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You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Beginners digest..." Today's Topics: 1. Re: [Haskell-cafe] Re: [Haskell-beginners] Re: Accounting Engine in Haskell (Patrick LeBoutillier) 2. Re: [Haskell-cafe] Re: [Haskell-beginners] Re: Accounting Engine in Haskell (Stephen Tetley) 3. Re: [Haskell-cafe] Re: [Haskell-beginners] Re: Accounting Engine in Haskell (Stephen Tetley) ---------------------------------------------------------------------- Message: 1 Date: Thu, 17 Jun 2010 14:40:14 -0400 From: Patrick LeBoutillier <patrick.leboutill...@gmail.com> Subject: Re: [Haskell-cafe] Re: [Haskell-beginners] Re: Accounting Engine in Haskell To: Stephen Tetley <stephen.tet...@gmail.com> Cc: beginners@haskell.org Message-ID: <aanlktil7klytchr3pv0alltp29en-cov76bdszkhp...@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Thanks, I'll try to look it up. I have a question about the representation. In the paper, the authors define a Region as: type Region = Point -> Bool type Point = (Float,Float) I understand the idea that representing Regions as functions is quite interesting when it comes to combining and manipulating them. But what if one wants to calculate the area of a Region or render it in some fashion? Thanks, Patrick On Thu, Jun 17, 2010 at 11:24 AM, Stephen Tetley <stephen.tet...@gmail.com> wrote: > On 17 June 2010 16:12, Patrick LeBoutillier > <patrick.leboutill...@gmail.com> wrote: > >> This paper was very interesting to me. Does anyone know if the full source >> code >> for the Haskell prototype is available somewhere? > > Chapter 8 of Paul Hudak's School of Expression contains a version of > the "region algebra", there's also an ML version by Samuel Kamin where > the region combinators generate C++ code: > > Samuel Kamin - Standard ML as a Meta-Programming Language: > > http://loome.cs.uiuc.edu/pubs.html > http://loome.cs.uiuc.edu/pubs/ml-meta.pdf > _______________________________________________ > Haskell-Cafe mailing list > haskell-c...@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- ===================== Patrick LeBoutillier Rosemère, Québec, Canada ------------------------------ Message: 2 Date: Thu, 17 Jun 2010 19:58:36 +0100 From: Stephen Tetley <stephen.tet...@gmail.com> Subject: Re: [Haskell-cafe] Re: [Haskell-beginners] Re: Accounting Engine in Haskell To: Patrick LeBoutillier <patrick.leboutill...@gmail.com> Cc: beginners@haskell.org Message-ID: <aanlktilgwpoeyxagzaixr7jom9ext7uvah1ozie1n...@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Hi Patrick Rendering is easy - Region is a characteristic function - so apply it to all the coordinates in a bitmap (i.e. indexes in a 2D array) - you'll get a black-and-white picture. Conal Elliott's Pan and Jerzy Karczmarczuk's Clastic do this with an extend "colour characteristic" function -@ type Picture = Point -> RGB @- to make colour bitmaps rather than b&w ones. Area, I'm not sure about. Maybe you good integrate the function through a space, but this might not be a good idea. Best wishes Stephen ------------------------------ Message: 3 Date: Thu, 17 Jun 2010 20:12:04 +0100 From: Stephen Tetley <stephen.tet...@gmail.com> Subject: Re: [Haskell-cafe] Re: [Haskell-beginners] Re: Accounting Engine in Haskell Cc: beginners@haskell.org Message-ID: <aanlktilcjscjhqvhacyvexe43gkwqc8xce1tn3x14...@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 On 17 June 2010 19:58, Stephen Tetley <stephen.tet...@gmail.com> wrote: ... > Area, I'm not sure about. Maybe you **good** integrate the function > through a space, but this might not be a good idea. Ahem, swap 'good' for 'could' in that bit... Antony Courtney used a dual representation for his vector graphics program - Haven. Images were both a "colour characteristic function" and proper/plain characteristic function for regions. I think this was so that "point in polygon" calculations could be made easily. type Image = (Point -> Color, Region) Perhaps, it might not be too much of a stretch to model regions both with a characteristic function and a more concrete representation that allows area to be taken more easily. The region combinators would become more complicated though. ------------------------------ _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 24, Issue 20 *****************************************