Bernard Poulin wrote:
I cannot say for AS3 implementation because I never tried it. (Which
is the
original subject of this topic.)
In AS1, AS2 and javascript, I am pretty sure that all objects (including
Arrays) are key/value maps. (i.e. Associative arrays)
http://en.wikipedia.org/wiki/Associative_array#JavaScript
It is very possible that the internal implementation is not a "hashmap",
but I still think it is a highly efficient map of some sort because
this is
so central to the language.
I would hope that it is efficient but hashing adds a lot of overhead and
wasted space for small arrays and really needs to be tuned to get the
desired results for larger arrays.
If the arrays are stored in sorted order, then the normal key lookup can
be done as a binary lookup which will be a lot quicker than an
exhaustive search. The price is paid when a new associative entry is added.
Nothing is free.
None of my work has required has involved large associative arrays where
hashing would add a significant improvement in speed but it would be
nice to have such a class available for those who need it.
In the early days (1960s) when I was taking Computer Science at
University, we spent a lot of time worrying about these things since
memory was scarce (64K word (36 bits per word) computer cost a million
dollars and supported 16 users) and CPU speeds where not very fast (a
1MIP computer was state of the art).
If really had to look carefully at how things got stored and retrieved,
it you had a large number of them.
...at least this is what I think. I might be completely wrong.
B.
2006/5/12, Ron Wheeler <[EMAIL PROTECTED]>:
I would be a little surprised. There does not seem to be any way to
control the hash parameters and every array would have a lot of wasted
space for nothing and without any way to control the hash size and the
percent utilization, you would not get a lot of advantage for the big
arrays.
The Java HashMap defaults are pretty modest and would yield less than
optimal performance with a big array.
You can set the parameters if you have a big array and know a bit about
the "randomness" of your keys to get fast lookups with a reasonable
trade-off in wasted space
Perhaps someone who knows the Flash Player internals could tell for
sure.
Ron
Bernard Poulin wrote:
> mmm... Are you implying that ActionScript objects are not hashmaps?
> I thought they were *all* hashmaps (even Arrays are hashmaps). Every
> method
> call that you do involves at least one hash lookup.
>
> B.
>
> 2006/5/10, Ron Wheeler <[EMAIL PROTECTED]>:
>>
>> It appears that a HashMap is a Java class that uses a hash on the
"key"
>> to store its keys and values.
>> http://java.sun.com/j2se/1.4.2/docs/api/java/util/HashMap.html
>> This would speed up lookup if you have a large set of keys.
>> If you do not need the speed or do not have a large collection of
keys
>> to store, an array object would seem to give the same
functionality in
>> ActionScript.
>> This leaves the implementation of the array to Flash and it is
likely a
>> simple structure that has to be searched sequentially (by the
Flash VM)
>> to get the associated value.
>>
>> It you really need a hashing array that can handle large numbers of
>> key/value pairs, you probably have to write one. This is an old
concept
>> and you can likely find a few design ideas and probably some code if
you
>> search for it.
>>
>> If you are converting code and want to create a HashMap class that
has
>> the same methods as HashMap in Java, you could fake the internal
storage
>> technology with a simple Array. it would be faster for a small set of
>> values and would get a bit slower as the number of keys increased.
>> You could start with a dumb HashMap class and then make it a true
>> hashing data store later without having to rewrite your code.
>> HashMap was only added to Java in Java 1.1 and they lived without it
>> before then.
>>
>> Ron
>>
>> Joshua Graham wrote:
>> > Bit strange, but that works, thanks.
>> >
>> > Joshua
>> >
>> > On 10 May 2006, at 12:06, Lee McColl-Sylvester wrote:
>> >
>> >> Well, in AS2, it's called an object ;)
>> >>
>> >> Lee
>> >>
>> >>
>> >>
>> >> -----Original Message-----
>> >> From: [EMAIL PROTECTED]
>> >> [mailto:[EMAIL PROTECTED] On Behalf Of
>> Joshua
>> >> Graham
>> >> Sent: 10 May 2006 11:19
>> >> To: [email protected]
>> >> Subject: [Flashcoders] HashMap?
>> >>
>> >> Is there an AS3 equivalent of the java HashMap?
>> >>
>> >> Basically, I just need the ability to set key/value pairs quickly/
>> >> easily.
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>> >
>> >
>> >
>>
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