-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 8/24/10 01:38 , Greg Best wrote:
The part I figured was impractical was the "Angular" class, but this is the second feedback that suggested making both Degrees and Radians type constructors rather than alternate value constructors. Is that the right approach? I know the trig functions are already available and they all just traffic in floats, but if this weren't the case, I'd imagine a structure along the lines of
The point of typeclasses is to allow you to abstract operations over multiple types. If you have only one type...
data Angle a = Radians a | Degrees a deriving (Eq, Show)
then a typeclass is just unnecessary complexity. It's when you have multiple types which share a group of operations that typeclasses become useful. So, for example, with the above type (sin) can be implemented as a single function which pattern matches on the constructor; but if (Radians) and (Degrees) need to be separate types instead of value constructors for a single type, then you *must* use a typeclass to implement a single (sin) instead of (sinRadians) or (sinDegrees). - -- brandon s. allbery [linux,solaris,freebsd,perl] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.10 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkxzXyMACgkQIn7hlCsL25UfdgCgnx492P1aLyttxTsTQKBycSlf KvQAnA/FkXYgPpJP37aF2hoJCMWUct+I =aldW -----END PGP SIGNATURE-----