specialization using RULES

[Simon Peyton-Jones]

| The rules do not fire. They only seem to fire if the specialized
| function is called directly, such as
|
| > doSomethingWith ( zipWith (-) (u :: Vec Three Double) v )

That's probably because to fire
        distance must be inlined
        but sumV and mapV must not
which is obviously a bit delicate.

To do that you need fairly fine grain control over exactly when inlining takes place. That's what the [n] part of an INLINE pragma is for.  Look in GHC.Base for examples.  Don and Duncan are experts.

I wish there was a more robust way to do this.

Simon