add fmt support if fmt/ostream.h is found

include/cista/containers/bitset.h

@@ -300,3 +300,12 @@ struct bitset {
 };
 
 }  // namespace cista
+
+#if __has_include("fmt/ostream.h")
+
+#include "fmt/ostream.h"
+
+template <std::size_t Size>
+struct fmt::formatter<cista::bitset<Size>> : ostream_formatter {};
+
+#endif

include/cista/containers/string.h

@@ -444,3 +444,12 @@ using string_view = basic_string_view<ptr<char const>>;
 }  // namespace offset
 
 }  // namespace cista
+
+#if __has_include("fmt/ostream.h")
+
+#include "fmt/ostream.h"
+
+template <typename Ptr>
+struct fmt::formatter<cista::basic_string<Ptr>> : ostream_formatter {};
+
+#endif

include/cista/indexed.h

@@ -21,3 +21,12 @@ template <class T>
 constexpr bool is_indexed_v = is_indexed_helper<std::remove_cv_t<T>>::value;
 
 }  // namespace cista
+
+#if __has_include("fmt/ostream.h")
+
+#include "fmt/ostream.h"
+
+template <typename T>
+struct fmt::formatter<cista::indexed<T>> : ostream_formatter {};
+
+#endif

include/cista/strong.h

@@ -196,3 +196,12 @@ struct hash<cista::strong<T, Tag>> {
 };
 
 }  // namespace std
+
+#if __has_include("fmt/ostream.h")
+
+#include "fmt/ostream.h"
+
+template <typename T, typename Tag>
+struct fmt::formatter<cista::strong<T, Tag>> : ostream_formatter {};
+
+#endif