J's dictionary data type is probably the locale.
http://www.jsoftware.com/pipermail/programming/2014-February/035615.html
has a list of urls documenting locales.
That said, note that names within locales have syntactic limits. So
you'd have to map your identifier into something suitable as a name.
This process is analogous to hashing or to numeric base conversion.
For example:
thru=: [ + 1 i.@+ -~
10 thru 20
10 11 12 13 14 15 16 17 18 19 20
alph=: a.&i.
alph 'az'
97 122
NB. say this with a guido sarducci accent:
thrua=: thru&.alph
'a' thrua 'z'
abcdefghijklmnopqrstuvwxyz
namechars=: '_',('a' thrua 'z'),('A' thrua 'Z'),'0' thrua '9'
num2name=: [ , namechars {~ (#namechars) #.inv ]
'prefix' num2name 8675309
prefixHQVt
The prefix prevents accidental collisions with other names within the
locale, if you need that.
So if we want a dictionary with numeric keys (which could instead have
been a sparse array), we might use:
dictname=: ('z' num2name ]) , '_', [ ,'_'"_
setdict=:1 :0
:
(m dictname x)=: y
)
getdict=: ".@dictname
123 'example' setdict |:i.3 2
0 2 4
1 3 5
'example' getdict 123
0 2 4
1 3 5
So anything that you can convert to a nonnegative integer can be used
as dictionary key with a system like this.
Obviously, though, other systems are possible. (For example, you
could use a sparse array instead of a locale, that will give you
different performance characteristics.)
And I see Pascal Jasmin has just now posted a similar proposal, so
I'll stop here - I really have some other tasks I need to get done.
Thanks,
--
Raul
On Mon, Mar 3, 2014 at 10:06 AM, Yike Lu <yikelu.h...@gmail.com> wrote:
> A tangential but related question: does J have a dictionary data type?
> Where can I read about it?
>
> Thanks.
>
>
> On Mon, Mar 3, 2014 at 8:55 AM, Tracy Harms <kalei...@gmail.com> wrote:
>
>> My naïve intuition is that a tree of symbols would be the most direct route
>> to increased performance. Would that fit with what you suggested here,
>> Raul?
>> On Mar 3, 2014 1:52 AM, "Raul Miller" <rauldmil...@gmail.com> wrote:
>>
>> > We should be able to concatenate boxed arrays with somewhat better
>> > performance. Conceptually speaking, the added box can be treated as an
>> > opaque string (other than reference counting bumps) for the purpose of
>> the
>> > concatenation operation. Conceptually, also, already have some way of
>> > allocating memory in "power of two sized blocks". But memory management
>> is
>> > a subtle thing, so maybe there is something I am missing?
>> >
>> > Thanks,
>> >
>> > --
>> > Raul
>> >
>> >
>> > On Mon, Mar 3, 2014 at 12:26 AM, bill lam <bbill....@gmail.com> wrote:
>> >
>> > > I would be quite happy if J can do that in a few minutes. The
>> > > bottle neck is not string related but J converts Json data into a
>> > > box array. Because concatenation of box arrays cannot be done
>> > > in place, it re-constructs a new box array for each node and this
>> > > is quadratic.
>> > >
>> > > Even if you can use python to parse json, it will still take a
>> > > quadratic operation to convert that parsed data structure
>> > > back to a J box array. Untested.
>> > >
>> > > Пн, 03 мар 2014, June Kim (김창준) писал(а):
>> > > > Hello,
>> > > >
>> > > > I recently tried to work on a JSON file (a bookmark file from Chrome
>> > > > browser), which is about 28MB. My initial attempt was using the json
>> > > parser
>> > > > from the J packages. Oh, it was slow. It took more than one minute on
>> > my
>> > > > machine.
>> > > >
>> > > > Disappointed, but I was kind of expecting the slow performance
>> because
>> > > > string and tree are not what J's strength is.
>> > > >
>> > > > Now I turned to Python and tried parsing the file using the standard
>> > > > package. Oh, I took about a second.
>> > > >
>> > > > So I can proceed with Python but I want to know if there are any
>> other
>> > > > options working with J with better performance.
>> > > >
>> > > > June
>> > > >
>> ----------------------------------------------------------------------
>> > > > For information about J forums see
>> http://www.jsoftware.com/forums.htm
>> > >
>> > > --
>> > > regards,
>> > > ====================================================
>> > > GPG key 1024D/4434BAB3 2008-08-24
>> > > gpg --keyserver subkeys.pgp.net --recv-keys 4434BAB3
>> > > gpg --keyserver subkeys.pgp.net --armor --export 4434BAB3
>> > > ----------------------------------------------------------------------
>> > > For information about J forums see http://www.jsoftware.com/forums.htm
>> > >
>> > ----------------------------------------------------------------------
>> > For information about J forums see http://www.jsoftware.com/forums.htm
>> ----------------------------------------------------------------------
>> For information about J forums see http://www.jsoftware.com/forums.htm
>>
> ----------------------------------------------------------------------
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