> Not necessary, everything looks fine! :-)
The statement that "has to compare a whole byte for each possibility, while
the second routine compares 1 bit. That's 8 times more efficient (I think).
" is in error. Comparing a byte against comparing a bit is not 8 times
less efficient. In fact, it really depends how you do things, and what you
want to do. Sometimes comparing a bit is less efficient. Depends which
bit, and if you can modify A, for example. Or if the byte is in memory or a
register.
For example, if I wanted to check to see if bit 4 was set in A, without
destroying A...... how do I do that?
I can't... directly. There's no BIT # instruction. So I have to save the
value somewhere, bit it, and restore it
sta temp ; save A
lda #16 ; the bit we want to check
bit temp ; check the bit
lda temp ; restore
That's ugly. We could shift...
asl
asl
asl
bmi itsset
that's ugly too. Besides, we've destroyed A - against spec - so we'd need
to save/restore it
The point being, it's not always easier to check a bit than to check a byte.
Checking a byte is typically...
cmp #value
beq thesame
> BTW: You can save one more byte (the first ASL) if you use BPL
> instead of BCC.
If up dropped the first ASL, then ALL of the BCC lines should then be
changed to BPL (just clarifying the above).
Cheers
A
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