I thought the types were *existentially* quantified because the
constructor arguments were *universally* quantified. Or did I get it
backwards?
Dan
Wolfgang Jeltsch wrote:
Am Mittwoch, 30. Mai 2007 14:09 schrieb Brandon S. Allbery KF8NH:
On May 30, 2007, at 5:59 , Federico Squartini wrote:
I suppose there is something "under the hood" which makes them
different, but I cannot figure out what.
For one thing, ST uses existential types to prevent values from
leaking outside the monad.
ST uses universally-quantified types.
Also note that an important difference between State and ST is that State can
be implemented in pure Haskell while ST has to be hard-wired into the
compiler/interpreter or implemented in Haskell using unsafe features.
Best wishes,
Wolfgang
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