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+;********************************************************************************
+; @module math
+; @type utility
+; @details
+;   Math library
+;********************************************************************************
+.ifndef INCLUDE_MATH
+INCLUDE_MATH = 1
+
+.scope math
+
+;********************************************************************************
+; @macro Divide a num (or A) by a factor
+; @param num: Memory or A
+; @param divider: must be power of 2
+;********************************************************************************
+.macro div num,divider
+.if divider = 2
+    lsr num
+.elseif divider = 4
+    lsr num
+    lsr num
+.elseif divider = 8
+    lsr num
+    lsr num
+    lsr num
+.elseif divider = 16
+    .repeat 4
+    lsr num
+    .endrepeat
+.elseif divider = 32
+    .repeat 5
+    lsr num
+    .endrepeat
+.elseif divider = 64
+    .repeat 6
+    lsr num
+    .endrepeat
+.elseif divider = 128
+    .repeat 7
+    lsr num
+    .endrepeat
+.else
+    .error "div macro: divider % 2 != 0"
+.endif
+.endmacro
+
+; .macro Amult1 factor
+;     phx
+;     ldx factor
+;     AmultX
+;     plx
+; .endmacro
+
+; https://www.llx.com/Neil/a2/mult.html
+; .macro mult num1,num2,result
+;     lda #0
+;     ldx #8
+; L1: 
+;     lsr num2
+;     bcc L2
+;     clc
+;     adc num1
+; L2:
+;     ror
+;     ror result
+;     dex
+;     bne L1
+;     sta result+1
+; .endmacro
+
+;         00110101
+;         10010011
+;         -------^
+;        =00110101
+;        00110101
+;        01001001
+;        -------^
+;       =00110101
+;       00110101
+;       00100100
+;       -------^
+;      =00000000
+;      00110101
+;      00010010
+;      -------^
+;     =00000000
+;     00110101
+;     00001001
+;     -------^
+;     00110101
+;    00110101
+;    00000100
+;    -------^
+;   =00000000
+;   00110101
+;   00000010
+;   -------^
+;  =00000000
+;  00110101
+;  00000001
+; 00110101
+
+      
+.endscope
+.endif  ; guard