[Haskell-cafe] Re: Mutable but boxed arrays?
apfelmus at quantentunnel.de
Thu Sep 6 09:12:00 EDT 2007
Henning Thielemann wrote:
> I'll see, if I understand it.
> do writeArray arr 0 2
> x <- readArray arr 0
> writeArray arr 0 (x+x)
> If 'arr' is an STArray, the 'arr' will contain the unevaluated
> expression "2+2" as zeroth element and with type STUArray it will
> contain the evaluated "4" ?
Exactly. Put differently,
writeArray :: STUArray -> ..
is strict in the third argument whereas
writeArray :: STArray -> ..
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