Implements piping StringView into streams.

src/String/BasicStringView.hpp

@@ -1,5 +1,6 @@
 #ifndef ARBUTILS_BASICSTRINGVIEW_HPP
 #define ARBUTILS_BASICSTRINGVIEW_HPP
+#include <iostream>
 #include <string>
 
 namespace ArbUt {
@@ -28,7 +29,11 @@ namespace ArbUt {
         virtual constexpr bool operator!=(const std::string_view& rhs) const noexcept = 0;
         virtual constexpr bool operator==(const char* rhs) const noexcept = 0;
         virtual constexpr bool operator!=(const char* rhs) const noexcept = 0;
+
+        friend std::ostream& operator<<(std::ostream& out, const BasicStringView& c) {
+            out << c.c_str();
+            return out;
+        }
     };
 }
-
 #endif // ARBUTILS_BASICSTRINGVIEW_HPP