- * performed on internal representations of points. Moreover, the second
- * argument to @add@ and @mul@ is guaranteed to be the output of @in@ or
- * @fix@.
+ * performed on internal representations of points.
+ *
+ * (Historical note. We used to guarantee that the second to @add@ and @mul@
+ * was the output of @in@ or @fix@, but this canonification turned out to
+ * make the precomputation in @ec_exp@ too slow. Projective implementations
+ * must therefore cope with a pair of arbitrary points.)