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digitalmars.D - Static associative arrays?

reply Gregor Richards <Richards codu.org> writes:
It would be nice to have a static associative array syntax analogous to 
the static array syntax. Something like this perhaps:

char[][char[]] a = [ "a" : "Apple", "b" : "Banana", "c" : "Cantelope", 
... ];

This syntax is unambiguous (though admittedly complex) even for 
arbitrarily complex AAs:

char[int][char[][char[]]] a = [ [ "a" : "b", "c" : "d" ] : [ 0 : 'e', 1 
: 'f' ] ];

It also has the added advantage of being similar to the static struct 
syntax.


To be honest, I don't need static associative arrays desperately, but I 
also don't think I need to explain why it would be useful.

  - Gregor Richards
Feb 15 2007
next sibling parent Derek Parnell <derek psych.ward> writes:
On Thu, 15 Feb 2007 23:07:54 -0800, Gregor Richards wrote:


 It would be nice to have a static associative array syntax analogous to 
 the static array syntax. Something like this perhaps:
 
 char[][char[]] a = [ "a" : "Apple", "b" : "Banana", "c" : "Cantelope", 
 ... ];
 
 This syntax is unambiguous (though admittedly complex) even for 
 arbitrarily complex AAs:
 
 char[int][char[][char[]]] a = [ [ "a" : "b", "c" : "d" ] : [ 0 : 'e', 1 
: 'f' ] ];
 
 It also has the added advantage of being similar to the static struct 
 syntax.
 
 
 To be honest, I don't need static associative arrays desperately, but I 
 also don't think I need to explain why it would be useful.


I still prefer then syntax ...


 char[][char[]] a = [ "a" = "Apple", "b" = "Banana", "c" = "Cantelope", 
 ... ];
 
 
 char[int][char[][char[]]] a = [ [ "a" = "b", "c" = "d" ] = [ 0 = 'e', 1 
= 'f' ] ];

because the '=' makes it more obvious what data is being assigned to which
key.


-- 
Derek Parnell
Melbourne, Australia
"Justice for David Hicks!"
skype: derek.j.parnell
Feb 16 2007
prev sibling next sibling parent reply Serg Kovrov <kovrov no.spam> writes:
Gregor Richards wrote:

 It would be nice to have a static associative array syntax analogous to 
 the static array syntax. Something like this perhaps:
 
 char[][char[]] a = [ "a" : "Apple", "b" : "Banana", "c" : "Cantelope", 
 ... ];
 
 This syntax is unambiguous (though admittedly complex) even for 
 arbitrarily complex AAs:
 
 char[int][char[][char[]]] a = [ [ "a" : "b", "c" : "d" ] : [ 0 : 'e', 1 
 : 'f' ] ];
 
 It also has the added advantage of being similar to the static struct 
 syntax.


Yep, what we need, is sort of 'AA Literals' which can be used to 
initialize either static or dynamic associative array.

-- 
serg.
Feb 18 2007
parent reply Dan <murpsoft hotmail.com> writes:
 Yep, what we need, is sort of 'AA Literals' which can be used to 
 initialize either static or dynamic associative array.
 
 -- 
 serg.


Well, currently dynamic arrays are initialized by dup'ing a static array, or by
assigning one thing at a time (ick).

Associative Arrays should be no different really.  I think the issue with this
is that the hash function he's using runs on pointers, which means you can't
build the hashtables until runtime and therefore can't have static associative
arrays without changes.  Am I correct?

For my needs (small associative arrays as objects), I would prefer not to use
hashing, and instead use a median-left, low-left binary search array (x << 1
goes left, x << 1 + 1 goes right, and cache stays coherent.)  The plan was to
again use the char[] structs (not the actual strings) I'm going to look into
what I can do to override Associative Arrays in D.

On that note, has anyone found evidence of a median-left low-left binary search
array?  I think (currently) I may be the first to use such a device, in spite
of it's obviousness?  I'd love to hear evidence otherwise.

Thanks,
Dan
Mar 14 2007
next sibling parent Dan <murpsoft hotmail.com> writes:
 I think the issue with this is that the hash function he's using runs on
pointers, which means you can't build the hashtables until runtime and
therefore can't have static associative arrays without changes.  Am I correct?


Walter?
Mar 15 2007
prev sibling next sibling parent Manfred Nowak <svv1999 hotmail.com> writes:
Dan wrote


 I'd love to hear evidence otherwise. 


It's well known

http://commons.wikimedia.org/wiki/Image:Binary_tree_in_array.svg

-manfred
Mar 15 2007
prev sibling parent Stewart Gordon <smjg_1998 yahoo.com> writes:
Dan Wrote:
<snip>

 Associative Arrays should be no different really.  I think the 
 issue with this is that the hash function he's using runs on 
 pointers, which means you can't build the hashtables until 
 runtime and therefore can't have static associative arrays 
 without changes.  Am I correct?


<snip>

But it should still work on built-in types.  Moreover, even if for a given type
doing it at compiletime doesn't work, it could generate a module constructor
that does the initialisation.

Stewart.
Mar 16 2007
prev sibling parent Dan <murpsoft hotmail.com> writes:
Manfred Nowak Wrote:

 It's well known
 
 http://commons.wikimedia.org/wiki/Image:Binary_tree_in_array.svg


Sweet.  Thanks.  I couldn't find it through all the references to binary trees
with Nodes and Node*'s, and median-median binary search arrays.

I had the same problem of reinventing the wheel with jump tables.
Mar 16 2007