adl_begin, adl_end now takes auto &, and [[nodiscard]] index_valid

More consistent with std::ranges::begin

util.h

@@ -64,11 +64,11 @@ using oel::ssize;
 }
 
 
-/** @brief Check if index is valid (within bounds for operator[])
-*
+//! Returns true if index is within bounds (for operator[])
+/**
 * Requires that `r.size()` or `end(r) - begin(r)` is valid. */
 template< typename Integral, typename SizedRangeLike >
-constexpr bool index_valid(SizedRangeLike & r, Integral index)
+[[nodiscard]] constexpr bool index_valid(SizedRangeLike & r, Integral index)
 	{
 		static_assert( sizeof(Integral) >= sizeof _detail::Size(r) or std::is_unsigned_v<Integral>,
 			"Mismatched index type, please use a wider integer (or unsigned)" );
@@ -104,10 +104,10 @@ inline constexpr for_overwrite_t for_overwrite; //!< An instance of for_overwrit
 
 //! Same as `begin(range)` with a previous `using std::begin;`. For use in classes with a member named begin
 inline constexpr auto adl_begin =
-	[](auto && range) -> decltype(begin(range)) { return begin(range); };
+	[](auto & range) -> decltype(begin(range)) { return begin(range); };
 //! Same as `end(range)` with a previous `using std::end;`. For use in classes with a member named end
 inline constexpr auto adl_end =
-	[](auto && range) -> decltype(end(range)) { return end(range); };
+	[](auto & range) -> decltype(end(range)) { return end(range); };