Ah! It seems that my wording was ambiguous. All I was trying to say is that
there is nothing you can do with an IO action which will cause an otherwise
pure expression to exhibit side effects during evaluation, *not* that an IO
action is observable in pure code or that they are arbitrarily manipula
On Fri, Aug 09, 2013 at 12:38:45AM +0700, Kim-Ee Yeoh wrote:
> On Thu, Aug 8, 2013 at 11:05 PM, Tom Ellis
> wrote:
> > On Thu, Aug 08, 2013 at 03:38:41PM +0200, Jerzy Karczmarczuk wrote:
> > > >One could simply implement IO as a free monad
> > > Interesting. I wonder how.
> >
> > See [1] for an e
On Thu, Aug 8, 2013 at 11:05 PM, Tom Ellis <
tom-lists-haskell-cafe-2...@jaguarpaw.co.uk> wrote:
> On Thu, Aug 08, 2013 at 03:38:41PM +0200, Jerzy Karczmarczuk wrote:
> > >One could simply implement IO as a free monad
> > Interesting. I wonder how.
>
> See [1] for an explanation of free monads in
On Thu, Aug 08, 2013 at 05:44:11PM +0100, Tom Ellis wrote:
> On Thu, Aug 08, 2013 at 06:25:12PM +0200, Daniel Trstenjak wrote:
> > > See [1] for an explanation of free monads in general. For IO in
> > > particular,
> > > define a functor
> > >
> > > data IOF a = GetChar (Char -> a) | PutChar
On Thu, Aug 08, 2013 at 06:25:12PM +0200, Daniel Trstenjak wrote:
> > See [1] for an explanation of free monads in general. For IO in particular,
> > define a functor
> >
> > data IOF a = GetChar (Char -> a) | PutChar Char a | ...
> >
> > with constructors for all elementary IO operations.
>
On Thu, Aug 08, 2013 at 05:23:50PM +0100, Oliver Charles wrote:
> On 08/08/2013 05:05 PM, Tom Ellis wrote:
> > On Thu, Aug 08, 2013 at 03:38:41PM +0200, Jerzy Karczmarczuk wrote:
> >>> One could simply implement IO as a free monad
> >> Interesting. I wonder how.
> >
> > See [1] for an explanation
Hi Tom,
> See [1] for an explanation of free monads in general. For IO in particular,
> define a functor
>
> data IOF a = GetChar (Char -> a) | PutChar Char a | ...
>
> with constructors for all elementary IO operations.
But how should this work if the user adds an IO operation, e.g by wr
On 08/08/2013 05:05 PM, Tom Ellis wrote:
> On Thu, Aug 08, 2013 at 03:38:41PM +0200, Jerzy Karczmarczuk wrote:
>>> One could simply implement IO as a free monad
>> Interesting. I wonder how.
>
> See [1] for an explanation of free monads in general
You're lacking a matching definition of [1] :)
On Thu, Aug 08, 2013 at 03:38:41PM +0200, Jerzy Karczmarczuk wrote:
> >One could simply implement IO as a free monad
> Interesting. I wonder how.
See [1] for an explanation of free monads in general. For IO in particular,
define a functor
data IOF a = GetChar (Char -> a) | PutChar Char a | .
I am sorry for having mixed-up arguments (but who throws the first
stone?...)
Jerzy seemed to suggest that the "impurity" of IO was somehow related to it
not supporting very many operations.
No, not really. I added
First, it is not true that you can do with, say, (printStr "Ho!" )
whatever
On Thu, Aug 08, 2013 at 08:41:25AM -0400, Jake McArthur wrote:
> I don't know what the denotation for this would be, but I can't think of
> any reasonable ones for which I can write (==) to respect the denotation.
> For example, is "set A, then set B" equal to "set B, then set A"?
[...]
I'm a bit
I don't know what the denotation for this would be, but I can't think of
any reasonable ones for which I can write (==) to respect the denotation.
For example, is "set A, then set B" equal to "set B, then set A"? Maybe you
could argue that they aren't operationally equivalent, but can you
guarantee
On Thu, Aug 08, 2013 at 11:38:08AM +0200, Jerzy Karczmarczuk wrote:
> Tom Ellis:
> >If I were writing a Haskell compiler I could certainly define 'IO' to be a
> >datatype that would allow me to compare 'putStr "c"' to itself. The
> >comparison could not be of operational equivalence, but it would
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