PR Stanley wrote:
Hi
isZero :: Int -> Bool
isZero 0 = True
isZero n | n /= 0 = False
The order in which the above equations appear makes no difference to the
application of isZero. Does the Haskell interpreter rewrite patterns
into one single definition using some sort of switch or if construct?
Something a bit like that.
Why does an equation without a guard have to be placed after the more
specific cases?
It doesn't. You could write the above the other way around if you wished.
> To put it another way, why doesn't the interpreter
identify the more specific cases and put them before the general ones.
Because it general it's convenient to have overlapping cases, where the
order matters, and be able to choose the order.
Jules
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