Module description

hct -- Hash Cell Table

The hct module implements a hash table that stores cell wide data.

Hash table structure

hct% ( -- n )

Get the required space for a hash table variable

Hash table creation, initialisation and destruction

hct-init ( u hct -- )

Initialise the hash table with an initial size u

hct-(free) ( hct -- )

Free the nodes from the hash table

hct-create ( u "<spaces>name" -- ; -- hct )

Create a named hash table with an initial size u in the dictionary

hct-new ( u -- hct )

Create a hash table with an initial size u on the heap

hct-free ( hct -- )

Free the hash table from the heap

Module words

hct+hash ( c-addr1 u1 -- u2 )

Calculate the hash value of a key

Member words

hct-empty? ( hct -- flag )

Check if the table is empty

hct-length@ ( hct -- u )

Get the number of nodes in the table

hct-load@ ( hct -- u )

Get the load factor [*100%]

hct-load! ( u hct -- )

Set the load factor [*100%]

hct-size! ( u hct -- )

Resize the hash table to size u

Hash table words

hct-insert ( x c-addr u hct -- )

Insert cell data x with the key c-addr u in the table

hct-delete ( c-addr u hct -- false | x true )

Delete the key c-addr u from the table, return the cell data related to the key

hct-get ( c-addr u hct -- false | x true )

Get the cell data x related to the key c-addr u from the table

hct-has? ( c-addr u hct -- flag )

Check if the key c-addr u is present in the table

Special words

hct-count ( x hct -- u )

Count the number of occurrences of the cell data x in the table

hct-execute ( i*x xt hct -- j*x )

Execute xt for every key and cell data in table

hct-execute? ( i*x xt hct -- j*x flag )

Execute xt for every key and cell data in table or until xt returns true, flag is true if xt returned true

Inspection

hct-dump ( hct -- )

Dump the hash table

Examples

\ ==============================================================================
\
\          hnct_expl - the cell hash table example in the ffl
\
\               Copyright (C) 2007  Dick van Oudheusden
\  
\ This library is free software; you can redistribute it and/or
\ modify it under the terms of the GNU General Public
\ License as published by the Free Software Foundation; either
\ version 2 of the License, or (at your option) any later version.
\
\ This library is distributed in the hope that it will be useful,
\ but WITHOUT ANY WARRANTY; without even the implied warranty of
\ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
\ General Public License for more details.
\
\ You should have received a copy of the GNU General Public
\ License along with this library; if not, write to the Free
\ Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
\
\ ==============================================================================
\ 
\  $Date: 2008-03-11 18:33:47 $ $Revision: 1.4 $
\
\ ==============================================================================

include ffl/hct.fs
include ffl/hci.fs

\ Example: store mountain heights in a hash table


\ Create the hash table in the dictionary with an initial size of 10

10 hct-create height-table


\ Add the mountains (in meters)

8300 s" mount everest" height-table hct-insert
4819 s" mont blanc"    height-table hct-insert
5642 s" mount elbrus"  height-table hct-insert

\ Get a mountain height

s" mount everest" height-table hct-get [IF]
  .( Mount everest: ) . cr
[ELSE]
  .( Unknown mountain) cr
[THEN]

s" vaalserberg" height-table hct-get [IF]
  .( Vaalserberg: ) . cr
[ELSE]
  .( Unknown mountain) cr
[THEN]


\ Word for printing the mountain height

: height-emit ( n c-addr u -- = height key )
  type ."  -> " . cr
;


\ Print all mountain heights

' height-emit height-table hct-execute            \ Execute the word height-emit for all entries in the hash table



\ Example hash table iterator

\ Create the hash table iterator in the dictionary

height-table hci-create height-iter               \ Create an iterator named height-iter on the height-table hash table

\ Moving the iterator

height-iter hci-first                         \ Move the iterator to the first record
[IF]                                          \ If record exists Then ..
  height-iter hci-key type                    \   Type the key ..
  .(  => )
  .                                           \   .. and the value
  cr
[THEN]

8300 height-iter hci-move                     \ Move the iterator to the mountain with a height of 8300
[IF]                                          \ If mountain exists Then ..
  height-iter hci-key type                    \   Type the name ..
  .(  => )
  height-iter hci-get drop .                  \   .. and the height
  cr
[ELSE]
  .( No mountain found with a height of 8300) cr  
[THEN]

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