HashTable Class

A HashTable can hold items of any class. It is indexed by any item which supports the hashing function. The usual types of index are as follows:

A hash-table is an array of chains. The hashing function is used to determine which chain the item will appear in -- this chain is then searched to find the item.

The number of chains within a Carapace hash-table is always a power of 2.

HashTable Creation

The create function is used to create a HashTable to have 8 chains:

    (create HashTable 3)

The table can be initailised by supplying an attribute-value list on construction e.g.

    (create HashTable 3 (list (list 1 2) (list 3 4)))

Note that the default number of chains is 8 so the following expression is valid:

    (create HashTable)

HashTable Properties

property name	property type	description
`chains`	Integer	the number of chains within the hash-table -- always a power of 2

HashTable Methods

method name	description
`set`	set an element within the array
`get`	get an element from the array
`resize`	re-size the hash-table by changing its number of chains
`count`	count the number of items within the table -- only items having a value not equal to the empty List `()` are counted
`keys`	return the list of keys from the hash-table -- these are not returned in any particular order
`list`	get all the data from the table as a list of attribute/value pairs
`clear`	remove all data from the hash-table

`set`

Set an element within the hash-table. Any previous value which had the same key is superseded.

Arguments:

key	`Object`
value	`Object`

Return type: the empty List ()

`get`

Get an element from the hash-table. If there is no such key, the empty List () is returned.

Arguments:

key Object

Return type: Object

`resize`

Re-size the hash-table by changing its number of chains. The new number of chains is made to be 2 to the supplied power.

Arguments:

newSize Integer

Return type: the empty List ()

`count`

Count the number of items within the table -- only items having a value not equal to the empty List () are counted.

Arguments: none

Return type: Integer

`keys`

Return the list of keys from the hash-table -- these are not returned in any particular order.

Arguments: none

Return type: List

`list`

Get all the data from the table as a list of attribute/value pairs.

Arguments: none

Return type: List

`clear`

Remove all data from the hash-table.

Arguments: none

Return type: the empty List ()

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