[Tutor] Re: How different is math logic from computer logic?

[alan.gauld@bt.com]

> Just out of curiosity, did Boole come up with "nand" or did that come
> later?

It came later but I don't know from where or when exactly.
ISTR Boole didn't even use 'and', 'or' and 'not' he used other 
more mathematically based names. Certainly he didn't use the 
+ and * symbols that Magnus posted, he used the pure math 
notation found in formal notations like VDM and Z.

OR = v
AND = ^

Which are somewhat like the set notations for intersection 
and union. Negation uses a strange symbol somewhat like:  -|
(think about the top corner of a rectangle) and used as 
a superscript in front of the thing being negated.
(The symbol is on the key to the left of the digit 1 on my 
keypad if that helps...)

> For those unfamiliar with it, the nand operator is functionally
> complete.  

As is its twin nor.

> With just nand you can write any logic expression.  The
> combination of and, or and not is also functionally complete.  (it's
> more natural too, but require 3 operators instead of 1)

This is really only of much significance if you are using 
hardware gates to build a solution though! :-)

> If you're really interested in logic or rule based programming, check
> out Prolog.  (I've only heard about it but never used it)

I have played with Micro Prolog and another variant on our old VAX.
Never built anything that other people used, but its a fun language.

Alan g.