Re: "Back & Forth" is back!

In article <nnd$0729bd17$4f184982@a8d623d456fa3140>,
Hans Bezemer  <the.beez.speaks@gmail.com> wrote:

This time, we delve into a forgotten way to handle fixed point
arithmetic. Which IMHO deserves to be dusted off now we entered the
64-bit era!
>
https://www.youtube.com/watch?v=VwPForQL10Y

A one screen fixed point:
----------------------
( *s /s fix-scale  -fixedpoint- )               \ AvdH C3nov06
WANT ALIAS
8 CELLS 4 - CONSTANT fix-scale      \ n represents n.2^-scale.
1 fix-scale    LSHIFT  CONSTANT 1/1
1 fix-scale 1- LSHIFT  CONSTANT 1/2
\ As */ * / but scaled.
: */s    >R UM* R> UM/MOD NIP ;
: *s   1/1 */s ;         : /s   1/1 SWAP */s ;
\ Most other operators remain the same:
'+ ALIAS +s     '- ALIAS -s     '*/ ALIAS */s
\ For a RATIO (n/d) return an equivalent scaled NUMBER.
'/s ALIAS rat>s        \ By accident.
\ Print a scaled double number
: .mantissa 0 DO BASE @  1/1 */MOD &0 + EMIT LOOP DROP SPACE ;
: _D.s    1/1 UM/MOD 0 <# #S #> TYPE &. EMIT 20 .mantissa ;
: U.s 0 _D.s ;
--------------------

For ISO replace   '+  by ' +  or ['] + .
(I can't remember which is which.)

ALIAS gives a new name for an old thing.
In a pinch do
: */s */ ;

WANT signifies that you want ALIAS if it isn't loaded already.

>
Hans Bezemer

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