in reply to Re^3: A "but" operator. in thread A "but" operator.
I think you are trying to say a "but" operator is equivalent "not and" operator and that !(A>B) is equivalent to "but".
I am assuming that "!" symbolizes the negation operator and ">" symbolized the ifthen ( or implies ) operator.
Yet ...
P  Q  P and Q  !(P and Q) 
T  T  T  F 
T  F  F  T 
F  T  F  T 
F  F  F  T 
So I would say "A and !B"is not equivalent to "!(A > B)" and I wouldn't say "A but B" <=> "A and !B", but I could just be misunderstanding your notation. :)
As far a what a but operator is I would say it should be equivalent to the "Boolean And" operator.
And is not needed in a programming language. The word "but" is used in commonly to emphasis
that an assumption is false. Example ...
If a student where to errorously assume that multiplaction is
the same as addition the student might state ...
1 + 1 = 2 and 2 + 2 = 4 and 2 * 2 = 4 and 1 * 1 = 2
... which we know to be false. The student's teacher would say ...
1 + 1 = 2 and 2 + 2 = 4 and 2 * 2 = 4 but 1 * 1 != 2
... to correct the student.
This is the same as
1 + 1 = 2 and 2 + 2 = 4 and 2 * 2 = 4 and 1 * 1 != 2
T and T and T and T is TRUE
It is not equal to
1 + 1 = 2 and 2 + 2 = 4 and 2 * 2 = 4 and not (1 * 1 != 2)
T and T and T and F is FALSE
But merely gives emphasis to the fact that the student's assumption is false.
Janitored by davido: removed excess spaces within pre tags that caused horizontal scrolling.
Plankton: 1% Evil, 99% Hot Gas. 
Re^5: A "but" operator. by dragonchild (Archbishop) on Sep 27, 2004 at 22:22 UTC 
You forgot a couple ...
P and not Q  !(P > Q) 
F  F 
T  T 
F  F 
F  F 
Hence, the relation holds.
Being right, does not endow the right to be rude; politeness costs nothing. Being unknowing, is not the same as being stupid. Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence. Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.
I shouldn't have to say this, but any code, unless otherwise stated, is untested
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Ahh! I see. I don't know why I was thinking you meant nand !(P and Q). I misunderstood your notation I guess.
The student's teacher would say ...
1 + 1 = 2 and 2 + 2 = 4 and 2 * 2 = 4 but 1 * 1 != 2
... which could be written as ...
1 + 1 = 2 and 2 + 2 = 4 and 2 * 2 = 4 and not (1 * 1 = 2)
I get it now.
Plankton: 1% Evil, 99% Hot Gas. 
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