xml in fptools?

Malcolm Wallace Malcolm.Wallace at cs.york.ac.uk
Fri May 26 11:44:12 EDT 2006

Simon Marlow <simonmarhaskell at gmail.com> wrote:

> >I'm not even certain that lazy I/O doesn't upset referential 
> >transparency.  
> >               ... the act of evaluating that thunk
> >might affect the value of another lazy I/O computation, and hence
> >it should be possible to get different results by evaluating the
> >thunks in a different order.
> It might be possible to construct  an example using pipes, though.

Haskell program output is piped to a process which feeds the Haskell
program's input pipe.  External process computes the time it takes for
successive items to appear on its input.  Voila, the input to Haskell
land is dependent on how long it takes to generate its output, and
therefore (indirectly) on evaluation order.

It's a bit contrived, and I'm not sure it really breaks ref trans
either.  This kind of feedback oscillator might have interesting chaotic
behaviour though!


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