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HASH_INIT

HASH_INIT

Name


      HASH_INIT

Purpose


      Initialize a hash table.

Category


Calling Sequence


      hash_init

Inputs


Keyword Parameters


Keywords


        KEY=key Input string array of keys.
        VAL=val Input string array of values.
        N_MAIN=nm Input number of entries in the main table.
        N_OVER=no Input number of entries in the overflow table.
        HASH=h Returned hash table in a structure.
        COLLISIONS=ncoll Returned number of collisions on set up.

Outputs


Common Blocks


Notes


      Notes: User must also provide a hash function which takes
        one key and converts it to an index into the hash table.
        This hash function must be called hash_f and take a single
        string arg (the key) and return a long int (the index into
        the hash table). A default hash function will be used
        unless the user hash function is found on the IDL path
        first (or is compiled). The default hash function just
        sums the ascii codes of the letters in the key and does
        mod 6000 (so make n_main be 6000 if using the default
        hash function. Try n_over=100 or so and check # of
        collisions to see how close, or check h.next).
          A hash table allows a value to be looked up based on a
        given text string, the key. This version of hash_init
        uses strings for both the keys and values (can be
        generalized later).

Modification History


      R. Sterner, 2004 Mar 29
  Copyright (C) 2004, Johns Hopkins University/Applied Physics Laboratory
  This software may be used, copied, or redistributed as long as it is not
  sold and this copyright notice is reproduced on each copy made. This
  routine is provided as is without any express or implied warranties
  whatsoever. Other limitations apply as described in the file disclaimer.txt.



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