From my point of view (n+k)-patterns have a
very special meaning. This natural numbers
should be considered as a type like this:
data Nat = Zero | Succ Nat
Therefore a (n+k)-pattern is an abbreviation for
Succ(Succ(...Zero...)). It's obvious that
"+" in "(n+k)" doesn't mean a somewhere
else
And now for a little quiz. What's the value of the following (legal)
Haskell expression? (Don't try it with hbc, it fails.)
let (+) + 1 + 1 = (+)
in 1 + 1
Given infixl 6 + (since you can't change this without renaming!):
(+) + 1 + 1
== lpat6 + pat7
And now for a little quiz. What's the value of the following (legal)
Haskell expression? (Don't try it with hbc, it fails.)
let (+) + 1 + 1 = (+)
in 1 + 1
This is illegal syntax!! (+) and (the second) + are the same
variable, thus violating the linearity constraint for
Another strange thing about n+k patterns.
Its definition uses = , but = is not part of the class Num.
Does that mean that n+k patterns have to be instances of class Real?
One could leave it class Num, if the translation were expressed
in terms of "signum" rather than "=".
Question:
Can one
| Another strange thing about n+k patterns.
|
| Its definition uses = , but = is not part of the class Num.
| Does that mean that n+k patterns have to be instances of class Real?
Certainly. In fact, they're really meant to apply only to class
Integral (and it would be natural numbers, if we
