[Year 12 SofDev] Reading the study design

Tue Dec 15 11:50:11 AEDT 2015

In PHP they seem EFFECTIVELY synonymous. 
> In PHP, associative arrays are implemented as hashtables, with a bit of extra functionality.
> 
> However technically speaking, an associative array is not identical to a hashtable - it's simply implemented in part with a hashtable behind-the-scenes. Because most of its implementation is a hashtable, it can do everything a hashtable can - but it can do more, too.
> 
> For example, you can loop through an associative array using a for loop, which you can't do with a hashtable.
> 
> So while they're similar, an associative array can actually do a superset of what a hashtable can do - so they're not exactly the same thing. Think of it as hashtables plus 
> 

From: http://stackoverflow.com/questions/3134296/hash-tables-vs-associative-arrays

Laurie Savage
PVGC

> On 15 Dec 2015, at 11:32 AM, Mark <mark at vceit.com> wrote:
> 
> Thanks, Duane. The interpretation seems to be heading in that direction, even though research is revealing that the concepts are not perfectly synonymous. In researching their differences, I found that associative arrays (a.k.a. a map or dictionary) is an abstract data type (ADT) whereas a hashing table is a concrete data structure. When I got this far <http://cs.stackexchange.com/questions/6678/relation-and-difference-between-associative-array-and-hashing-table> I started backing away v-e-r-y slowly...
> 
> "A dictionary supports Find(x) queries. For an a key x, return the element in the dictionary with key x, if such an element exists. A dynamic dictionary also supports Insert(x) and Delete(x). Common implementations of a dictionary include different kinds of balanced binary search trees (e.g. red black tree) and various kinds of hash tables.
> 
> In addition to Find an ADT may require support of successor(x) queries. That is, maintain a set of keys S, and given key x, find the smallest key t∈S such that s<t. Concrete data structures which support the Successor ADT include various binary search trees, and more complicated structures such as an X-fast trie or van Emde Boas tree (if the keys are integers)."
> 
> Now I just have to squeeze that into a friendly slideshow...
> 
> Cheers
> Mark
> 
> On 15 December 2015 at 11:05, Collinson, Duane A <collinson.duane.a at edumail.vic.gov.au <mailto:collinson.duane.a at edumail.vic.gov.au>> wrote:
> Hi Mark
> 
>  
> I interpreted this as dictionaries and hash tables are synonyms for associative arrays.
> 
>  
> Could see another way of teaching this KK.
> 
>  
> Cheers
> 
>  
> Duane Collinson
> 
>  
> 
> Horsham College
> 
> 310 Baillie Street
> 
> Horsham, Victoria 3400
> 
>  
> 
> (03) 5381 7100
> 
>  
> 
>  
> 
> From: sofdev-bounces at edulists.com.au <mailto:sofdev-bounces at edulists.com.au> [sofdev-bounces at edulists.com.au <mailto:sofdev-bounces at edulists.com.au>] on behalf of Mark [mark at vceit.com <mailto:mark at vceit.com>]
> Sent: Tuesday, 15 December 2015 10:50 AM
> To: Year 12 Software Development Teachers' Mailing List
> Subject: [Year 12 SofDev] Reading the study design
> 
> Maybe someone can help with this, or it might require Paula.
> 
> In SD U4O1 KK2 it refers to "uses of data structures to organise and manipulate data, including associative arrays (or dictionaries or hash tables)"
> 
> I'm not sure how to interpret the 'or's after 'including'. Does it mean"
> - dictionaries and hash tables are synonyms for associative arrays?
> - we may choose between dictionaries and hash tables and associative arrays?
> 
> Neither of those makes much sense.  
> What does it mean in terms of teaching KK?
> 
> Regards
> Mark
> 
> 
> -- 
> 
> Mark Kelly
> 
> mark at vceit.com <mailto:mark at vceit.com>
> http://vceit.com <http://vceit.com/>
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> Mark Kelly
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> mark at vceit.com <mailto:mark at vceit.com>
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