Previous Posts

Subscribe

Basic feed (just the blog)

The Uberfeed (blog, pics & links)

Via e-mail:

Becky's T-Blog

Monday, February 05, 2007

And then...

2:00PM
I've always wondered: how come AND, OR, and NOT are logical operators, but no BUT?

Is it something to do with my primary school teacher's odd expression "but me no buts!" when you tried to come up with an excuse for something?

Mr Boole, you don't get teachers like that anymore.

2:45
I've said it before and I'll say it again: Milton Keynes is Sim City. I'm certain of it. I've just watched the same car drive past 3 times. It's CG traffic! I swear I just saw the area across the road get re-zoned as "medium commercial". It went all blue and then five identical american gas stations just popped into existence. Honest.

3:00
The funniest thing about Charlie Brooker's rant (referenced in Jane's blog among others) is that the internet version is running alongside two Get a Mac adverts.

I'm in two minds about the Mac adverts, in a way they're exploiting a loophole that lets them relentlessly mock Microsoft by using the generic term "PC". If Microsoft wanted to produce the equivalent pro-Windows advert it wouldn't be able to, because it would be directly attacking Apple. In a way, Charlie's rant is redressing a balance that poor old Microsoft can't.

3:30
Home straight now! I just have the chapter on "Joining Tables" to do and home!

"Joining Tables"... it think this will be about when you need an extra-large table at a big family meal. Maybe there'll be a section on "Finding Extra Chairs".

3:39
I've got to get on. That's yer lot.
Blogger Pandora Caitiff  Hang on. You're talking about logical expressions, then suddenly segue into Boolean expressions...

/gets coat 
Anonymous Sarah F.  Hey that could be the reason why computers are so uncompromising. 
Anonymous Alli' Cat'  Eeeh, joining tables in SQL Server - what's not to love! 
Anonymous Claudia  BUT is logically equivalent to AND:

if A is NOT B BUT C = D

is the same as

if A is NOT B AND C = D

There have been a few languages that have implemented this, or you can macro it in C etc.

OK, so I'm a geek, BUT I look gorgeous in a dress 
Anonymous Stephanie Delacey  I think you're right, Claudia, that BUT is logically equivalent to AND. However, your first line doesn't really represent how "but" is used in normal language.

I would write it as:

if A is NOT B BUT A is C AND B is NOT C

(So, in normal language: Socrates is not a woman - but Socrates is a man. and [implied] a woman is not a man.) 
Blogger Becky  :tries to join in with sage conversation:

Ah, but is it not also said - all Greeks have beards, Aristotle has a beard, therefore Aristotle is a Greek?

:fails: 
Anonymous Stephanie Delacey  I'm afraid so: affirming the consequent - a grave fallacy :) 
Blogger Becky  I dunno why Aristotle didn't just come out as gay.

(Because of the "beard", geddit?) 
Blogger Penny Morris  I'm sure I did an algebra in pure maths once where a = b but b <> a

Or was I asleep in the class and just dreaming it? 
Anonymous Vic  Don't forget 'can't'

As my old teacher said (always) 'There's no such word as can't'

Then trying doing you-know-what while standing up in a hammock. 
Anonymous Isobel  /Winces at the mixing of Boolean and English meaning, so throws in some Japanese for good luck.

The question could always be wrong: Mu. 
Anonymous Stephanie Delacey  Why do you wince, Isobel? One is simply the abstract symbolisation of the other. 
Blogger Valerie S  One is simply the abstract symbolisation of the other ..having lost all the actual meaning on the way.

Sorry Stephanie, but I have religious hatred against logic, originating from the exam I failed because I used symbols a,b,c in my logical deductions instead of the s,v,t that were used in the book (and should always be used in that field of science if you asked the bearded lecturer, who turned dark red and sweaty during the half an hour argument we had about the true , exact meaning of different letters of alphabet).

More seriously, I think artificial intelligence will never emerge before we let go with boolean logic. 
Anonymous Stephanie Delacey  The meaning doesn't matter. It's the form of the argument which gives it it's validity.

Just as 2 + 2 = 4 is true whether you are talking about apples or oranges or bananas. So logical arguments, too, are valid whatever meaning attaches to the terms of the argument.

The only place where meaning is relevant is in examining the truth of the premises of an argument. But once you accept the premises then the argument is valid according to laws of logic alone.

So, Becky's argument about Aristotle is fallacious. No amount of quibbling about meaning will alter that fact. You cannot derive the conclusion that Aristotle is Greek from the two premises given.

For the same reason your lecturer, Valerie, was an idiot - it doesn't matter what symbols you use. It's the form which counts. The letters are mere conventions - all the books I have use p and q, a and b, FGH, and so on because it doesn't actually matter which letters you use so long as it is consistent within one particular argument.

Logic is the queen of science! 
Anonymous Charlee  @ Penny:
perhaps it was
(a -> b) -> (b -> a)

Ie, if a implies b, it doesn't necessarily also hold that b implies a.

what's the opposite of BUT? in English that is? 
Anonymous Stephanie Delacey  The opposite of but in English? Depends how you use the word.

In an adverbial sense the opposite of "but" would be something like "more than". For example, if you said, "It is but a scratch" the opposite would be, "it is more than a scratch" or "it is not only a scratch."

As a preposition the opposite of "but" would be something like "including". For example, "I like all tranny blogs but Becky's". The opposite would be "I like all tranny blogs including Becky's".

As a conjunction the opposite of "but" would be "and also". "She is clever but not very pretty." Opposite: "She is clever and also very pretty." 
Blogger sim  So a piece of rope with a loop and integrated sheet bend = knot

Its logical , but is it bowline ? 
Blogger Penny Morris  I think you might be right Charlee. One of the three properties of a topological space is that you can define a metric on it, and I think your example was a demonstration that there is no metric.

Either that or it was something in Group theory.

Sorry, what were we talking about? 
Anonymous Isobel  What were we talking about?

I really don't know anymore. I gave up after the liquified remains of my brain dribbled out of my left ear and made a nasty stain on the carpet.

The last thing I remember was something about not being able to infer a result in Boolean logic, that the inference was only in the mind of the programmer until it was subjected to a test, when it became a result rather than an inference.
....then something about cats....
....then I noticed I was standing in something sticky... 

Post a CommentPermalink     Subscribe to comments: this post | all posts

<< T*Blog Home