From 5404a40b128aeb89469b03f0814abe08df2c238b Mon Sep 17 00:00:00 2001
From: Rikard Nordgren <hrn@posteo.net>
Date: Mon, 7 Apr 2025 18:54:06 +0200
Subject: [PATCH 1/2] Set flags correctly at return of FCOMP

Flags now directly reflect the results of the comparison
---
 src/basic/math/FCOMP.s | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/src/basic/math/FCOMP.s b/src/basic/math/FCOMP.s
index 1a754efd..9c38d69d 100644
--- a/src/basic/math/FCOMP.s
+++ b/src/basic/math/FCOMP.s
@@ -12,7 +12,7 @@
 ;
 ; Output:
 ; - .A - $00 for equal, $01 for FAC1 > RAM, $FF for FAC1 < RAM
-; - flags N/Z, depending on whether FAC1 is 0, positive, or negative
+; - flags N/Z, Z=1 if equal, N=1 if FAC1 < RAM, Z=0, N=0 if FAC1 > RAM
 ;
 ; Notes:
 ; - uses vector at $24, leaves FAC1 and FAC2 unchanged (Codebase64)
@@ -28,9 +28,6 @@ FCOMP:
     sta INDEX+2
     sty INDEX+3
 
-    jsr sgn_FAC1_A          ; Set N/Z flag for FAC1 and store on stack
-    php
-
     ldy #$01
     lda (INDEX+2),Y
     eor FAC1_sign           ; Check if signs are different
@@ -69,7 +66,6 @@ FCOMP:
 
 FCOMP_equal:
     lda #$00
-    plp
     rts
 
 
@@ -78,7 +74,6 @@ FCOMP_less_than:
     bpl FCOMP_FF
 FCOMP_01:
     lda #$01
-    plp
     rts
     
 FCOMP_greater_than:
@@ -86,5 +81,4 @@ FCOMP_greater_than:
     bpl FCOMP_01
 FCOMP_FF:
     lda #$FF
-    plp
     rts

From db9af4c19ea3ab10a3bb435c95b98b1541797098 Mon Sep 17 00:00:00 2001
From: Rikard Nordgren <hrn@posteo.net>
Date: Mon, 7 Apr 2025 18:58:43 +0200
Subject: [PATCH 2/2] Add sin_FAC1

---
 STATUS.md                                    |  4 +-
 src/basic/,stubs_math/e26b.sin_FAC1.s        | 29 -----------
 src/basic/{,stubs_math => math}/e26b.interop |  0
 src/basic/math/e26b.sin_FAC1.s               | 55 ++++++++++++++++++++
 src/basic/math/poly_sin.s                    | 23 ++++++++
 strings/85248425A0                           |  3 ++
 6 files changed, 83 insertions(+), 31 deletions(-)
 delete mode 100644 src/basic/,stubs_math/e26b.sin_FAC1.s
 rename src/basic/{,stubs_math => math}/e26b.interop (100%)
 create mode 100644 src/basic/math/e26b.sin_FAC1.s
 create mode 100644 src/basic/math/poly_sin.s
 create mode 100644 strings/85248425A0

diff --git a/STATUS.md b/STATUS.md
index 53bab291..408f61ae 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -253,8 +253,8 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$E097`   | `rnd_FAC1`             | DONE     |                                                    |
 | `$E09A`   | `rnd_A`                | DONE     |                                                    |
 | `$E0BE`   | `rnd_generate`         | DONE     |                                                    |
-| `$E264`   | `cos_FAC1`             | PARTIAL  | needs `sin_FAC1`                                   |
-| `$E26B`   | `sin_FAC1`             | NOT DONE | some work already started                          |
+| `$E264`   | `cos_FAC1`             | PARTIAL  | not fully tested yet                               |
+| `$E26B`   | `sin_FAC1`             | PARTIAL  | not fully tested yet                               |
 | `$E2B4`   | `tan_FAC1`             | NOT DONE |                                                    |
 | `$E30E`   | `atn_FAC1`             | NOT DONE |                                                    |
 
