Ganesh Sittampalam wrote:
Every single call to newIORef, across the whole world, returns a
different ref.
How do you know? How can you compare them, except in the same Haskell
expression?
The "same" one as a previous one can only be returned
once the old one has become unused (and GCed).
Perhaps, but internally the IORef is a pointer value, and those pointer
values might be the same. From the same perspective, one could say that
every single call to newUnique across the whole world returns a
different value, but internally they are Integers that might repeat.
It's the scope in which values from newUnique are supposed to be
different, and it would also be the scope in which top-level <- would
be called at most once.
I don't really follow this. Do you mean the minimal such scope, or the
maximal such scope? The problem here is not about separate calls to
newIORef, it's about how many times an individual <- will be executed.
Two IO executions are in the same "global scope" if their resulting
values can be used in the same expression. Top-level <- declarations
must execute at most once in this scope.
--
Ashley Yakeley
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