Re: [scala] vector math parameterized class in scala

> 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