Really, arrays in Haskell are the most @#!$! confusing thing in the
world.
There's a bunch of different array structures.
I can't tell which one works best, and all I want to do is x[i] = value.
I thought uvector was the answer, you know, fast unboxed ARRAYs.
Imagine my surprise when I saw this
indexU :: UA e => UArr e -> Int -> e
O(n). indexU extracts an element out of an immutable unboxed array.
An array implementation with an order N lookup. huh ?? That's not an
array, that's a list. I was looking for an array.
However, I then found in the same hackage:
readMU :: MUArr e s -> Int -> ST s e
O(1). readMU reads the element at the specified index of a mutable
unboxed array.
So O(1) for mutable, but O(n) for immutable ? See, confusing... I'm
sure there's a really good, lofty type safety, something
or other reason for that, that I'm sure I don't care about ;-)
There's also ST. So why is there a uvector, when there's ST ??
etc, etc, etc...
and then there's monads...
other than that, having fun with haskell :-)
Brian
On Nov 3, 2009, at 3:42 PM, David Leimbach wrote:
On Tue, Nov 3, 2009 at 2:16 PM, Tracy Wadleigh <tracy.wadle...@gmail.com
> wrote:
I had to implement a ring buffer, and I wanted the code using it to
be written in Haskell. I ended up implementing the buffer in C, and
wrapping it in FFI from Haskell because implementing a destructive
array in Haskell is kind of unwieldy to someone of my experience
level. In Clean, it looks like the uniqueness typing allows for
destructive updates in a very controlled manner.
The ST monad provides this functionality. The never-instantiated-in-
a-visible-way state parameter of the ST monad provides the
"uniqueness" required for doing destructive updates in a pure way.
Someone suggested that to me on IRC once I'd already cranked out a C
implementation with FFI bindings. It's just too easy to use the FFI
in Haskell :-)
If we raise the barrier of FFI, more people will use ST!
Dave
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
