Name the output tuple elements (mn, mx)

Author: tkf

base/reduce.jl

@@ -763,15 +763,17 @@ Inf
 minimum(a; kw...) = mapreduce(identity, min, a; kw...)
 
 """
-    extrema(itr; [init]) -> Tuple
+    extrema(itr; [init]) -> (mn, mx)
 
-Compute both the minimum and maximum element in a single pass, and return them as a 2-tuple.
+Compute both the minimum `mn` and maximum `mx` element in a single pass, and return them
+as a 2-tuple.
 
 The value returned for empty `itr` can be specified by `init`. It must be a 2-tuple whose
 first and second elements are neutral elements for `min` and `max` respectively
 (i.e. which are greater/less than or equal to any other element). It is used for non-empty
-collections. Note: it implies that, for empty `itr`, the first element is typically
-_greater_ than the last element. This is a "paradoxical" but yet expected result.
+collections. Note: it implies that, for empty `itr`, the returned value `(mn, mx)` satisfies
+`mn ≥ mx` even though for non-empty `itr` it  satisfies `mn ≤ mx`.  This is a "paradoxical"
+but yet expected result.
 
 !!! compat "Julia 1.6"
     Keyword argument `init` requires Julia 1.6 or later.
@@ -791,16 +793,17 @@ julia> extrema([]; init = (Inf, -Inf))
 extrema(itr; kw...) = extrema(identity, itr; kw...)
 
 """
-    extrema(f, itr; [init]) -> Tuple
+    extrema(f, itr; [init]) -> (mn, mx)
 
-Compute both the minimum and maximum of `f` applied to each element in `itr` and return
-them as a 2-tuple. Only one pass is made over `itr`.
+Compute both the minimum `mn` and maximum `mx` of `f` applied to each element in `itr` and
+return them as a 2-tuple. Only one pass is made over `itr`.
 
 The value returned for empty `itr` can be specified by `init`. It must be a 2-tuple whose
 first and second elements are neutral elements for `min` and `max` respectively
 (i.e. which are greater/less than or equal to any other element). It is used for non-empty
-collections. Note: it implies that, for empty `itr`, the first element is typically
-_greater_ than the last element. This is a "paradoxical" but yet expected result.
+collections. Note: it implies that, for empty `itr`, the returned value `(mn, mx)` satisfies
+`mn ≥ mx` even though for non-empty `itr` it  satisfies `mn ≤ mx`.  This is a "paradoxical"
+but yet expected result.
 
 !!! compat "Julia 1.2"
     This method requires Julia 1.2 or later.