>> Heh. If you mean "why isn't it some random symbol?" then the answer is 
>> "you can only use symbols for *binary* functions, not *unary* functions 
>> such as NOT".
> 
>   How do you negate an integral or floating point value, then?

Haskell possesses exactly *one* unary operator: unary minus. (Because, 
let's face it, not having this would just be annoying.) This is 
hard-wired into the language spec, however. You cannot define new unary 
operators.

The existence of the unary minus operator causes the following glitch:

   (5+) is a function.
   (5-) is a function.
   (5*) is a function.
   (5/) is a function.
   (+5) is a function.
   (-5) is a number.
   (*5) is a function.
   (/5) is a function.

Spot the odd one out. (There's a library function named "subtract" so 
that you can write "subtract 5" instead of "(-5)" to get a function.)

And it *is* unary minus, not part of the numeric literal syntax; for 
example "-x" works just as well as "-5" does.

(Saying "-x" is equivilent to saying "negate x". In particular, since 
unary minus is a syntax quirk, you can't define it directly. You define 
"negate" directly, and the compiler does the rest. Also, just for 
giggles, the default implementation of binary minus is "x - y = x + 
(negate y)"...)

So there - aren't you sorry you asked?

You may also have noticed that "sin -5" doesn't work. That's because 
it's interpretted as *binary* minus, i.e. "sin - 5", which obviously 
doesn't type-check. And *that* is why you have to say "sin (-5)". 
Annoying, isn't it?

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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