Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!edcastle!aiai!ken
From: ken@aiai.ed.ac.uk (Ken Johnson)
Newsgroups: comp.lang.c
Subject: Random long-number generator
Summary: shift one left 16 bits, add another one.
Keywords: random maxint
Message-ID: <1486@skye.ed.ac.uk>
Date: 21 Dec 89 16:18:54 GMT
References: <83943@linus.UUCP>
Reply-To: ken@aiai.UUCP (Ken Johnson)
Followup-To: comp.lang.c
Organization: AIAI, University of Edinburgh, Scotland
Lines: 21

In article <83943@linus.UUCP> rtidd@mwsun.mitre.org writes:

# I was trying to generate a random number bewteen 0 and maxlongint (i.e. 
# 2^32) on my machine (80386 with Interactive).  The rand() function that
# I have returns a psuedo-random number between 0 and MAXINT (which in
# this case is 32768).  Does anyone have any ideas or any code that
# generates random numbers, or anyplace that I can check to find such
# code?

Suppose you have two random numbers, int r1 and int r2, each
chosen so as to lie randomly between 0x0000 and 0xFFFF.  Then

	long r;
	r = ((long) r1 << 16) | ((long) r2) & 0x0000FFFFL);

-- Ken
-- 
Ken Johnson, AI Applications Institute, 80 South Bridge, Edinburgh EH1 1HN
E-mail ken@aiai.ed.ac.uk, phone 031-225 4464 extension 212
`I have read your article, Mr Johnson, and I am no wiser now than when I
started'.  -- `Possibly not, sir, but far better informed.'