Thanks - I'll take a look. One pre-emptive question: if I want to use it, it'd be more convenient, though not insurmountable, if that code was BSD3-licenced, since it will fit in better with the licence for camp http://projects.haskell.org/camp, which I might eventually want to integrate my code into. (the predicates I described are intended to be the commutation conditions for patches). Is that likely to be possible? Cheers, Ganesh On Fri, 5 Dec 2008, Immanuel Normann wrote:
Hi,
you can browse my code here.http://trac.informatik.uni-bremen.de:8080/hets/browser/trunk/Search/CommonIt has become part of Hets http://www.dfki.de/sks/hets the Heterogeneous Tool Set which is a parsing, static analysis and proof management tool combining various tools for different specification languages. However, let me warn you: the code isn't yet well documented at parts also ad hoc. Don't know whether it can help to solve your tasks. The goal of my normalization code is to bring formulae via equivalence transformations and alpha-renaming into a standard or normal form such that for instance the following three formulae become syntactically identical (i.e. not just modulo alpha equivalence or modulo associativity and commutativity):
\begin{enumeratenumeric} \item $\forall \varepsilon . \varepsilon > 0 \Rightarrow \exists \delta . \forall x. \forall y. 0 < |x - y| \wedge |x - y| < \delta \Rightarrow | f (x) - f (y) | < \varepsilon$
\item $\forall \varepsilon . \exists \delta . \forall x, y. \varepsilon > 0 \Rightarrow (0 < |x - y| \wedge |x - y| < \delta \Rightarrow | f (x) - f (y) | < \varepsilon)$
\item $\forall e . \exists d . \forall a,b. e > 0 \wedge |a - b| < d \wedge 0 < |a - b| \Rightarrow | f (a) - f (b) | < e$ \end{enumeratenumeric}
Cheers,
Immanuel
2008/12/4 Ganesh Sittampalam
Hi,
That sounds like it might be quite useful. What I'm doing is generating some predicates that involve addition/subtraction/comparison of integers and concatenation/comparison of lists of some abstract thing, and then trying to simplify them. An example would be simplifying
\exists p_before . \exists p_after . \exists q_before . \exists q_after . \exists as . \exists bs . \exists cs . (length p_before == p_pos && length q_before == q_pos && (p_before == as && q_after == cs) && p_before ++ p_new ++ p_after == as ++ p_new ++ bs ++ q_old ++ cs && as ++ p_new ++ bs ++ q_old ++ cs == q_before ++ q_old ++ q_after)
into
q_pos - (p_pos + length p_new) >= 0
which uses some properties of length as well as some arithmetic. I don't expect this all to be done magically for me, but I'd like as much help as possible - at the moment I've been growing my own library of predicate transformations but it's all a bit ad-hoc.
If I could look at your code I'd be very interested.
Cheers,
Ganesh
On Thu, 4 Dec 2008, Immanuel Normann wrote:
Hi Ganesh,
manipulating predicate formulae was a central part of my PhD research. I implemented some normalization and standarcization functions in Haskell - inspired by term rewriting (like normalization to Boolean ring representation) as well as (as far as I know) novell ideas (standardization of quantified formulae w.r.t associativity and commutativity). If you are interested in that stuff I am pleased to provide you with more information. May be you can describe in more detail what you are looking for.
Best, Immanuel
2008/11/30 Ganesh Sittampalam
Hi,
Are there any Haskell libraries around for manipulating predicate formulae? I had a look on hackage but couldn't spot anything.
I am generating complex expressions that I'd like some programmatic help in simplifying.
Cheers,
Ganesh _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe