From 488f5b150333d89aff0d63f423e101f3eb3939a8 Mon Sep 17 00:00:00 2001
From: Rikard Nordgren <hrn@posteo.net>
Date: Wed, 9 Apr 2025 22:03:09 +0200
Subject: [PATCH] Add log_FAC1

---
 STATUS.md                                     |  2 +-
 src/,,config_ultimate64.s                     |  4 +-
 src/basic/,stubs_math/b9ea.log_FAC1.s         | 30 ---------
 src/basic/{,stubs_math => math}/b9ea.interop  |  0
 src/basic/math/b9ea.log_FAC1.s                | 64 +++++++++++++++++++
 src/basic/math/poly_log.s                     | 15 +++++
 ...20803504F334813504F334808000000080317217F8 |  1 +
 strings/A9E5A0B9                              |  3 +
 strings/B9200FBBA9                            |  3 +
 strings/B92067B8                              |  3 +
 strings/E0A0E220                              |  3 +
 11 files changed, 95 insertions(+), 33 deletions(-)
 delete mode 100644 src/basic/,stubs_math/b9ea.log_FAC1.s
 rename src/basic/{,stubs_math => math}/b9ea.interop (100%)
 create mode 100644 src/basic/math/b9ea.log_FAC1.s
 create mode 100644 src/basic/math/poly_log.s
 create mode 100644 strings/18608100000000037F5E56CB7980139B0B6480763893168238AA3B20803504F334813504F334808000000080317217F8
 create mode 100644 strings/A9E5A0B9
 create mode 100644 strings/B9200FBBA9
 create mode 100644 strings/B92067B8
 create mode 100644 strings/E0A0E220

diff --git a/STATUS.md b/STATUS.md
index eefbbbb9..0f402fd3 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -212,7 +212,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$B86A`   | `add_FAC2_FAC1`        | DONE     |                                                    |
 | `$B8FE`   | `normal_FAC1`          | DONE     |                                                    |
 | `$B947`   | `inv_FAC1_mantissa`    | DONE     |                                                    |
-| `$B9EA`   | `log_FAC1`             | NOT DONE |                                                    |
+| `$B9EA`   | `log_FAC1`             | PARTIAL  | not fully tested yet                               |
 | `$BA28`   | `mul_MEM_FAC1`         | DONE     |                                                    |
 | `$BA2B`   | `mul_FAC2_FAC1`        | DONE     |                                                    |
 | `$BA8C`   | `mov_MEM_FAC2`         | DONE     |                                                    |
diff --git a/src/,,config_ultimate64.s b/src/,,config_ultimate64.s
index 109788c1..e292e4b0 100644
--- a/src/,,config_ultimate64.s
+++ b/src/,,config_ultimate64.s
@@ -96,8 +96,8 @@
 ; --- Eye candy
 
 ;; #CONFIG# COLORS_BRAND               YES
-;; #CONFIG# BANNER_SIMPLE              NO
-;; #CONFIG# BANNER_FANCY               YES
+;; #CONFIG# BANNER_SIMPLE              YES
+;; #CONFIG# BANNER_FANCY               NO
 ;; #CONFIG# SHOW_FEATURES              YES
 
