FunctionPackage: exclToCDocOverviewCGDocRelNotesFAQIndexPermutedIndex
Allegro CL version 10.1
Unrevised from 10.0 to 10.1.
10.0 version


Arguments: int

Returns a positive fixnum suitable for a hash-table size greater than or equal to int, which should be a fixnum. With all fixnums below the limit, the value returned will be a prime number. The value is returned from a table, so the calculation is fast. For fixnums above the limit, the value returned is at least not divisible by 2, 3, 5, or 7. Results lose accuracy as they approach most-positive-fixnum.


Limits are approximate, and may change in the future. Currently:


Not all prime numbers are returned. The prime number table is populated with an approximately 2% increment, so the difference between one result and the next possible result (for values of int under the limit) are approximately 2% apart:

cl-user(1): (excl:hash-primify 100000000)
cl-user(2): (excl:hash-primify (1+ *))
cl-user(3): (float (/ * **))

There may be other prime numbers not returned by this function; but because it is the goal of this function to quickly return a size suitable for efficient hash-table operation, populating all primes is not necessary.

Copyright (c) 1998-2022, Franz Inc. Lafayette, CA., USA. All rights reserved.
This page was not revised from the 10.0 page.
Created 2019.8.20.

Allegro CL version 10.1
Unrevised from 10.0 to 10.1.
10.0 version