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hash_32bit [2007/03/02 02:32] (current)
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 +# $EPIC: hash_32bit.txt,​v 1.3 2007/03/02 02:32:04 jnelson Exp $
 +======Synopsis:​======
 +$__hash_32bit__(<​word>​ <​length>​)
 +
 +======Technical:​======
 +   * The <​word>​ and <​length>​ arguments are [[what is a word|dwords]],​ which is different from most function arguments.
 +   * If the <​word>​ argument is omitted the empty string is returned
 +   * If the <​length>​ argument is omitted it defaults to 0
 +   * If the <​length>​ argument is a negative number of is greater than 64, it is changed to 20.
 +   * The return value of this function is a 32 bit signed integer that is a "​hash"​ of the first <​length>​ characters in <​word>​.
 +   * Analytically speaking, hashing is a specific type of lossy compression.
 +   * All lossy compression techniques suffer from "​collisions"​. ​ A collision occurs when two different <​word>​s yield the same return value. ​ If you must avoid collisions, use $[[encode]]() instead.
 +   * The inverse of this principle is that all lossy compression techniques are irreversible. ​ You cannot take the return value of this function and determine what <​word>​ was.  If you must be able to recreate <​word>,​ use $[[encode]]() instead.
 +   * The return value of this function is deterministic within the lifetime of the client. ​ The algorithm used to compute this value is subject to change in the future; you should not "​save"​ the return value of this function to a file for use in future versions in epic.
 +
 +======Practical:​======
 +You can use $__hash_32bit__() to convert an arbitrary string (perhaps
 +containing characters that cannot be used in alias names) into a 32 bit signed
 +integer value which you can use as part of an alias name. Collisions will
 +occur. ​ You cannot recover the original <​word>​ from the output of this
 +function. ​ Please keep these in mind when using this function.
 +
 +======Returns:​======
 +A 32 bit signed integer (it can be either negative or positive) that 
 +is deterministically derived from the first <​length>​ characters in <​word>​.
 +
 +======Examples:​======
 +$hash_32bit("​hello there"​) returns 51439
  
hash_32bit.txt ยท Last modified: 2007/03/02 02:32 (external edit)