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49 lines
693 B
ArmAsm
49 lines
693 B
ArmAsm
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; Fixed point cosine function.
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;
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; Returns the cosine for the given argument as angular degree.
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; Valid argument range is 0..360
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;
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;
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; Ullrich von Bassewitz, 2009-10-29
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;
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.export _cc65_cos
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.import _cc65_sin
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; ---------------------------------------------------------------------------
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;
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.code
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.proc _cc65_cos
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; cos(x) = sin(x+90)
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clc
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adc #90
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bcc L1
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inx
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; If x is now larger than 360, we need to subtract 360.
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L1: cpx #>360
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bne L2
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cmp #<360
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L2: bcc L4
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sbc #<360
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bcs L3
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dex
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L3: dex
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L4: jmp _cc65_sin
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.endproc
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