From 5127e416437586ea9ec030db73e9cc5859595b85 Mon Sep 17 00:00:00 2001
From: Rikard Nordgren <hrn@posteo.net>
Date: Tue, 14 Apr 2026 21:00:25 +0200
Subject: [PATCH] Update poly2_FAC1

---
 STATUS.md                              |  2 +-
 src/basic/math_trans/e059.poly2_FAC1.s | 80 ++++++++++++--------------
 tools/similarity.c                     |  2 +-
 3 files changed, 40 insertions(+), 44 deletions(-)

diff --git a/STATUS.md b/STATUS.md
index 22f7a032..08650c8b 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -258,7 +258,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$BFB4`   | `toggle_sign_FAC1`     | DONE     | From the Microsoft BASIC, original name: NEGOP     |
 | `$BFED`   | `exp_FAC1`             | NOT DONE |                                                    |
 | `$E043`   | `poly1_FAC1`           | DONE     | From the Microsoft BASIC, original name: POLYX     |
-| `$E059`   | `poly2_FAC1`           | PARTIAL  | not fully tested yet                               |
+| `$E059`   | `poly2_FAC1`           | DONE     | From the Microsoft BASIC, original name: POLY      |
 | `$E097`   | `rnd_FAC1`             | DONE     |                                                    |
 | `$E09A`   | `rnd_A`                | DONE     |                                                    |
 | `$E0BE`   | `rnd_generate`         | DONE     |                                                    |
diff --git a/src/basic/math_trans/e059.poly2_FAC1.s b/src/basic/math_trans/e059.poly2_FAC1.s
index 64617c7b..3755ee5f 100644
--- a/src/basic/math_trans/e059.poly2_FAC1.s
+++ b/src/basic/math_trans/e059.poly2_FAC1.s
@@ -2,9 +2,13 @@
 ;; #LAYOUT# *   BASIC_0 #TAKE
 ;; #LAYOUT# *   *       #IGNORE
 
-;
+; This file is under the MIT license, it contains code released by Microsoft Corporation.
+; See LICENSE for more information.
+
 ; Math package - evaluate polynomial with odd and even powers for FAC1 value
 ;
+; This is verified to be identical to the original Microsoft implementation where it was named POLY.
+;
 ; Input:
 ; - .A - table address low byte
 ; - .Y - table address low byte
@@ -28,48 +32,40 @@
 
 
 poly2_FAC1:
-    jsr store_YA_in_ZP
+        sta POLYPT
+        sty POLYPT+1
+        
+POLY1:
+        jsr mov_r_FAC1_TMP2     ; Save FAC1
+        lda (POLYPT),Y
+        sta DEGREE
+        ldy POLYPT
+        iny
+        tya
+        bne POLY3
+        inc POLYPT+1
+POLY3:
+        sta POLYPT
+        ldy POLYPT+1
+POLY2:
+        jsr mul_MEM_FAC1
+        lda POLYPT             ; Get current pointer
+        ldy POLYPT+1
+        clc
+        adc #5
+        bcc POLY4
+        iny
+POLY4:
+        sta POLYPT
+        sty POLYPT+1
+        jsr add_MEM_FAC1        ; Add in constant
+        lda #<TEMPF2            ; Multiply the original FAC1
+        ldy #>TEMPF2
+        dec DEGREE              ; Done?
+        bne POLY2
+RANDRT:
+        rts                     ; Yes
 
-poly2_table_in_index2:  ; Called from poly1
-    ldy #$00            ; FAC1 -> TMPF2
-    ldx #TEMPF2
-    jsr mov_FAC1_MEM
-
-    ldx #$80            ; 0 -> FAC1
-    stx FAC1_exponent
-
-    ldx #0
-    lda (INDEX+2, x)    ; degree (degree+1 = num coeffs)
-    sta SGNFLG          ; number of terms register
-    inc INDEX+2
-    bcc @1
-    inc INDEX+3
-
-@1:
-    lda INDEX+2
-    ldy INDEX+3
-    jsr add_MEM_FAC1    ; Add with coefficient
-    ldy #$00
-    lda #TEMPF2
-    jsr mul_MEM_FAC1    ; Multiply with x
-
-    clc                 ; Add 5 to table pointer
-    lda #$05
-    adc INDEX+2
-    sta INDEX+2
-    bcc @2
-    inc INDEX+3
-
-@2:
-    dec SGNFLG
-    bpl @1
-    rts
-
-
-store_YA_in_ZP:     ; Used also by poly1
-    sty INDEX+3     ; Store YA in second INDEX pointer
-    sta INDEX+2
-    rts
 
 
 } else {
diff --git a/tools/similarity.c b/tools/similarity.c
index 81f586c5..77821498 100644
--- a/tools/similarity.c
+++ b/tools/similarity.c
@@ -32,7 +32,7 @@ unsigned short microsoft_basic_chunks[NUM_CHUNKS * 2] = {
     0xBDB3, 0xBDC1,
     0xBDDD, 0xBF51,
     0xBFB4, 0xBFEC,
-    0xE043, 0xE058,
+    0xE043, 0xE08C,
     0xE264, 0xE2C2,     // Two byte gap here is an optimization
     0xE2C5, 0xE37A,
 };