Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org
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. How long is the pointer from a Vector valid (after it has been extracted by unsafeWidth) (Nathan H?sken) 2. Re: How to convert a float or double number into a string? (Kim-Ee Yeoh) 3. question about pattern guards (TP) 4. Re: How to convert a float or double number into a string? (yi lu) 5. Inverse trig functions (Adrian May) 6. Re: Inverse trig functions (Martin Ruderer) 7. Re: Inverse trig functions (Adrian May) 8. Re: Inverse trig functions (Martin Ruderer) ---------------------------------------------------------------------- Message: 1 Date: Thu, 19 Sep 2013 14:26:57 +0200 From: Nathan H?sken <nathan.hues...@posteo.de> To: beginners@haskell.org Subject: [Haskell-beginners] How long is the pointer from a Vector valid (after it has been extracted by unsafeWidth) Message-ID: <523aed91.9090...@posteo.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Hey, Background: I am making a wxhaskell backend for diagrams. Currently I am attempting to implement dashing. The function penSetDashes :: Pen a -> Int -> Ptr c -> IO () takes a bit muster, represented by an array of chars (second parameter is the number of the used bits). The problem is, that the underlying C++ function expects the pointer to be valid even after the function has been executed (until the pen is deleted or another dashing is set). So I am creating a Vector Word8 with the desired bitmuster and I am using Data.Vector.Storable.withUnsafe to pass its internal pointer to penSetDashes. But the pointer must point to something valid even after that! So I was thinking, what if I define data MyPen a = MyPen (Pen a) (Vector Word8) and always keep the vector of dashes with the pen. Will the pointer stay valid? If there are other Ideas on how to this, I am open! Regards, Nathan ------------------------------ Message: 2 Date: Thu, 19 Sep 2013 23:39:41 +0700 From: Kim-Ee Yeoh <k...@atamo.com> To: The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell <beginners@haskell.org> Subject: Re: [Haskell-beginners] How to convert a float or double number into a string? Message-ID: <capy+zdrds97btri4wrnlh_ko4lvu4hpvh3rsq0uvpemh5rx...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" On Wed, Sep 18, 2013 at 8:14 PM, yi lu <zhiwudazhanjiang...@gmail.com>wrote: > What I need is just as much number of digits as possible. If I can hold as > many digits of pi, i.e. 3.1415926535... as possible and save it in a > String, it will be perfect! > Perhaps you had some experience with a computer algebra system (Maple, Mathematica, etc.) and was expecting similar behavior? While it's certainly possible to build it on top of Haskell, these kind of floating-point features aren't available out of the box. Haskell provides only fixed-bitwidth floating point. As Oscar recommended, you probably want a String -> String function, say > toEnglish "1.239402874" "one point two three nine four zero blah blah" -- Kim-Ee -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130919/92271c32/attachment-0001.html> ------------------------------ Message: 3 Date: Fri, 20 Sep 2013 00:20:45 +0200 From: TP <paratribulati...@free.fr> To: beginners@haskell.org Subject: [Haskell-beginners] question about pattern guards Message-ID: <tu9sga-1mo.ln1@rama.universe> Content-Type: text/plain; charset="ISO-8859-1" Hi, I have a question related to pattern guards in the syntax of Haskell 2010. Why is it not possible to combine them with a logical OR, instead of the comma that stands for a logical AND? http://www.haskell.org/ghc/docs/latest/html/users_guide/syntax-extns.html#pattern-guards Thanks, TP ------------------------------ Message: 4 Date: Fri, 20 Sep 2013 08:44:50 +0800 From: yi lu <zhiwudazhanjiang...@gmail.com> To: The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell <beginners@haskell.org> Subject: Re: [Haskell-beginners] How to convert a float or double number into a string? Message-ID: <cakcmqqxy1nz-+x7ezpnxejbpzumcq-ahqlpnivy7gk0a1x-...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" Thank you all! I am considering defining a String -> String function now. On Fri, Sep 20, 2013 at 12:39 AM, Kim-Ee Yeoh <k...@atamo.com> wrote: > > On Wed, Sep 18, 2013 at 8:14 PM, yi lu <zhiwudazhanjiang...