[pforth] / fth / math.fth

\ @(#) math.fth 98/01/26 1.2
\ Extended Math routines
\ FM/MOD SM/REM
\
\ Author: Phil Burk
\ Copyright 1994 3DO, Phil Burk, Larry Polansky, David Rosenboom
\
\ The pForth software code is dedicated to the public domain,
\ and any third party may reproduce, distribute and modify
\ the pForth software code or any derivative works thereof
\ without any compensation or license.  The pForth software
\ code is provided on an "as is" basis without any warranty
\ of any kind, including, without limitation, the implied
\ warranties of merchantability and fitness for a particular
\ purpose and their equivalents under the laws of any jurisdiction.

anew task-math.fth
decimal

: FM/MOD { dl dh nn | dlp dhp nnp rem quo -- rem quo , floored }
   dl dh dabs -> dhp -> dlp
   nn abs -> nnp
   dlp dhp nnp um/mod -> quo -> rem
   dh 0<
   IF  \ negative dividend
       nn 0<
       IF   \ negative divisor
           rem negate -> rem
       ELSE  \ positive divisor
           rem 0=
           IF
               quo negate -> quo
           ELSE
               quo 1+ negate -> quo
               nnp rem - -> rem
           THEN
       THEN
   ELSE  \ positive dividend
       nn 0<
       IF  \ negative divisor
           rem 0=
           IF
               quo negate -> quo
           ELSE
               nnp rem - negate -> rem
               quo 1+ negate -> quo
           THEN
       THEN
   THEN
   rem quo
;

: SM/REM { dl dh nn | dlp dhp nnp rem quo -- rem quo , symmetric }
   dl dh dabs -> dhp -> dlp
   nn abs -> nnp
   dlp dhp nnp um/mod -> quo -> rem
   dh 0<
   IF  \ negative dividend
       rem negate -> rem
       nn 0>
       IF   \ positive divisor
           quo negate -> quo
       THEN
   ELSE  \ positive dividend
       nn 0<
       IF  \ negative divisor
           quo negate -> quo
       THEN
   THEN
   rem quo
;


: /MOD ( a b -- rem quo )
   >r s>d r> sm/rem
;

: MOD ( a b -- rem )
   /mod drop
;

: */MOD ( a b c -- rem a*b/c , use double precision intermediate value )
   >r m*
   r> sm/rem
;
: */ ( a b c -- a*b/c , use double precision intermediate value )
   */mod
   nip
;