 
diff --git a/src/basic/,stubs_math/b9ea.log_FAC1.s b/src/basic/,stubs_math/b9ea.log_FAC1.s
deleted file mode 100644
index b2c293d4..00000000
--- a/src/basic/,stubs_math/b9ea.log_FAC1.s
+++ /dev/null
@@ -1,30 +0,0 @@
-;; #LAYOUT# STD *       #TAKE
-;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
-;; #LAYOUT# *   BASIC_0 #TAKE
-;; #LAYOUT# *   *       #IGNORE
-
-;
-; Math package - natural logarigthm
-;
-;
-; See also:
-; - [CM64] Computes Mapping the Commodore 64 - page 113
-; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
-; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
-;
-
-; XXX provide implementation
-
-log_FAC1:
-
-	+STUB_IMPLEMENTATION
-
-
-poly_log:
-
-    !byte $03                          ; series length - 1
-
-    +PUT_CONST_POLY_LOG_1
-    +PUT_CONST_POLY_LOG_2
-    +PUT_CONST_POLY_LOG_3
-    +PUT_CONST_POLY_LOG_4
diff --git a/src/basic/,stubs_math/b9ea.interop b/src/basic/math/b9ea.interop
similarity index 100%
rename from src/basic/,stubs_math/b9ea.interop
rename to src/basic/math/b9ea.interop
diff --git a/src/basic/math/b9ea.log_FAC1.s b/src/basic/math/b9ea.log_FAC1.s
new file mode 100644
index 00000000..9f2f609d
--- /dev/null
+++ b/src/basic/math/b9ea.log_FAC1.s
@@ -0,0 +1,64 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+;; #LAYOUT# *   BASIC_0 #TAKE
+;; #LAYOUT# *   *       #IGNORE
+
+;
+; Math package - natural logarigthm of FAC1
+;
+;
+; See also:
+; - [CM64] Computes Mapping the Commodore 64 - page 113
+; - 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/LOG
+;
+; Calculate log of FAC1
+; Algorithm:
+; 1. Separate exponent and significand of FAC1.  N = exponent, XF = significand
+; 2. T = 1.0 - sqrt(2.0) / (XF + sqrt(0.5))
+; 3. Apply polynomial 0.43425594189 * T7 + 0.57658454124 * T5 + 0.96180075919 * T3 + 2.8853900731 * T - 0.5  giving log2(XF)
+; 4. N + log2(XF) giving log2(X)
+; 5. Multiply by LOG(2) giving LOG(X)
+
+
+
+log_FAC1:
+    lda FAC1_exponent           ; Store exponent for later
+    pha
+
+    ldx #$80                    ; Set exponent to 0 so that FAC1 becomes XF
+    stx FAC1_exponent
+
+    ldy #>const_INV_SQR_2       ; FAC1 <- FAC1 + sqrt(0.5)
+    lda #<const_INV_SQR_2
+    jsr add_MEM_FAC1
+
+    ldy #>const_SQR_2           ; FAC1 <- sqrt(2.0) / FAC1
+    lda #<const_SQR_2
+    jsr div_MEM_FAC1
+
+    ldy #>const_ONE             ; FAC1 <- 1.0 - FAC1
+    lda #<const_ONE
+    jsr sub_MEM_FAC1
+
+    ldy #>poly_log              ; FAC1 <- log_poly(FAC1)
+    lda #<poly_log
+    jsr poly1_FAC1
+    
+    ldy #>const_NEG_HALF        ; FAC1 <- FAC1 - 0.5
+    lda #<const_NEG_HALF
+    jsr add_MEM_FAC1
+    
+    jsr mov_FAC1_FAC2           ; FAC2 <- FAC1
+
+    pla                         ; FAC1 <- N
+    sec
+    sbc #$80
+    jsr convert_A_to_FAC1
+
+    jsr add_FAC2_FAC1           ; FAC1 <- FAC1 + FAC2
+
+    ldy #>const_LOG_2           ; FAC1 <- FAC1 * log(2.0)
+    lda #<const_LOG_2
+    jmp mul_MEM_FAC1
diff --git a/src/basic/math/poly_log.s b/src/basic/math/poly_log.s
new file mode 100644
index 00000000..494ab76a
--- /dev/null
+++ b/src/basic/math/poly_log.s
@@ -0,0 +1,15 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+;; #LAYOUT# *  BASIC_0  #TAKE
+;; #LAYOUT# *   *       #IGNORE
+
+; Polynomial for the logarithm function
+
+poly_log:
+
+    !byte $03                          ; series length - 1
+
+    +PUT_CONST_POLY_LOG_1
+    +PUT_CONST_POLY_LOG_2
+    +PUT_CONST_POLY_LOG_3
+    +PUT_CONST_POLY_LOG_4
diff --git a/strings/18608100000000037F5E56CB7980139B0B6480763893168238AA3B20803504F334813504F334808000000080317217F8 b/strings/18608100000000037F5E56CB7980139B0B6480763893168238AA3B20803504F334813504F334808000000080317217F8
new file mode 100644
index 00000000..a1d2a6db
--- /dev/null
+++ b/strings/18608100000000037F5E56CB7980139B0B6480763893168238AA3B20803504F334813504F334808000000080317217F8
@@ -0,0 +1 @@
+The polynomial for log and parts of the polynomial for exp. Known polynomials taken from the book "Computer Approximations" by John Fraser Hart et al. (ISBN 0-88275-642-7) according to https://www.c64-wiki.com/wiki/POLY1
diff --git a/strings/A9E5A0B9 b/strings/A9E5A0B9
new file mode 100644
index 00000000..18d9baaa
--- /dev/null
+++ b/strings/A9E5A0B9
@@ -0,0 +1,3 @@
+LDA #$E5 + LDY #$B9
+
+Load address of known floating point constant into YA
diff --git a/strings/B9200FBBA9 b/strings/B9200FBBA9
new file mode 100644
index 00000000..c7892b0e
--- /dev/null
+++ b/strings/B9200FBBA9
@@ -0,0 +1,3 @@
+$B9 + JSR $BB0F + LDA fragment
+
+Fragments + call to known floating point function
diff --git a/strings/B92067B8 b/strings/B92067B8
new file mode 100644
index 00000000..51397276
--- /dev/null
+++ b/strings/B92067B8
@@ -0,0 +1,3 @@
+$B9 + JSR $B867
+
+Fragment + call to known floating point function
diff --git a/strings/E0A0E220 b/strings/E0A0E220
new file mode 100644
index 00000000..3ae3f585
--- /dev/null
+++ b/strings/E0A0E220
@@ -0,0 +1,3 @@
+$E0 + LDY #$E2 + JSR fragment
+
+Code fragment of loading address into AY and calling some function