@gmail.com>wrote: > >> What I need is just as much number of digits as possible. If I can hold >> as many digits of pi, i.e. 3.1415926535... as possible and save it in a >> String, it will be perfect! >> > > Perhaps you had some experience with a computer algebra system (Maple, > Mathematica, etc.) and was expecting similar behavior? > > While it's certainly possible to build it on top of Haskell, these kind of > floating-point features aren't available out of the box. Haskell provides > only fixed-bitwidth floating point. > > As Oscar recommended, you probably want a String -> String function, say > > > toEnglish "1.239402874" > "one point two three nine four zero blah blah" > > -- Kim-Ee > > _______________________________________________ > Beginners mailing list > Beginners@haskell.org > http://www.haskell.org/mailman/listinfo/beginners > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130920/cd557eae/attachment-0001.html> ------------------------------ Message: 5 Date: Fri, 20 Sep 2013 18:11:42 +0800 From: Adrian May <adrian.alexander....@gmail.com> To: "beginners@haskell.org" <beginners@haskell.org> Subject: [Haskell-beginners] Inverse trig functions Message-ID: <cad-ubzhk9xtm-mtvp_awkq+arp2knlek93tfrtyvbr0joxv...@mail.gmail.com> Content-Type: text/plain; charset="utf-8" Hi All, When Haskell says "inverse trig function", it seems to mean the inverse of the return value of a trig function. I want those functions that return an angle whose sine, cosine or whatever equals the parameter I pass. Where are those? TIA, Adrian. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130920/b3fd6f4e/attachment-0001.html> ------------------------------ Message: 6 Date: Fri, 20 Sep 2013 13:40:00 +0200 From: Martin Ruderer <martin.rude...@gmail.com> To: The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell <beginners@haskell.org> Subject: Re: [Haskell-beginners] Inverse trig functions Message-ID: <ca+t_wnajeuvvl9xytfrnd9yr6h9fhqw9xkvmitgkiy-wdu7...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" Hello Adrian, those would be called asin and acos. Best regards, Martin -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130920/a75a1e84/attachment-0001.html> ------------------------------ Message: 7 Date: Fri, 20 Sep 2013 19:52:34 +0800 From: Adrian May <adrian.alexander....@gmail.com> To: The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell <beginners@haskell.org> Subject: Re: [Haskell-beginners] Inverse trig functions Message-ID: <cad-ubzgvv6b1kh+-okprlwqxwfo7ax1iv+y1vzfmdtyyrxa...@mail.gmail.com> Content-Type: text/plain; charset="utf-8" Apparently not. Those are 1/sin and 1/cos. I want to supply a ratio and get an angle. On 20 September 2013 19:40, Martin Ruderer <martin.rude...@gmail.com> wrote: > Hello Adrian, > > those would be called asin and acos. > > Best regards, > Martin > > > _______________________________________________ > Beginners mailing list > Beginners@haskell.org > http://www.haskell.org/mailman/listinfo/beginners > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130920/c7c0816a/attachment-0001.html> ------------------------------ Message: 8 Date: Fri, 20 Sep 2013 13:59:50 +0200 From: Martin Ruderer <martin.rude...@gmail.com> To: The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell <beginners@haskell.org> Subject: Re: [Haskell-beginners] Inverse trig functions Message-ID: <CA+t_wNBjMZaoHpRsWBrgVUH8hoi+VYMra=qyjuc8m88wttw...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" Are you sure? Prelude> map (sin.asin) [0.1,0.3,0.5,0.7,0.9] [0.1,0.3,0.5,0.7,0.9] On Fri, Sep 20, 2013 at 1:52 PM, Adrian May <adrian.alexander....@gmail.com>wrote: > Apparently not. Those are 1/sin and 1/cos. I want to supply a ratio and > get an angle. > > > On 20 September 2013 19:40, Martin Ruderer <martin.rude...@gmail.com>wrote: > >> Hello Adrian, >> >> those would be called asin and acos. >> >> Best regards, >> Martin >> >> >> _______________________________________________ >> Beginners mailing list >> Beginners@haskell.org >> http://www.haskell.org/mailman/listinfo/beginners >> >> > > _______________________________________________ > Beginners mailing list > Beginners@haskell.org > http://www.haskell.org/mailman/listinfo/beginners > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130920/a3b498fb/attachment.html> ------------------------------ Subject: Digest Footer _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners ------------------------------ End of Beginners Digest, Vol 63, Issue 28 *****************************************