How to write this correct...

Ketil Malde ketil+haskell at
Sun Feb 22 21:00:53 EST 2004

HNBeck at (Hans Nikolaus Beck) writes:

> type GLVertex = (GLfloat,GLfloat,GLfloat)

>>  toVertex :: GLVertex -> Vertex3 GLfloat
>>  toVertex :: (a,a,a) -> Vertex3 a

> Yes this works (the first variant). Thanks ! But I must say that I
> have problems to understand 

The problem is that you tried to tell the compiler that toVertex would
return a parametrised type, namely 'Vertex3 a', but that the compiler
sees that toVertex, when given a 'GLVertex' always will produce
'Vertex3 GLfloat'.  

> the class mechanism in its full extend....

Classes doesn't have anything to do with this.

If I haven't seen further, it is by standing in the footprints of giants

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