Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!willett!ForthNet
From: ForthNet@willett.UUCP (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Experimental Ideas
Message-ID: <263.UUL1.3#5129@willett.UUCP>
Date: 14 Jan 90 16:07:44 GMT
Organization: Latest Link in ForthNet Chain (Pittsburgh, PA)
Lines: 24

Category 3,  Topic 5
Message 27        Sun Jan 14, 1990
P.SNYDER1                    at 04:27 PST
 
Subject: DSQRT > I need to take the square root of a number ranging from 0 -
>1,596,801,600. This isn't fast, but it's simple and it works: Single
precision: 
  : isqrt ( n--sqrt.of.n)       \ integer square root
    0   1                       ( n r d)  \ number, root, decrementor
    begin rot over - dup 0>=    ( r d n' flg) 
    while rot 1+   rot 2+       ( n' r' d') 
    repeat 2drop 
  ;  This works by subtracting consecutive odd numbers from n till n<0.  Since
sums of consecutive odds equal consecutive squares, the number  of
subtractions equals the square root.  Here's the double precision version:  :
dsqrt ( dn--root)             \ dn is double, root is a single 
  0 0     1 0 
  begin 2rot 2over d- 2dup 0 0 d< not 
  while 2rot 1 0 d+   2rot 2 0 d+ 
  repeat 2drop 2drop  ; 
                                         ......paul
-----
This message came from GEnie via willett through a semi-automated process.
Report problems to: 'uunet!willett!dwp' or 'willett!dwp@gateway.sei.cmu.edu'