added multiplication by 10 routine, not yet tested

STATUS.md

@@ -202,7 +202,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$BA2B`   | `mul_FAC2_FAC1`        | PARTIAL  | not testeed yet                                    |
 | `$BA8C`   | `mov_MEM_FAC2`         | DONE     |                                                    |
 | `$BA90`   | `get_FAC2_via_INDEX`   | NOT DONE |                                                    |
-| `$BAE2`   | `mul10_FAC1`           | NOT DONE |                                                    |
+| `$BAE2`   | `mul10_FAC1`           | PARTIAL  | not tested yet                                     |
 | `$BAFE`   | `div10_FAC1_p`         | PARTIAL  | needs `div_FAC2_FAC1`                              |
 | `$BB0F`   | `div_MEM_FAC1`         | PARTIAL  | needs `div_FAC2_FAC1`                              |
 | `$BB12`   | `div_FAC2_FAC1`        | NOT DONE | some work already started                          |

c64/basic/,stubs_math/bae2.mul10_FAC1.s

@@ -1,18 +0,0 @@
-// #LAYOUT# STD *       #TAKE
-// #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
-// #LAYOUT# *   BASIC_0 #TAKE
-// #LAYOUT# *   *       #IGNORE
-
-//
-// Math package - multiply FAC1 by 10
-//
-// See also:
-// - [CM64] Computes Mapping the Commodore 64 - page 114
-// - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
-// - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
-//
-
-// XXX provide implementation
-
-mul10_FAC1:
-	STUB_IMPLEMENTATION()

c64/basic/math/bae2.mul10_FAC1.s

@@ -0,0 +1,43 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+//
+// Math package - multiply FAC1 by 10
+//
+// See also:
+// - [CM64] Computes Mapping the Commodore 64 - page 114
+// - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
+// - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
+//
+
+// XXX test this
+
+mul10_FAC1:
+
+	// Handle special case of FAC1 equal 0
+
+	lda FAC1_exponent
+	beq mul10_FAC1_done
+
+	// Start by multiplying FAC1 by 2
+
+	jsr mul10_FAC1_mul2
+
+	// Move FAC1 to FAC2, so that FAC1 = FAC2 = 2 * initial
+
+	jsr mov_FAC1_FAC2
+
+	// Multiply FAC1 by 4
+
+	jsr mul10_FAC1_mul2
+	jsr mul10_FAC1_mul2
+
+	// Now we have FAC1 = 8 * initial and FAC2 = 2 * initial; so just add these 2 values
+
+	jmp add_FAC2_FAC1
+
+mul10_FAC1_done:
+
+	rts

c64/basic/math/mul10_FAC1_mul2.s

@@ -0,0 +1,25 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+//
+// Multiply FAC1 by 2, do not normalize
+//
+
+mul10_FAC1_mul2:
+
+	// First handle the mantissa
+
+	asl FACOV
+	rol FAC1_mantissa+3
+	rol FAC1_mantissa+2
+	rol FAC1_mantissa+1
+	rol FAC1_mantissa+0
+	bcc !+
+
+	// We need to increment the exponent
+
+	inc FAC1_exponent
+	bcs_16 set_FAC1_max
+
+	rts