Re: [Haskell-cafe] Mutable but boxed arrays?
On Wed, 2007-09-05 at 20:37 +0200, Henning Thielemann wrote: Can someone explain me, why there are arrays with mutable but boxed elements? I, on the other hand, have always wondered why the strict arrays are called unboxed, rather than, well, strict? Strictness seems to be their observable property, while unboxing is just an (admittedly important) implementation optimization. I imagine that it'd be at least as easy to implement the strictness as the unboxedness for non-GHC compilers, and thus increase compatibility. -k ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mutable but boxed arrays?
On Wed, 5 Sep 2007, Jonathan Cast wrote: On Wed, 2007-09-05 at 20:37 +0200, Henning Thielemann wrote: Can someone explain me, why there are arrays with mutable but boxed elements? I thought that boxing is only needed for lazy evaluation. However if I access an element of an array that is the result of a sequence of in-place updates, all updates must be executed in order to get the final value. That is, the first access to an element of such an array evaluates all elements of the array I was imprecise here. With 'access' I meant an access to the array outside of the ST monad, that is on the result of runSTArray. No. A mutable array is mutable only in a monad (IO or ST), and updates happen within that monad. But they don't evaluate the values in the array at all, either the old value or the new one. They just move pointers to expressions in the heap around. 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 ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mutable but boxed arrays?
Ketil Malde wrote: On Wed, 2007-09-05 at 20:37 +0200, Henning Thielemann wrote: Can someone explain me, why there are arrays with mutable but boxed elements? I, on the other hand, have always wondered why the strict arrays are called unboxed, rather than, well, strict? Strictness seems to be their observable property, while unboxing is just an (admittedly important) implementation optimization. Unboxing is, unfortunately, observable: it is not so easy to make a strict array of SomeArbitraryAlgebraicDataType, because it's not in class Storable. Isaac ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] Mutable but boxed arrays?
Hello Isaac, Thursday, September 6, 2007, 9:41:34 PM, you wrote: Unboxing is, unfortunately, observable: it is not so easy to make a strict array of SomeArbitraryAlgebraicDataType, because it's not in class Storable. parallel arrays in GHC is just about it -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
