[Haskell-cafe] Lisp like symbols in haskell
lrpalmer at gmail.com
Tue Dec 8 04:01:25 EST 2009
On Tue, Dec 8, 2009 at 1:48 AM, Michael Vanier <mvanier42 at gmail.com> wrote:
> Do you mean symbols as in "interned strings with an O(1) string comparison
> method"? I would love to have those, but I don't see an easy way to get it
> without being in the IO or ST monad.
data Sym = Sym String Hash
fromString :: String -> Sym
fromString s = Sym s (hash s)
instance Eq Sym where
Sym _ h == Sym _ h' = h == h'
Much as I am uncomfortable with hash-based equality. 1/2^256, despite
being very small, is not zero. It is begging for a mysterious failure
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