d0evert@dtek.chalmers.se (Mats Olsson) (09/22/90)
Hi there!
It seems to be impossible to use HP48/28`s built-in colecter
and expander to manipulate boolean expression, such like
(A OR B) AND NOT A.
Thats`s because I wonder if someone of YOU have written any
little program to make such manipulations. What I really mean
is a program which makes use of De Morgans Theorem to "solve"
and make such expressions easier.
Example: NOT (A OR B) <=> NOT (A) AND NOT (B)
A AND NOT A = 0
etc, etc
The expressions can, of cause, be much more complicated than theese exaples.
That`s because I Need the program!!
Please let me know how to use the HP for this, if anyone know something
about it (which I bet at least ONE of you out there do!)
Thanks a lot
Mats
pedz@halley.UUCP (09/25/90)
>Example: NOT (A OR B) <=> NOT (A) AND NOT (B) > > A AND NOT A = 0 This looks like a good place to use ^match and Vmatch. I've used this only once of twice but it can definately do what you want. e.g. << { '&a AND NOT &a' '0' } ^MATCH >> Would be the second example. But I don't have much insight as to when to use ^MATCH as oppose to VMATCH. I understand (sorta) how they differ but don't understand when to use one or the other. Anyone care to comment? pedz
bson@rice-chex.ai.mit.edu (Jan Brittenson) (09/25/90)
In article <996@halley.UUCP> pedz@halley.UUCP writes: > I don't have much insight as to when to use ^MATCH as oppose to > VMATCH. I understand (sorta) how they differ but don't understand > when to use one or the other. Assume you want to make the (very reasonable) reduction of '&A+(&B+&C)' to '&A+&B+&C'. With the simple algebraic '1+(2+3)' everything will be just fine, you'll end up with '1+2+3' either way. But try it with '1+(2+(3+4))', and you'll end up with vMATCH ==> '1+2+(3+4)' ^MATCH ==> '1+(2+3+4)' Why is this? Well, ^MATCH looks at the innermost subexpression first (the bottommost, if you regard the expression as a tree), so the matching order will be (with the algebraic '1+(2+(3+4))'): &A+(&B+&C) vs. '3+4' (no match) - "" - vs. '2+(3+4)' -> '2+3+4' - "" - vs. '1+(2+3+4)' (no match) ==> '1+(2+3+4)' vMATCH attempts to substitute the topmost level first, so the order with vMATCH will be: &A+(&B+&C) vs. '1+(2+(3+4))' -> '1+2+(3+4)' - "" - vs. '3+4' (no match) ==> '1+2+(3+4)'