Re: [scala] vector math parameterized class in scala

>
> --j
>
> On Tue, Jul 7, 2009 at 6:57 PM, Kevin Wright <kev.lee.wright@...
> > wrote:
> You've also missed out on case classes and type inference, although  
> this isn't causing your problem...
>
> Using view bounds with the implicit conversions in Numeric should do  
> the trick!
>
> case class Vec3[T <:% Numeric] (x: T, y: T, z: T) {
>   def + (o: Vec3[T]) = new Vec3(x + o.x, y + o.y, z + o.z)
>   def * (s: T): Vec3[T] = new Vec3(x * s, y * s, z * s)
>   def len = x + y + z
>   def == (o: Vec3[T]) = x == o.x && y == o.y && z == o.z
>   def < (o: Vec3[T]) = x < o.x && y < o.y && z < o.z
> }
>
> On Tue, Jul 7, 2009 at 11:59 PM, Jorge Ortiz <jorge.ortiz@...>  
> wrote:
> Take a look at Scala 2.8's Numeric trait:
>
> http://lampsvn.epfl.ch/trac/scala/browser/scala/trunk/src/library/scala/Numeric.scala
>
> --j
>
>
> On Tue, Jul 7, 2009 at 5:56 PM, Jonathan Bachrach <jrb@...>  
> wrote:
> i see.  that's unfortunate.  how would you recommend writing a  
> vector math parameterized class in scala then (short of actually  
> copying the code)?
>
>
> On Jul 7, 2009, at 3:50 PM, Marcelo Fukushima wrote:
>
> i think the problem is that Number does not define '+' and '*' methods
> - and all the compiler knows about your T is that its a Number
> (java.lang.Number)
>
>
> On Tue, Jul 7, 2009 at 7:40 PM, Jonathan Bachrach<jrb@...>  
> wrote:
> i'm trying to define a vector math class using parameterized classes  
> in
> scala and am having trouble.  here's an abbreviated version of what  
> i wrote:
> class Vec3[T <: Number] (xa: T, ya: T, za: T) {
>  val x: T = xa; val y: T = ya; val z: T = za
>  def + (o: Vec3[T]): Vec3[T] = new Vec3(x + o.x, y + o.y, z + o.z)
>  def * (s: T): Vec3[T] = new Vec3(x * s, y * s, z * s)
>  def len (): T = x + y + z
>  def == (o: Vec3[T]): Boolean = x == o.x && y == o.y && z == o.z
>  def < (o: Vec3[T]): Boolean = x < o.x && y < o.y && z < o.z
> }
> and here's what scalac says:
> rala-692> scalac vec3.scala
> vec3.scala:3: error: type mismatch;
>  found   : T
>  required: String
>  def + (o: Vec3[T]): Vec3[T] = new Vec3(x + o.x, y + o.y, z + o.z)
>                                               ^
> vec3.scala:3: error: type mismatch;
>  found   : T
>  required: String
>  def + (o: Vec3[T]): Vec3[T] = new Vec3(x + o.x, y + o.y, z + o.z)
>                                                        ^
> vec3.scala:3: error: type mismatch;
>  found   : T
>  required: String
>  def + (o: Vec3[T]): Vec3[T] = new Vec3(x + o.x, y + o.y, z + o.z)
>                                                                 ^
> vec3.scala:4: error: value * is not a member of T
>  def * (s: T): Vec3[T] = new Vec3(x * s, y * s, z * s)
>                                     ^
> vec3.scala:4: error: value * is not a member of T
>  def * (s: T): Vec3[T] = new Vec3(x * s, y * s, z * s)
>                                            ^
> vec3.scala:4: error: value * is not a member of T
>  def * (s: T): Vec3[T] = new Vec3(x * s, y * s, z * s)
>                                                   ^
> vec3.scala:5: error: type mismatch;
>  found   : T
>  required: String
>  def len (): T = x + y + z
>                      ^
> vec3.scala:7: error: value < is not a member of T
>  def < (o: Vec3[T]): Boolean = x < o.x && y < o.y && z < o.z
>                                  ^
> 8 errors found
> i had added the T <: Number to try to make it so that the + would be
> compatible but it still thinks + only works with strings.  i'm not  
> even
> completely sure that Number is a real Scala Class.  i'm obviously not
> understanding how to write parameterized classes in scala.  any help  
> would
> be appreciated.
>
>
>
>
> --
> http://mapsdev.blogspot.com/
> Marcelo Takeshi Fukushima
>