fix doc on sort.Slice

Author: jagprog5

src/sort/slice.go

@@ -9,15 +9,27 @@ import (
 	"math/bits"
 )
 
-// Slice sorts the slice x given the provided less function.
+// Slice sorts the slice x given the provided less function.  
 // It panics if x is not a slice.
 //
-// The sort is not guaranteed to be stable: equal elements
-// may be reversed from their original order.
+// The sort is not guaranteed to be stable: equal elements may be reversed from
+// their original order.  
 // For a stable sort, use [SliceStable].
 //
-// The less function must satisfy the same requirements as
-// the Interface type's Less method.
+// The less function reports whether the element with index i must sort before
+// the element with index j.
+//
+// If both less(i, j) and less(j, i) are false, then the elements at index i and
+// j are considered equal.
+//
+// The less function must satisfy strict weak ordering requirements. See
+// https://en.wikipedia.org/wiki/Weak_ordering#Strict_weak_orderings. In
+// contrast, [SliceStable] does not have as stringent requirements.
+//
+// Note that floating-point comparison (the < operator on float32 or float64
+// values) is not a transitive ordering when not-a-number (NaN) values are
+// involved. See Float64Slice.Less for a correct implementation for
+// floating-point values.
 //
 // Note: in many situations, the newer [slices.SortFunc] function is more
 // ergonomic and runs faster.