Re: [PHP-DEV] Re: #41401 [Opn-Bgs]: Order of Operations error on divide by negative
On Wed, May 16, 2007 9:08 am, Brian Moon wrote: According to my memory of Please My Dear Aunt Sally these should be: My memory has My Dear in equal priority, left to right... This documentation would seem to bear that out: http://us.php.net/manual/en/language.operators.php#language.operators.precedence -1/2*5 = -.1 1/-2*5 = -.1 1/2*-5 = -.1 Those are most definately all wrong. :-) So, that is bad if PHP answers that way. Someone please correct me if my memory is wrong. Is there some rule that negative values should be done first before positive values? Yes. The unary - operator buried in the third line that table is that rule. -- Some people have a gift link here. Know what I want? I want you to buy a CD from some indie artist. http://cdbaby.com/browse/from/lynch Yeah, I get a buck. So? -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
[PHP-DEV] Re: #41401 [Opn-Bgs]: Order of Operations error on divide by negative
[EMAIL PROTECTED] wrote: ID: 41401 Updated by: [EMAIL PROTECTED] Reported By: drlippman at yahoo dot com -Status: Open +Status: Bogus Bug Type: Math related Operating System: Windows, Linux PHP Version: 4.4.7 New Comment: [2007-05-15 15:44:07] drlippman at yahoo dot com Description: Left-to-right order of operations does not appear to be honored when dividing by a negative Reproduce code: --- 1/-2*5 Expected result: -2.5 Actual result: -- -.1 Should all these three examples give the same result? $ php -r 'var_dump(-1/2*5, 1/-2*5, 1/2*-5);' float(-2.5) float(-0.1) float(-2.5) Regards, -- Michael -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DEV] Re: #41401 [Opn-Bgs]: Order of Operations error on divide by negative
On 16/05/07, Uwe Schindler [EMAIL PROTECTED] wrote: Should all these three examples give the same result? $ php -r 'var_dump(-1/2*5, 1/-2*5, 1/2*-5);' float(-2.5) float(-0.1) float(-2.5) They should all give -2.5! But I think normal programmers will use braces in such situations... -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php If you use variables, then this works fine ... php -r $a = 1; $b = -2; $c = 5; var_dump($a/$b*$c); float(-2.5) -- - Richard Quadling Zend Certified Engineer : http://zend.com/zce.php?c=ZEND002498r=213474731 Standing on the shoulders of some very clever giants! -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DEV] Re: #41401 [Opn-Bgs]: Order of Operations error on divide by negative
Michael Wallner wrote: [EMAIL PROTECTED] wrote: ID: 41401 Updated by: [EMAIL PROTECTED] Reported By: drlippman at yahoo dot com -Status: Open +Status: Bogus Bug Type: Math related Operating System: Windows, Linux PHP Version: 4.4.7 New Comment: [2007-05-15 15:44:07] drlippman at yahoo dot com Description: Left-to-right order of operations does not appear to be honored when dividing by a negative Reproduce code: --- 1/-2*5 Expected result: -2.5 Actual result: -- -.1 Should all these three examples give the same result? $ php -r 'var_dump(-1/2*5, 1/-2*5, 1/2*-5);' float(-2.5) float(-0.1) float(-2.5) According to my memory of Please My Dear Aunt Sally these should be: -1/2*5 = -.1 1/-2*5 = -.1 1/2*-5 = -.1 So, that is bad if PHP answers that way. Someone please correct me if my memory is wrong. Is there some rule that negative values should be done first before positive values? -- Brian Moon Senior Developer -- http://dealnews.com/ It's good to be cheap =) -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DEV] Re: #41401 [Opn-Bgs]: Order of Operations error on divide by negative
Brian Moon wrote: According to my memory of Please My Dear Aunt Sally these should be: -1/2*5 = -.1 1/-2*5 = -.1 1/2*-5 = -.1 So, that is bad if PHP answers that way. Someone please correct me if my memory is wrong. Is there some rule that negative values should be done first before positive values? My memory was corrected off list. Thanks. Stupid teachers and their mnemonics. But, still, PHP is wrong on 1/-2*5 no? -- Brian Moon Senior Developer -- http://dealnews.com/ It's good to be cheap =) -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DEV] Re: #41401 [Opn-Bgs]: Order of Operations error on divide by negative
Hi Richard, - Original Message - From: Richard Quadling Sent: Wednesday, May 16, 2007 [...] If you use variables, then this works fine ... php -r $a = 1; $b = -2; $c = 5; var_dump($a/$b*$c); float(-2.5) Certainly. :-) The problem seems to be the parser is acting weird as far as precedence goes with 1/-2*5. Matt -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DEV] Re: #41401 [Opn-Bgs]: Order of Operations error on divide by negative
On 16/05/07, Brian Moon [EMAIL PROTECTED] wrote: Michael Wallner wrote: [EMAIL PROTECTED] wrote: ID: 41401 Updated by: [EMAIL PROTECTED] Reported By: drlippman at yahoo dot com -Status: Open +Status: Bogus Bug Type: Math related Operating System: Windows, Linux PHP Version: 4.4.7 New Comment: [2007-05-15 15:44:07] drlippman at yahoo dot com Description: Left-to-right order of operations does not appear to be honored when dividing by a negative Reproduce code: --- 1/-2*5 Expected result: -2.5 Actual result: -- -.1 Should all these three examples give the same result? $ php -r 'var_dump(-1/2*5, 1/-2*5, 1/2*-5);' float(-2.5) float(-0.1) float(-2.5) According to my memory of Please My Dear Aunt Sally these should be: -1/2*5 = -.1 1/-2*5 = -.1 1/2*-5 = -.1 So, that is bad if PHP answers that way. Someone please correct me if my memory is wrong. Is there some rule that negative values should be done first before positive values? I'm in the UK and I was taught (over 35 years ago at least) about BODMAS Brackets Orders Division Multiplication Addition Subtraction. http://en.wikipedia.org/wiki/BODMAS -- Brian Moon Senior Developer -- http://dealnews.com/ It's good to be cheap =) -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php -- - Richard Quadling Zend Certified Engineer : http://zend.com/zce.php?c=ZEND002498r=213474731 Standing on the shoulders of some very clever giants! -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
[PHP-DEV] Re: #41401 [Opn-Bgs]: Order of Operations error on divide by negative
Michael Wallner wrote: Should all these three examples give the same result? ^ n't $ php -r 'var_dump(-1/2*5, 1/-2*5, 1/2*-5);' float(-2.5) float(-0.1) float(-2.5) Sorry, -- Michael -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
