Add QINT

src/basic/math/bc9b.QINT.s

@@ -0,0 +1,51 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+;; #LAYOUT# *   BASIC_0 #TAKE
+;; #LAYOUT# *   *       #IGNORE
+
+;
+; Math package - Quick conversion of FAC1 to 32 bit signed integer
+;
+; Output:
+; - $62-$65, big-endian order
+;
+; See also:
+; - [CM64] Computes Mapping the Commodore 64 - page 115
+; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
+;
+
+
+QINT:
+ 	;QUICK GREATEST INTEGER FUNCTION.
+	;LEAVES INT(FAC) IN FACHO&MO&LO SIGNED.
+	;ASSUMES FAC .LT. 2^23 = 8388608
+
+	lda FAC1_exponent
+	beq clear_FAC1          ; If zero, got it.
+	sec
+	sbc #$A0                ; Get number of places to shift.
+	bit FAC1_sign
+	bpl @1
+	tax
+	lda #$FF
+	sta BITS
+	jsr neg_FAC1_mantissa
+	txa
+@1: ldx #FAC1_exponent
+    cmp #$F9
+    bpl QINT1                   ; If number of places >= 7 shift 1 place at a time.
+    jsr shiftr_FAC
+    sty BITS                    ; Zero bits since adder wants zero.
+QINT_ret:
+    rts
+
+QINT1:
+    tay                             ; Put count in counter
+    lda FAC1_sign
+    and #$80                        ; Get sign bit
+    lsr FAC1_mantissa               ; Save first shifted byte
+    ora FAC1_mantissa
+    sta FAC1_mantissa
+    jsr short_shift_FAC             ; Shift the rest
+    sty BITS                        ; Zero [BITS]
+    rts

src/basic/math/bc9b.interop

@@ -0,0 +1,4 @@
+This is an important floating point math routine, documented in many places.
+
+Example code utilizing this routine:
+- https://github.com/irmen/prog8/blob/master/compiler/res/prog8lib/c64flt.p8