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