Changes in Hoopl

Jan Stolarek jan.stolarek at
Thu Aug 22 19:31:47 CEST 2013

Simon, you give this example:

   L1: ...blah blah...
       CondBranch e L1 L2

   L2: blah blah

and say that "(...) on the first iteration, we don't have any fact from L1. So for backwards analysis the client really must give us a bottom element. " I think this example does not actually demonstrate that we must have a bottom element, because if we have fact from L2 then we still don't need bottom in the same way we don't need it in forward analysis. We need bottom only when all entry facts are unknown.


----- Oryginalna wiadomość -----
Od: "Simon Peyton-Jones" <simonpj at>
Do: "Simon Marlow" <marlowsd at>, "Jan Stolarek" <jan.stolarek at>
DW: "ghc-devs" <ghc-devs at>, nr at, dias at, "Edward Z. Yang" <ezyang at>
Wysłane: czwartek, 22 sierpień 2013 17:44:11
Temat: RE: Changes in Hoopl

I have elaborated (more clearly I hope)


| -----Original Message-----
| From: Simon Marlow [mailto:marlowsd at]
| Sent: 22 August 2013 15:14
| To: Jan Stolarek
| Cc: ghc-devs; Simon Peyton-Jones; nr at; dias at;
| Edward Z. Yang
| Subject: Re: Changes in Hoopl
| Hi Jan,
| On 22/08/13 14:01, Jan Stolarek wrote:
| > Me and Simon PJ had some discussion about modifying Hoopl. I
| summarized that discussion on a wiki page:
| >
| >
| >
| > I'd like to implement changes once there's a consensus on which
| changes exactly do we want in Hoopl.
| I'm all for cleaning up Hoopl.  It's definitely a bit of a mess in
| places.
| I read through your wiki page and I'm not entirely clear about what
| changes you're proposing.  e.g. it's probably true that in forward
| analysis if you specify facts for all the input labels then fact_bot is
| never used (though I'm not 100% sure about that).  But you don't say
| what you want to do with that observation.  Could you list the API
| changes you want to make?
| Cheers,
| 	Simon

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