Donald Bruce Stewart
The joy of pattern guards reveals once you have more conditions.
I wrote:
Of course, this is not really the joy of pattern guards. It is the joy of monads, with perhaps a few character strokes saved by a confusing overloading of (<-).
Philippa Cowderoy wrote:
I don't find it any more confusing than the overloading of ->.
You mean that it is used both for lambda abstractions and for functional dependencies? True, but those are so different that there is no confusion.
Note that it's not (<-) - it's not an operator.
Right, it is syntactic sugar for a monad. But this syntax is already used in two places: do notation and list comprehensions. The semantics are exactly the same in both existing uses. The semantics of the proposed new use in pattern guards is quite different, as was discussed in the previous thread. Yet close enough to be confused. There seems to be a consensus that pattern guards are here to stay. So I am proposing to mitigate the damage somewhat by using a different but similar symbol . That matches the different but similar semantics. I mentioned (<<-) as one possibility. Regards, Yitz