Rotate bits

aeklo

I've been trying to figure out a simple method of rotating bits in Stamp Basic, but need some help...
Is there a function or simple way of doing a bit rotationof eg. a byte?

Something like:
B1 VAR Byte
B1 = %00000001
rot(B1) 'gives %10000000
rot(B1) 'gives %01000000
rot(B1) 'gives %00100000
etc.

/Anders

Tracy Allen

Check out the ">>" operator:
B1 VAR Byte
B1 = %00000001
B1 = B1<< 7
B1 = B1 >> 1
B1 = B1 >> 1

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Tracy Allen
www.emesystems.com

Jon Williams

Keep in mind that the shift instructions drop of the "end" bit, depending on which way you're shifting.· You can create a subroutine that allows you to catch that bit and put it back into the other side:

Rotate_Left:
··DO WHILE (idx > 0)
····carry = temp.BIT7
··· temp = temp << 1
··· temp.BIT0·= carry
··· idx = idx - 1
· LOOP
· RETURN

Rotate_Right:
··DO WHILE (idx > 0)
····carry = temp.BIT0
··· temp = temp·>> 1
··· temp.BIT7·= carry
··· idx = idx - 1
· LOOP
· RETURN

In·either case, temp gets rotated, carry is a bit-variable for·storage, and idx is the number of positions to rotate.
·


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Jon Williams
Applications Engineer, Parallax

aeklo

Thanks Jon! That procedure will do

/Anders