;; #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 - subtract FAC1 from FAC2
;
; This is verified to be identical to the original Microsoft implementation where it was named FSUBT.
;
; See also:
; - [CM64] Computes Mapping the Commodore 64 - page 112
; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
;


sub_FAC2_FAC1:

    ; Toggle FAC1 sign
    lda FAC1_sign
    eor #$FF
    sta FAC1_sign
    eor FAC2_sign
    sta ARISGN
    lda FAC1_exponent       ; Set flags from exponent

	; Perform addition
    jmp add_FAC2_FAC1
