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From: thomasw@hpcupt1.cup.hp.com (Thomas Wang)
Newsgroups: comp.lang.c
Subject: how to write hash function for double
Message-ID: <67790003@hpcupt1.cup.hp.com>
Date: 18 Jun 91 19:07:22 GMT
Organization: Hewlett Packard, Cupertino
Lines: 23


I want to write a hash function for C double floating point number.
I can either convert the double to string, then hash the string value.
Or I can just scramble the bits contained in the double number.

The question is whether there can be two different bit patterns of double
that represented the same double number?

double a;
double b;

...

if ((a == b) && (memcmp(&a, &b, sizeof(double)) != 0))
{
   printf("help!\n"); /* can this ever happen in Ansi-C ? */
}


 -Thomas Wang
              (Everything is an object.)
                                                     wang@hpdmsjlm.cup.hp.com
                                                     thomasw@hpcupt1.cup.hp.com