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 >