Quoting Jesper Louis Andersen <jlouis@mongers.org>:
> datatype ('a, 'b) either = INL of 'a
> | INR of 'b
I like this one. Now that I think about it, I recall seeing this
naming used somewhere (article or book).
The "IN" part also nicely suggests the antonym for the occasionally
useful partial destructors:
fun outL (INL x) = x
fun outR (INR x) = x
-Vesa Karvonen