Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2012

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: How best to implement a hash table in Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg125121] Re: How best to implement a hash table in Mathematica
  • From: Joseph Gwinn <joegwinn at comcast.net>
  • Date: Wed, 22 Feb 2012 05:33:15 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <jho21j$5sb$1@smc.vnet.net> <jhqmrr$fbq$1@smc.vnet.net> <jhstsv$nk0$1@smc.vnet.net> <jhvuoi$891$1@smc.vnet.net>

In article <jhvuoi$891$1 at smc.vnet.net>,
 Szabolcs Horvát <szhorvat at gmail.com> wrote:

> On 2/20/2012 9:48 AM, Joseph Gwinn wrote:
> >
> > The reason to initialize the hashtable in advance is so a later probe to
> > an empty table element yields {}, versus repeating the question back.
> >
> >
> 
> I probably don't understand your question completely, but why can't you 
> just make definition like
> 
> hashtable[_] = {}
> 
> ?  This will ensure that {} is returned for "undefined" keys.

I'll have to try this and related approaches, but it's not the entire 
hashtable that's empty, it's this or that element of said hashtable.


> Also, please avoid using symbols that start with a capital letter. 
> HashTable is a built-in symbol and if you define it (as you did in the 
> example code you sent), it is likely to break stuff.

Well, I use initial (and embedded) caps all the time, for readable 
symbols, and Mathematica does sometimes balk, so I make the symbol a word 
longer.  

As for HashTable, Mathematica complained, so I changed it to BigHashTable, and 
peace was restored.

Joe Gwinn



  • Prev by Date: Retrieving numerical value for ImagePadding
  • Next by Date: Re: Binning data points
  • Previous by thread: Re: How best to implement a hash table in Mathematica
  • Next by thread: Re: How best to implement a hash table in Mathematica