Re: [Haskell-cafe] ANN: vector-buffer package 0.1

Hi Luke, Apologies, I think I got bitten by unsafePerformIO. The reason it wasn't in the IO monad is that the Vector created from the Buffer is supposed to be immutable. I've changed the API so that: main = do buf <- newBuffer 10 :: IO (Buffer Int) pushNextElement buf 1 v1 <- toVector buf v2 <- toVector buf print $ V.toList v1 pushNextElement buf 2 print $ V.toList v2 does as expected. Thanks, Vivian On 15 February 2011 17:08, Luke Palmer wrote:

This interface is an outlaw.

main = do buf <- newBuffer 10 :: IO (Buffer Int) pushNextElement buf 1 let v1 = V.toList (toVector buf) v2 = V.toList (toVector buf) print v1 pushNextElement buf 2 print v2

Despite v1 and v2 being defined to equal the exact same thing, this program prints two distinct lines.

toVector depends on the current state of the buffer. If this is to be a law-abiding interface, toVector must return a value in IO:

toVector :: (Storable a) => Buffer a -> IO (Vector a)

Luke

On Mon, Feb 14, 2011 at 7:28 PM, Alexander McPhail wrote:

...

Hi,

I have uploaded a small package, vector-buffer, to hackage. It provides a buffer that can be turned into a Data.Vector.Storable. The mapM* functions map from the oldest element, not the first. Similarly for the derived Vector.

Feature requests etc. welcome.

Vivian

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