From a870fc533a845182abbf73d7c28cb30fbdb33019 Mon Sep 17 00:00:00 2001
From: d6 <d_m@plastic-idolatry.com>
Date: Sun, 6 Nov 2022 22:01:45 -0500
Subject: [PATCH] clean up fix16

---
 fix16.tal | 53 ++++++-------------------------------------------
 fixed.tal | 59 -------------------------------------------------------
 2 files changed, 6 insertions(+), 106 deletions(-)
 delete mode 100644 fixed.tal

diff --git a/fix16.tal b/fix16.tal
index 700d143..9c62849 100644
--- a/fix16.tal
+++ b/fix16.tal
@@ -48,14 +48,12 @@
 ( MUL2.                                                   )
 (                                                         )
 ( similarly with division we have:                        )
-( )
-( x divided by #0100 -> x )
-( x divided by #0001 -> x * 256, with likely overfow )
-( #abcd divided by #1000 -> #0abc, rounding with d )
-( x divided by #0200 -> x >> 1 )
-( x divided by #0080 -> x << 1 )
-
-%xyz { ;x16-emit JSR2 #0a #18 DEO }
+(                                                         )
+(     x = x'/256                                          )
+(     y = y'/256                                          )
+(   x/y = z = z'/256                                      )
+(   (x'/256)/(y'/256) = (x'*256 / y)/256                  )
+(    z' = (x' * 256 / y)/256                              )
 
 ( useful constants                       )
 (                                        )
@@ -92,42 +90,6 @@
 
 %x16-emit-dec { #30 ADD #18 DEO }
 
-( |0100
-    x16-zero xyz
-    x16-one xyz
-    x16-two xyz
-    x16-ten xyz
-    x16-hundred xyz
-    x16-pi/2 xyz
-    x16-pi xyz
-    x16-pi*2 xyz
-    x16-e xyz
-    x16-phi xyz
-    x16-sqrt-2 xyz
-    x16-sqrt-3 xyz
-    x16-epsilon xyz
-    #0002 xyz
-    #1234 xyz
-    #7fff xyz
-    #8000 xyz
-    #8001 xyz
-    #ffff xyz
-    #0200 xyz
-    #0834 #0000 ;x16-add JSR2 xyz
-    #0834 #0834 ;x16-add JSR2 xyz
-    #0834 #0834 ;x16-mul JSR2 xyz
-    #0834 #0200 ;x16-div JSR2 xyz
-    #0100 xyz
-    #0003 xyz
-    #0100 #0003 ;x16-div JSR2 xyz
-    #0834 xyz
-    #0080 xyz
-    #0834 #0080 ;x16-div JSR2 xyz
-    #0834 xyz
-    #0300 xyz
-    #0834 #0300 ;x16-div JSR2 xyz
-    BRK )
-
 @x16-emit ( x* -> )
     DUP2 #8000 EQU2 ,&is-min JCN
     DUP2 #8000 GTH2 ,&is-neg JCN
@@ -201,9 +163,6 @@
     &rhs-whole #08 SFT2 MUL2 JMP2r
 
 @x16-div ( x* y* -> x/y* )
-(    DUP ,&not-whole JCN
-        #08 SFT2 DIV2 JMP2r ( since y is whole, x/(y>>8) is correct )
-    &not-whole )
     DIV2k STH2k       ( x y x/y  {x/y}         )
     LITr 80 SFT2r     ( x y x/y  {div=(x/y)<<8 )
     OVR2 STH2         ( x y x/y  {y div}       )
diff --git a/fixed.tal b/fixed.tal
deleted file mode 100644
index 21eb1ec..0000000
--- a/fixed.tal
+++ /dev/null
@@ -1,59 +0,0 @@
-( use short as a fixed point number 8.8 )
-( )
-( so #0001 is interpreted as 1/256 )
-( and #ffff is interpreted as 255+255/256 )
-( )
-( x = x0 + x1/256 )
-( y = y0 + y1/256 )
-( )
-( many 8.8 operations are equivalent to u16: )
-(   * comparisons/equality )
-(   * addition/subtraction )
-( )
-( but due to 16-bit truncation multiplication is different. )
-( )
-( x*y = x0*y0 + x0*y1/256 + x1*y0/256 + x1*y1/65536 )
-( )
-( since we only have 16-bits: )
-(   1. we need to drop the 8 high bits from x0*y0 )
-(   2. we need to drop the 8 low bits from x1*y1 )
-(   3. we need to use all the bits from x0*y1 and x1*y0 )
-
-%EMIT { #18 DEO }
-%DIGIT { #00 SWP ;digits ADD2 LDA EMIT }
-%SPACE { #20 EMIT }
-%NEWLINE { #0a EMIT }
-%EMIT-BYTE { DUP #04 SFT DIGIT #0f AND DIGIT }
-
-( program )
-|0100
-    #0100 #0100 ;mul-fix JSR2 ;emit-short JSR2 NEWLINE
-    #0999 #0100 ;mul-fix JSR2 ;emit-short JSR2 NEWLINE
-    #abcd #0100 ;mul-fix JSR2 ;emit-short JSR2 NEWLINE
-    #0200 #0200 ;mul-fix JSR2 ;emit-short JSR2 NEWLINE
-    #0400 #0200 ;mul-fix JSR2 ;emit-short JSR2 NEWLINE
-    BRK
-
-%LO { NIP #00 SWP }
-%HI { POP #00 SWP }
-
-@mul-fix ( x* y* -> z* )
-    OVR2 OVR2 LO SWP2 LO MUL2 ( x1*y1 )
-        #08 SFT2 STH2 ( z = (x1*y1)>>8 )
-
-    OVR2 OVR2 HI SWP2 LO MUL2 ( x0*y1 )
-        STH2 ADD2r ( z += x0*y1 )
-
-    OVR2 OVR2 LO SWP2 HI MUL2 ( x1*y0 )
-        STH2 ADD2r ( z += x1*y0 )
-
-              HI SWP2 HI MUL2 ( x0*y0 )
-        #80 SFT2 STH2r ADD2 ( z += (x0*y0)<<8 )
-    JMP2r
-
-@emit-short SWP EMIT-BYTE EMIT-BYTE JMP2r
-
-( convenience for less branching when printing hex )
-@digits
-    30 31 32 33 34 35 36 37
-    38 39 61 62 63 64 65 66