keys in a hash table (aka, all assigned indices in an array): awful hack

*To*: mathgroup at smc.vnet.net*Subject*: [mg13281] keys in a hash table (aka, all assigned indices in an array): awful hack*From*: Daniel Reeves <dreeves at flip.eecs.umich.edu>*Date*: Fri, 17 Jul 1998 03:18:30 -0400*Organization*: University of Michigan EECS*Sender*: owner-wri-mathgroup at wolfram.com

suppose I make some assignments like this: fruits[apple]= crunchy fruits[lemon]= sour I'm treating fruits like a hash table and now I would like a list of all the keys. In this case {apple,lemon}. It seems like there should be an easy way to do this. All I came up with was the following hack: keys[hash_]:= DownValues[hash] /. {RuleDelayed->(#&), hash->(#&)} //ReleaseHold the hash values will be simple; we can just do fruits/@keys[fruits] Thanks, Daniel -- Daniel Reeves dreeves at umich.edu http://interlabs.bradley.edu/~daniel "Computer Science is no more about computers than astronomy is about telescopes." -- E W Dijkstra