Add exp_FAC1

Had to deactivate it for MEGA65 because of conflicting code also placed at e000

STATUS.md

@@ -256,7 +256,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$BF78`   | `pwr_FAC2_MEM`         | DONE     | From the Microsoft BASIC, no label                 |
 | `$BF7B`   | `pwr_FAC2_FAC1`        | NOT DONE |                                                    |
 | `$BFB4`   | `toggle_sign_FAC1`     | DONE     | From the Microsoft BASIC, original name: NEGOP     |
-| `$BFED`   | `exp_FAC1`             | NOT DONE |                                                    |
+| `$BFED`   | `exp_FAC1`             | DONE     | From the Microsoft BASIC, original name: EXP       |
 | `$E043`   | `poly1_FAC1`           | DONE     | From the Microsoft BASIC, original name: POLYX     |
 | `$E059`   | `poly2_FAC1`           | DONE     | From the Microsoft BASIC, original name: POLY      |
 | `$E097`   | `rnd_FAC1`             | DONE     |                                                    |

src/basic/,stubs_math/bfed.exp_FAC1.s

@@ -1,20 +0,0 @@
-;; #LAYOUT# STD *       #TAKE
-;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
-;; #LAYOUT# *   BASIC_0 #TAKE
-;; #LAYOUT# *   *       #IGNORE
-
-;
-; Math package - exponential function, e raised to FAC1 power
-;
-;
-; See also:
-; - [CM64] Computes Mapping the Commodore 64 - page 117
-; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
-; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
-;
-
-; XXX provide implementation
-
-exp_FAC1:
-
-	+STUB_IMPLEMENTATION

src/basic/math_trans/bfed.exp_FAC1.s

@@ -0,0 +1,47 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+;; #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 - exponential function, e raised to FAC1 power
+;
+; This is verified to be almost identical to the original Microsoft implementation where it was named EXP.
+; The addition is the jmp between the two ROMs
+;
+; See also:
+; - [CM64] Computes Mapping the Commodore 64 - page 117
+; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
+; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
+;
+
+; FIRST SAVE THE ORIGINAL ARGUMENT AND MULTIPLY THE FAC BY
+; LOG2(E). THE RESULT IS USED TO DETERMINE IF OVERFLOW
+; WILL OCCUR SINCE EXP(X)=2^(X*LOG2(E)) WHERE
+; LOG2(E)=LOG(E) BASE 2. THEN SAVE THE INTEGER PART OF
+; THIS TO SCALE THE ANSWER AT THE END. SINCE
+; 2^Y=2^INT(Y)*2^(Y-INT(Y)) AND 2^INT(Y) IS EASY TO COMPUTE.
+; NOW COMPUTE 2^(X*LOG2(E)-INT(X*LOG2(E)) BY
+; P(LN(2)*(INT(X*LOG2(E))+1)-X) WHERE P IS AN APPROXIMATION
+; POLYNOMIAL. THE RESULT IS THEN SCALED BY THE POWER OF 2
+; PREVIOUSLY SAVED.
+
+!ifdef CONFIG_TRANSCENDENTAL_FUNCTIONS {
+!ifdef CONFIG_MEMORY_MODEL_38K {
+
+exp_FAC1:
+
+        lda #<const_INV_LOG_2       ; Multiply by log_2(e)
+        ldy #>const_INV_LOG_2
+        jsr mul_MEM_FAC1
+        lda FACOV
+        adc #$50
+        bcc @1
+        jsr INCRND
+@1      jmp STOLD                   ; The BASIC ROM ends here so we need to jump to the KERNAL ROM
+       
+ } else {
+    jmp do_NOT_IMPLEMENTED_error
+} }

src/basic/math_trans/e000.exp_FAC1_contd.s

@@ -0,0 +1,53 @@
+;; #LAYOUT# STD *       #TAKE
+;; #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.
+
+; Continuation of the exp function in the BASIC part of KERNAL ROM
+
+!ifdef CONFIG_TRANSCENDENTAL_FUNCTIONS {
+!ifdef CONFIG_MEMORY_MODEL_38K {
+
+STOLD:
+        sta OLDOV
+        jsr mov_FAC1_FAC2           ; To save in FAC2 without ROUND
+        lda FAC1_exponent
+        cmp #$88                    ; IF abs(FAC1) >= 128, too big
+        bcc @3  
+
+@2
+        jsr MLDVEX                 	; overflow or overflow
+@3
+        jsr int_FAC1
+        lda CHARAC                  ; Get low part
+        clc
+        adc #$81
+        beq @2                      ; overflow or overflow !!
+        sec
+        sbc #1                      ; Subtract 1
+        pha                         ; Save a while
+        ldx #5                      ; Prep to swap FAC1 and FAC2
+@4
+        lda FAC2_exponent,X
+        ldy FAC1_exponent,X
+        sta FAC1_exponent,X
+        sty FAC2_exponent,X
+        dex
+        bpl @4
+        lda OLDOV
+        sta FACOV
+        jsr sub_FAC2_FAC1
+        jsr toggle_sign_FAC1        ; Negate FAC1
+        lda #<poly_exp
+        ldy #>poly_exp
+        jsr poly2_FAC1
+        lda #$00
+        sta ARISGN                  ; Multiply by positive 1.0
+        pla                         ; Get scale factor
+        jsr MLDEXP                  ; Modify FAC1_exponent and check for overflow
+        rts
+        
+ }
+ }

tools/similarity.c

@@ -32,8 +32,8 @@ unsigned short microsoft_basic_chunks[NUM_CHUNKS * 2] = {
     0xB983, 0xBDC1,
     0xBDDD, 0xBF51,
     0xBF71, 0xBF7A,
-    0xBFB4, 0xBFEC,
-    0xE043, 0xE08C,
+    0xBFB4, 0xBFFF,
+    0xE000, 0xE08C,
     0xE264, 0xE2C2,     // Two byte gap here is an optimization
     0xE2C5, 0xE37A,
 };