On 2006-02-16, Claus Reinke
Oh golly. I can't live without pattern guards. they are the best darn thing since sliced bread. I highly recommend them. I .. would have to seriously refactor a ton of code if pattern guards disapeared.
So much so that it would be less work to implement pattern guards for other compilers and submit the patches.
eh, well, pattern guards are nice. but, many of their uses are also easily replaced, by moving the pg-monad from the lhs to the rhs, and employing MonadPlus for the fall-throughs; something roughly like:
f p1 | g1 = e1 .. f pn | gn = en where <stuff>
-->
f x = fromJust $ do {p1 <- return x; guard g1; return e1} .. `mplus` do {pn <- return x; guard gn; return en} where <stuff>
This works, of course, but it looks far far uglier, and is harder to type. -- Aaron Denney -><-