+
+
+Other CPS transforms
+--------------------
+
+It is easy to think that CBN and CBV are the only two CPS transforms.
+(We've already seen a variant on call-by-value one of the excercises above.)
+
+In fact, the number of distinct transforms is unbounded. For
+instance, here is a variant of CBV that uses the same types as CBN:
+
+ <x> = x
+ <\xM> = \k.k(\x<M>)
+ <MN> = \k.<M>(\m.<N>(\n.m(\k.kn)k))
+
+Try reducing `<(\x.x) ((\y.y) (\z.z))> I` to convince yourself that
+this is a version of call-by-value.
+
+Once we have two evaluation strategies that rely on the same types, we
+can mix and match:
+
+ [x] = x
+ <x> = x
+ [\xM] = \k.k(\x<M>)
+ <\xM] = \k.k(\x[M])
+ [MN] = \k.<M>(\m.m<N>k)
+ <MN> = \k.[M](\m.[N](\n.m(\k.kn)k))
+
+This xform interleaves call-by-name and call-by-value in layers,
+according to the depth of embedding.
+