[Haskell-cafe] Are constructors strict?

Edward Z. Yang ezyang at MIT.EDU
Thu Jan 20 23:16:20 CET 2011

Hello Daryoush,

That is a good question, and depends on distinguishing between laziness
and nondeterminism.  Suppose I have a normal, lazily evaluated list:


There are thunks used in this case, but the end result is fully deterministic:
the next will always be 3, and then 4, and so on.  So thunks don't
give us nondeterminism; we need some other mechanism (whether it's another
list encoding the choices, or a more sophisticated backtracking monad.)


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