Just to amuse you all, here's a quick Haskell 98 quiz:
What do the following definitions do:
1 x + 1 = f x
2 (x + 1) = f 2
3 (x + 1) * 2 = f x
4 (x + 1) 2 = g x
That's right!
(1) partially defines (+). One could add more equations, thus:
x + 1 = f x
x + other = g x
(2) is a pattern binding that binds x. It's quite like
Just x = f 2
except that the pattern is an n+k pattern
(3) is a function binding rather like (1), except that it defines (*).
The (*) operator has two operands: an n+k pattern (x+1) and 2.
(4) is a new possibility in Haskell 98.
It defines (+), albeit differently to (1). Here the (+) has
three operands, namely x, 1, and 2, so it will have a different
type to the usual (+) but never mind.
I don't propose to change this, because in practice it doesn't seem
to cause much of a problem, but it seems pretty confusing. To my mind
the culprit is clear: n+k patterns. But they are staying in Haskell 98.
Simon
