[Haskell-cafe] Re: Mutable but boxed arrays?

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 -> .. is not. Regards, apfelmus