Suggestion for bang patterns documentation
simonpj at microsoft.com
Fri Feb 27 06:22:49 EST 2009
| The let-binding can be recursive. However, it is much more common for
| the let-binding to be non-recursive, in which case the following law
| holds: (let !p = rhs in body) is equivalent to (case rhs of !p -> body)
| Shouldn't the bang be removed in the final case pattern?
No. If p was a simple variable, then
case rhs of x -> body
is non-strict in Haskell, but should be strict here.
| P.S. It should be mentioned that ~ and ! only make sense for single
| variant data types (like tuples)
That isn't true. Both are useful for multi-variant types
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