clarify the naming convention for horizontal reductions, or lack thereof

Author: gnzlbg

text/0000-ppv.md

@@ -177,7 +177,7 @@ Operations on vector types can be either:
   For example, `a.sum()` adds the elements of a vector together while `a.hmax()`
   returns the largest element in a vector. These operations (typically)
   translate to a sequence of multiple SIMD instructions on most architectures
-  and are therefore slower. In many cases, they are, however, necessary.
+  and are therefore slower. In many cases, they are, however, necessary. 
 
 ## Example: Average
 
@@ -655,6 +655,15 @@ pub fn hmin(self) -> element_type;
 }
 ```
 
+Note: In this RFC, horizontal reductions are named according to the operation
+they perform. When this name clashes with that of a vertical operation, the
+horizontal reduction's name get's a `h`-prefix. In this case, the horizontal
+`max` and `min` reductions clash with the vertical `a.max(b)` operation, and
+therefore get a `h`-prefix. 
+
+An alternative would be to prefix all horizontal operations with, for example,
+the `h_`-prefix.
+
 #### Mask construction and element access
 
 ```rust