Binary question

[Hal Daume III]

There are a few Binarys for GHC out there; I'm not sure which one you're
using, but the one I use (that compiles fine) you can grab from me at:

  http://www.isi.edu/~hdaume/hnlp/Binary.hs (you'll also need
hnlp/FastMutInt.lhs)

>   In the meantime i have a temporary version of binary but its
> performance is not what i would like. Let me paste some of it
>   
> [snip]

This is certainly not the same as the one I'm using.  I don't know if mine
is compatible with DrIFT (or whatever the appropriate capitalization is),
but it's really quite trivial to write your own instances.  An instance
for FiniteMap is:

> instance (Ord a, Binary a, Binary b) => Binary (FiniteMap a b) where
>     put_ bh = put_ bh . fmToList
>     get  bh = get bh >>= return . listToFM

The most unfortunate thing I found with this version of Binary is that
there's not as built in instance of Binary Double.  My instance is:

> instance Binary Double where
>     put_ bh d = put_ bh (doubleToInts d)
>     get  bh   = get bh >>= return . intsToDouble

Where the appropriate (admittedly hack) definitions used in there are:

> doubleToInts d = runST (
>     do arr <- newDoubleArray (1,2)
>        writeDoubleArray arr 1 d
>        i1 <- readIntArray arr 1
>        i2 <- readIntArray arr 2
>        return (i1,i2))
> 
> intsToDouble (i1,i2) = runST (
>     do arr <- newDoubleArray (1,2)
>        writeIntArray arr 1 i1
>        writeIntArray arr 2 i2
>        readDoubleArray arr 1)

>   My second question is how to optimize this piece of code. I suppose
> that the main performance bottleneck is the use of hPutChar. I did some
> profiling but some guidance will be really helpful.

I'll let someone else take that :)