Delay formatter

Signed-off-by: James Cherry <cherry@parallaxsw.com>

Author: jjcherry56

include/sta/Delay.hh

@@ -28,6 +28,7 @@
 #include <cstddef>
 
 #include "StaConfig.hh"
+#include "Format.hh"
 #include "MinMax.hh"
 
 namespace sta {
@@ -356,4 +357,32 @@ Delay
 delayRemove(const Delay &delay1,
             const Delay &delay2);
 
-} // namespace
+} // namespace sta
+
+
+// Default formatter for Delay. delayAsString is preferred.
+#if defined(__cpp_lib_format) && __cpp_lib_format >= 201907L
+#include <format>
+
+namespace std {
+template <>
+struct formatter<sta::Delay> : formatter<std::string_view> {
+  auto format(const sta::Delay& delay, format_context& ctx) const {
+    std::string s = std::format("{:.3e}", delay.mean());
+    return formatter<std::string_view>::format(s, ctx);
+  }
+};
+}  // namespace std
+#else
+#include <fmt/core.h>
+
+namespace fmt {
+template <>
+struct formatter<sta::Delay> : formatter<std::string_view> {
+  auto format(const sta::Delay& delay, format_context& ctx) const {
+    return formatter<std::string_view>::format(
+        fmt::format("{:.3e}", delay.mean()), ctx);
+  }
+};
+}  // namespace fmt
+#endif