RE: [PHP-WIN] Random Code

Just realized a serious problem with this approach: it will, due to its nature, run very quickly towards +oo ... hence it is not proper to implement as a computer program. >-----Original Message----- >From: Svensson, B.A.T. [mailto:B.A.T.Svensson@lumc.nl] >Sent: Tuesday, January 23, 2001 9:10 PM >To: L4@di1.net; php-windows@lists.php.net >Subject: RE: [PHP-WIN] Random Code > > >If one need to create multiple numbers per second (that is >cal;culation time >is critical), then I would suggest, in accordance to my >previous letter, >that one should pick a functions that is guaranteed to be constantly >growing, that is that the property "x1>x2 -> f(x1)>f(x2)" >always will hold >true for the function f. If this is the case, then the f will >be able to >produce input values for a mapping function that can be guaranteed to >produce unique numbers. > > >>-----Original Message----- >>From: Larry Forrister [mailto:L4@stetson.net] >>Sent: Tuesday, January 23, 2001 7:26 PM >>To: php-windows@lists.php.net >>Subject: Re: [PHP-WIN] Random Code >> >> >>Do you mean W3E4-22ER would be valid? If so there would be 36^8 >>(2,821,109,907,456) possible values. >> >>A truly random generator algorithm cannot guarantee uniqueness. I'm >>guessing what you want is to generate each possible value once in a >>pseudo-random order. Would just apparent randomness suffice? >> >>With what frequency do the values need to be generated? Once >every few >>seconds/minutes or multiple times per second? >>~~LF >> >> >>Sigurd Magnusson wrote: >> >>> Whats the best way to make a completely random, unique code in the >>> format "ABCD-1234" where each of the 8 characters can be >alphanumerc; >>> 0-9,A-Z... I thought about generating a 36^4 number, >converting to to >>> base '36', and repeating the process. What's a good way to >ensure the >>> code is not repeated, though? >>> >>> Siggy >> >>-- >>PHP Windows Mailing List (http://www.php.net/) >>To unsubscribe, e-mail: php-windows-unsubscribe@lists.php.net >>For additional commands, e-mail: php-windows-help@lists.php.net >>To contact the list administrators, e-mail: >>php-list-admin@lists.php.net >> > >-- >PHP Windows Mailing List (http://www.php.net/) >To unsubscribe, e-mail: php-windows-unsubscribe@lists.php.net >For additional commands, e-mail: php-windows-help@lists.php.net >To contact the list administrators, e-mail: >php-list-admin@lists.php.net >