Path: utzoo!attcan!uunet!willett!ForthNet
From: ForthNet@willett.UUCP (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Data Structures
Message-ID: <1097.UUL1.3#5129@willett.UUCP>
Date: 8 Jun 90 04:08:30 GMT
Organization: Latest link in the ForthNet chain.  (Pgh, PA)
Lines: 52


 Date: 06-06-90 (10:48)              Number: 3324 (Echo)
   To: ALL                           Refer#: NONE
 From: CHARLIE HITSELBERGER            Read: (N/A)
 Subj: PRIME NUMBERS                 Status: PUBLIC MESSAGE

 I was just sort of messing around the other day, trying to write a
 primes generator in Forth83.  Here's what I came up with:

 2VARIABLE NUMER  3. NUMER 2!
 VARIABLE DENOM
 : PRIMES   ( -- ) CR
     BEGIN   3 DENOM !  FALSE
         BEGIN
             DROP  NUMER 2@  DENOM @
             UM/MOD DROP  DUP
             IF
                 DENOM @ DUP M*
                 NUMER 2@  D>
                 2 DENOM +!
             ELSE
                 TRUE
             THEN
         UNTIL
         IF
             NUMER 2@  20 D.R
         THEN
         NUMER 2@  2 M+  NUMER 2!
         ?TERMINAL
     UNTIL
 ;

 here's the BASIC equivalent:
 10 N=3
 20 D=3
 30 IF N/D>INT(N/D) THEN 50
 40 N=N+2:GOTO 20
 50 IF D*D<N THEN D=D+2:GOTO 30
 60 PRINT N,:GOTO 40

 Is my method a pretty "elegant" approach?  What does the standards
 committee think that "1000000. 3 UM/MOD" is supposed to leave on the
 stack?  I'd leave a "1 65535" myself (the modulo and an overflow flag). 
 Of course, my implementation doesn't do that.  It leaves invalid results
 (the remainder is bigger than the divisor!)  Also, what is a good way to
 generate primes in Forth83?  I wrote this as a benchmark, and sort of as
 a way to get my feet wet again.  Any comments would be appreciated.

 Charlie Hitselberger
-----
This message came from GEnie via willett through a semi-automated process.
Report problems to: uunet!willett!dwp or willett!dwp@hobbes.cert.sei.cmu.edu