000 http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-257 Ok, I got so unhappy with the number_format behavior that I've made my own Number_Format() method for the Math class, I hope you like it. Ok, I got so unhappy with the number_format behavior that I’ve made my own Number_Format() method for the Math class, I hope you like it.

]]> By: Alix http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-256 Alix Sun, 12 Aug 2007 04:00:03 +0000 http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-256 Thanks P L Patodia, I've double checked my code and the expected results are correct, the problem here resides in the number_format() PHP function that I've used for the presentational purpose of this blog (it wouldn't word wrap it otherwise) - it seems like when you tell number_format() to format a really large number the outcome result is wrong. I'll code my own Number_Format() method to handle big numbers and I'll post it here as soon as I finish it. I've already reported the bug to the PHP team and had to manually add thousands separators to the real 1000th Fibonacci number, thank you very much for your feedback! Thanks P L Patodia, I’ve double checked my code and the expected results are correct, the problem here resides in the number_format() PHP function that I’ve used for the presentational purpose of this blog (it wouldn’t word wrap it otherwise) - it seems like when you tell number_format() to format a really large number the outcome result is wrong. I’ll code my own Number_Format() method to handle big numbers and I’ll post it here as soon as I finish it.

I’ve already reported the bug to the PHP team and had to manually add thousands separators to the real 1000th Fibonacci number, thank you very much for your feedback!

]]> By: P L Patodia http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-255 P L Patodia Sun, 12 Aug 2007 03:13:41 +0000 http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-255 The value of 1000th Fibonacci number provided by you is not correct. The correct value is 4346655768693745643568852767504062580256466051737178040248172 9089536555417949051890403879840079255169295922593080322634775 2096896232398733224711616429964409065331879382989696499285160 03704476137795166849228875 This is computed using gp-pari. The value of 1000th Fibonacci number provided by you is not correct. The correct value is

4346655768693745643568852767504062580256466051737178040248172
9089536555417949051890403879840079255169295922593080322634775
2096896232398733224711616429964409065331879382989696499285160
03704476137795166849228875

This is computed using gp-pari.

]]> By: Alix http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-254 Alix Wed, 08 Aug 2007 01:53:24 +0000 http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-254 Regarding the Math::$bcmath_enabled and Math::$gmp_enabled I'm aware of it, it would still produce the same error if I had used == or any other comparison operator. The reason for these variables being private is that this Math library is part of a much greater library framework I'm developing which runs on a base Singleton pattern class and therefore it doesn't produce those fatal errors. I've forgot to change this when I released it to the public - I'll do it now though. Regarding the Math::$bcmath_enabled and Math::$gmp_enabled I’m aware of it, it would still produce the same error if I had used == or any other comparison operator. The reason for these variables being private is that this Math library is part of a much greater library framework I’m developing which runs on a base Singleton pattern class and therefore it doesn’t produce those fatal errors. I’ve forgot to change this when I released it to the public - I’ll do it now though.

]]> By: ed http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-253 ed Wed, 08 Aug 2007 01:40:54 +0000 http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-253 Wow, that was quick! I had forgotten the purpose of the static keyword. Any reason that factors[] should be a class variable instead of an instance variable? Another nit. Math()->$bcmath_enabled and $gmp_enabled should either be <b>public</b> or accessible via public get and set methods (I think). Here's what happens if they are left <b>private</b>. PHP Fatal error: Cannot access private property Math::$gmp_enabled in C:\Development\www\math \Number_Theory.php on line 228 Apparently, PHP doesn't let you check the type (the "===" operator) of private data. Wow, that was quick! I had forgotten the purpose of the static keyword. Any reason that factors[] should be a class variable instead of an instance variable?

Another nit. Math()->$bcmath_enabled and $gmp_enabled should either be public or accessible via public get and set methods (I think). Here’s what happens if they are left private.

PHP Fatal error: Cannot access private property Math::$gmp_enabled in C:\Development\www\math
\Number_Theory.php on line 228

Apparently, PHP doesn’t let you check the type (the “===” operator) of private data.