diff --git a/src/basic/,stubs_math/e26b.sin_FAC1.s b/src/basic/,stubs_math/e26b.sin_FAC1.s
deleted file mode 100644
index f1f2f340..00000000
--- a/src/basic/,stubs_math/e26b.sin_FAC1.s
+++ /dev/null
@@ -1,29 +0,0 @@
-;; #LAYOUT# STD *       #TAKE
-;; #LAYOUT# *   BASIC_0 #TAKE
-;; #LAYOUT# *   *       #IGNORE
-
-;
-; Math package - sine of FAC1 in radians
-;
-; See also:
-; - [CM64] Computes Mapping the Commodore 64 - page 210 - XXX address does not match
-; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
-; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
-;
-
-; XXX provide implementation
-
-sin_FAC1:
-
-	+STUB_IMPLEMENTATION
-
-poly_sin:
-
-	!byte $05                          ; series length - 1
-
-	+PUT_CONST_POLY_SIN_1
-	+PUT_CONST_POLY_SIN_2
-	+PUT_CONST_POLY_SIN_3
-	+PUT_CONST_POLY_SIN_4
-	+PUT_CONST_POLY_SIN_5
-	+PUT_CONST_POLY_SIN_6
diff --git a/src/basic/,stubs_math/e26b.interop b/src/basic/math/e26b.interop
similarity index 100%
rename from src/basic/,stubs_math/e26b.interop
rename to src/basic/math/e26b.interop
diff --git a/src/basic/math/e26b.sin_FAC1.s b/src/basic/math/e26b.sin_FAC1.s
new file mode 100644
index 00000000..65c48f0f
--- /dev/null
+++ b/src/basic/math/e26b.sin_FAC1.s
@@ -0,0 +1,55 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# *   BASIC_0 #TAKE
+;; #LAYOUT# *   *       #IGNORE
+
+;
+; Math package - sine of FAC1 in radians
+;
+; See also:
+; - [CM64] Computes Mapping the Commodore 64 - page 210 - XXX address does not match
+; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
+; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
+; - https://www.c64-wiki.com/wiki/SIN
+
+
+
+sin_FAC1:
+
+    jsr mov_FAC1_FAC2               ; FAC1 <- X / (2*pi)     (X2)
+    ldy #>const_DOUBLE_PI
+    lda #<const_DOUBLE_PI
+    jsr mov_MEM_FAC1
+    jsr div_FAC2_FAC1
+
+    jsr mov_FAC1_FAC2               ; FAC2 <- X2
+    jsr int_FAC1                    ; FAC1 <- INT(X2)
+    jsr sub_FAC2_FAC1               ; FAC1 <- X2 - INT(X2)   (F)
+
+    ldy #>const_QUARTER
+    lda #<const_QUARTER
+    jsr FCOMP
+    bmi sin_next                    ; FAC1 < 0.25
+
+    ldy #>sin_three_quarters
+    lda #<sin_three_quarters
+    jsr FCOMP
+    bmi sin_q23                     ; FAC1 < 0.75
+
+    jsr mov_FAC1_FAC2               ; FAC1 <- FAC1 - 1.0
+    ldy #>const_ONE
+    lda #<const_ONE
+    jsr mov_MEM_FAC1
+    jsr sub_FAC2_FAC1
+    +bra sin_next
+
+sin_q23:
+    ldy #>const_HALF
+    lda #<const_HALF
+    jsr sub_MEM_FAC1                ; FAC1 <- 0.5 - FAC1
+
+    ; FALLTHROUGH
+    
+sin_next:
+    ldy #>poly_sin
+    lda #<poly_sin
+    jmp poly1_FAC1
diff --git a/src/basic/math/poly_sin.s b/src/basic/math/poly_sin.s
new file mode 100644
index 00000000..1f37c2e6
--- /dev/null
+++ b/src/basic/math/poly_sin.s
@@ -0,0 +1,23 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+;; #LAYOUT# *  BASIC_0  #TAKE
+;; #LAYOUT# *   *       #IGNORE
+
+; Polynomial for the sine function
+
+
+poly_sin:
+
+	!byte $05                          ; series length - 1
+
+	+PUT_CONST_POLY_SIN_1
+	+PUT_CONST_POLY_SIN_2
+	+PUT_CONST_POLY_SIN_3
+	+PUT_CONST_POLY_SIN_4
+	+PUT_CONST_POLY_SIN_5
+	+PUT_CONST_POLY_SIN_6
+
+	
+; Constant 0.75 needed for sine calculation
+sin_three_quarters:
+    !byte $80, $40, $00, $00, $00
diff --git a/strings/85248425A0 b/strings/85248425A0
new file mode 100644
index 00000000..86536202
--- /dev/null
+++ b/strings/85248425A0
@@ -0,0 +1,3 @@
+STA $24 + STY $25 + LDY fragment
+
+Store YA to well known vector address in the zero page