On Sun, Jun 16, 2013 at 10:42 PM, <bri...@aracnet.com> wrote:
> On Sun, 16 Jun 2013 16:15:25 -0400 > Brandon Allbery <allber...@gmail.com> wrote: > > > On Sun, Jun 16, 2013 at 4:03 PM, <bri...@aracnet.com> wrote: > > > > > Changing the declaration to GLdouble -> GLdouble -> GLdouble -> IO() > and > > > using > > > (0.0::GLdouble) fixes it, and I'm not clear on why it's not automagic. > > > There are many times I see the > > > > > > Haskell never "automagic"s types in that context; if it expects GLdouble, > > it expects GLdouble. Pretending it's Double will not work. It "would" in > > the specific case that GLdouble were actually a type synonym for Double; > > however, for performance reasons it is not. Haskell Double is not > directly > > usable from the C-based API used by OpenGL, so GLdouble is a type synonym > > for CDouble which is. > > > > compiler doing type conversion an numerican arguments although sometimes > > > the occasional fracSomethingIntegralorOther is required. > > > > > > > I presume the reason the type specification for numeric literals is > because > > there is no defaulting (and probably can't be without introducing other > > strange type issues) for GLdouble. > > > > What I was thinking about, using a very poor choice of words, was this : > > > *Main> let a = 1 > *Main> :t a > a :: Integer > *Main> let a = 1::Double > *Main> a > 1.0 > *Main> :t a > a :: Double > *Main> > > so normally 1 would be interpreted as an int, but if I declare 'a' a > Double then it gets "promoted" to a Double without me having to call a > conversion routine explicitly. > > That seems automagic to me. > > (0.0::GLdouble) works to make the compiler happy. So it appears to be > taking care of the conversion automagically. > > So maybe a better question, I hope, is: > > How can I simply declare 0.0 to be (0.0::GLdouble) and have the functional > call work. Doesn't a conversion have to be happening, i.e. shouldn't I > really have to do (realToFrac 0.0) ? > > Brian > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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