Hi there, thanks for the book - really enjoying it so far!

I have a question on the Chapter 11 Exercise 1 regarding the logical operators.

The label for the bottom checkbox is:

! ( (A && B) || (A||B) )

Which I'm reading as 'NOT when Both are checked OR when A OR B is checked'. Basically not checked if anything else is.

This is what my code's doing, but in the book there's a statement which says "the checkbox is checked at the same time as one of the others - which one and does it make sense"

Well it doesn't make sense to me because my checkbox doesn't follow the behaviour of any of the other checkboxes, also the illustration in the book shows it as checked when A is checked, but I don't see how that's true...

Can anyone shed any light?

Cheers,

Mark

Doesn't matter! I downloaded the code and checked it, and it seems the second condition, the A OR B condition, should be (!A OR !B) thus emulating the Exclusive Or checkbox.

Cheers :)

Mark

Yes, you figured it out!

But there is a typo on that program's form. (Although you'll probably need a magnifying class to read the form at the small size it was printed in the book.)

The last check box's text should be:

!((A && B) || (!A && !B))

If you ignore the outer !, this is "both A and B, or not A and not B." in other words, either both or neither are checked. Add the outer ! back on and you get the Xor function.

Sorry for the confusion. I'll post an update on the book's web site.

__________________
Rod

Rod Stephens, Microsoft MVP

Essential Algorithms: A Practical Approach to Computer Algorithms

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