On 6/21/05, Jochem Maas <jochem@xxxxxxxxxxxxx> wrote: > Dotan Cohen wrote: > > I've got an array $items which has about 200 entires. I want to print > > it might be helpful to know where the array comes from. > or maybe its a static definition to start with (nothing wrong with that as such :-) > does $items change over time? in what way? > > > them out in random order, but as usual, I have a catch! I need to add > > a 'key' so that if need be, I can always return to the same 'random' > > order, like so: > > > > $items=predicatable_random($items, "qwerty"); > > the problem is persistence, if you want a random order that doesn't change > then you have to create the random order, and then store an index for it > somewhere. it may be feasable to either serialize the result and read it from disk > when needed, or store a list of keys (an index of sorts) in file/db and > use that to perform an ordering as required. > > > > > so for each place that I need the items rearranged, I will replace > > qwerty with a different string, and get a different 'random' order. I > > haven't played around with it much as I stumbled into a brick wall > > fairly early and can't get much going. Any ideas? > > > > I tried to play with usort, uksort, ksort, and various combinations > > with shuffle. The 'randomization' can be based on qualities of each > > string, such as 'sort alphebetically by the 7th character', so I > > thats not random. maybe the 'key' you need to pass is > a callback function whose job it is to produce a replicable > (or random for that matter!) ordering somehow - depending on the > complexity of the calculation and size of the dataset you may > need to cache (look at http://php.net/mt_srand if you need predictable > [psuedo]randomness without cacheing (using 'fixed' seeds), and check > the usernotes on http://php.net/shuffle also). e.g: > > $items = array( > /* |--char 7 */ > "cherries", > "bananas", > "orangejuice", > "red apples", > "smelly fish", > "more bananas", > "ship full of bananas", > "tarantula", > "poisoned apple", > /* |--char 7 */ > ); > > function permaRandom($items, $callback) > { > /* caching left as an exercise to the reader ;-/ */ > if (is_callable($callback)) { > $items2 = /*($yes = gotcachedpermarandom($callback)) > ? getfromcache($callback) > : */call_user_func($callback, $items); > /* if ($yes) storeincache($callback, $items2); */ > } > > return $items2; > } > > function sortAlphaChar7Random($items) > { > $keys = $items2 = array(); > // assumption made that $item is a string > // and at least 7 chars long, oh and spaces > // wont do much good for the sorting probably.. > foreach ($items as $k => $item) { > $keys[$k] = @$item{7}; > } > asort($keys, SORT_LOCALE_STRING | SORT_STRING); > foreach ($keys as $k => $v) { > $items2[] = $items[$k]; > } > return $items2; > } > > var_dump(permaRandom($items, "sortAlphaChar7Random"), > permaRandom($items, "sortAlphaChar7Random"), > permaRandom($items, "sortAlphaChar7Random")); > > > thought that I'd try that, but I got lost in explodes and such. > > > > Thanks all. I always look forward to my php lessons! > > > > Dotan > > http://english-lyrics.com/el/index.php > > Song Lyrics > > > > $items is a static file, that does not change over time. It just needs to be output in a reproducable 'random' order for different purposes. I looked over your suggested fuctions, but decided to try Marek's simpler seed solution first. And it worked for what I need, so I will be going that route. But I very much appreciate your insight. Although complicated, it presents a different way of solving the same problem. That in itself is interesting. I intend to play with it a little when I have some more time. Maybe I will find an advantage in your solution that I may need some day! Thank you. Dotan http://english-lyrics.com/ Song Lyrics -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