]]> By: Alix http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-252 Alix Wed, 08 Aug 2007 00:51:35 +0000 http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-252 The Factor() bug it's solved! :) Now it returns the correct result: <strong>print_r($Number_Theory->Factor(20));</strong> Array ( [2] => 2 [5] => 1 ) 20 = 2^2 * 5^1 (correct) <strong>print_r($Number_Theory->Factor(10));</strong> Array ( [2] => 1 [5] => 1 ) 10 = 2^1 * 5^1 (correct) I had to add an extra variable to reset the factors, I couldn't find any other way to solve the bug... The source code has been updated, you can find the changes there. ;) The Factor() bug it’s solved! :) Now it returns the correct result:

print_r($Number_Theory->Factor(20));

Array
(
[2] => 2
[5] => 1
)

20 = 2^2 * 5^1 (correct)

print_r($Number_Theory->Factor(10));

Array
(
[2] => 1
[5] => 1
)

10 = 2^1 * 5^1 (correct)

I had to add an extra variable to reset the factors, I couldn’t find any other way to solve the bug… The source code has been updated, you can find the changes there. ;)

]]> By: Alix http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-251 Alix Wed, 08 Aug 2007 00:17:34 +0000 http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-251 Hi Ed, thanks for warning me about this unexpected behavior. The bug you presented seems to be caused by a misuse of the static variable $factors (line 81), which is needed to store the factorization made if the script needs to re-factorize a certain number (line 116). The problem is that the static variable $factors maintains its state until the script is finished and that causes it to also add the factors of previous factorizations. :( The good news is that this is the only method where I've used static variables, so as soon as I solve it I'll post here the solution and I'll update the source code. Again, many thanks for your info! ;) Hi Ed, thanks for warning me about this unexpected behavior.

The bug you presented seems to be caused by a misuse of the static variable $factors (line 81), which is needed to store the factorization made if the script needs to re-factorize a certain number (line 116).

The problem is that the static variable $factors maintains its state until the script is finished and that causes it to also add the factors of previous factorizations. :(

The good news is that this is the only method where I’ve used static variables, so as soon as I solve it I’ll post here the solution and I’ll update the source code.

Again, many thanks for your info! ;)

]]> By: ed http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-250 ed Tue, 07 Aug 2007 23:39:05 +0000 http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-250 oops, darn wordpress. my code snippet was truncated. require('Number_Theory.php'); $foo = new Number_Theory(); print_r($foo->Factor(20)); $bar = new Number_Theory(); print_r($bar->Factor(10)); oops, darn wordpress. my code snippet was truncated.

require(’Number_Theory.php’);

$foo = new Number_Theory();
print_r($foo->Factor(20));

$bar = new Number_Theory();
print_r($bar->Factor(10));

]]> By: ed http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-249 ed Tue, 07 Aug 2007 23:35:46 +0000 http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-249 Forgive my relative ignorance of OO, but why doesn't this test.php work? Factor(20)); $bar = new Number_Theory(); print_r($bar->Factor(10)); ?> I get this unexpected result... Array ( [2] => 2 [5] => 1 ) Array ( [2] => 3 [5] => 2 ) Why does the factors array persist? Forgive my relative ignorance of OO, but why doesn’t this test.php work?

Factor(20));

$bar = new Number_Theory();
print_r($bar->Factor(10));
?>

I get this unexpected result…

Array
(
[2] => 2
[5] => 1
)
Array
(
[2] => 3
[5] => 2
)

Why does the factors array persist?

]]> By: Alix http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-30 Alix Wed, 13 Jun 2007 16:52:06 +0000 http://www.alixaxel.com/wordpress/2007/05/19/php-math-library/#comment-30 Now also on http://www.numbertheory.org/ntw/N1.html thanks to Keith Matthews! :) Now also on http://www.numbertheory.org/ntw/N1.html thanks to Keith Matthews! :)

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