Stefan O'Rear wrote:
Unfortunately, ignoring purity is fraught with peril. One notable
example recently is in HAppS, a Haskell web framework. Alex Jacobson (a
haskeller of significant note, not some "clueless newbie") accidentally
wrote { length xs > 0 } instead of { not (null xs) } in some parsing
code. Which would just be inefficient, normally, but it demanded the
whole thing, which as it happened was a lazy stream coming of a socket.
Bad data dependencies, bang, deadlock.
Ouch! That's gotta sting...
I wasn't aware that this function was so leathal. I use it constantly
all the time...
Option 2. Ignore lists
It's possible to describe lists threaded with something else.
data ListT m a = m (ListT' m a)
data ListT' m a = NilT | ConsT a (ListT m a)
You get your safety back ... and lose the standard list functions, list
syntax, list comprehensions, list instances, strings-as-lists, et
cetera.
That's... interesting...
(I feel yet another "I'm going to have to sit down and think about that
one" comming on.)
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