From 35ae04510fdc9336ec1949dfe6701748c0cebfe6 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Wed, 1 May 2019 12:30:39 +1000
Subject: [PATCH] ascii: add try_lower

---
 ascii.hpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/ascii.hpp b/ascii.hpp
index b2cf627c..973fc253 100644
--- a/ascii.hpp
+++ b/ascii.hpp
@@ -131,6 +131,19 @@ namespace cruft::ascii {
     }
 
 
+    ///------------------------------------------------------------------------
+    /// Convert an ASCII character into a lower case character if it is upper
+    /// case, else return it unchanged.
+    ///
+    /// If you know the character is always upper case then prefer to_lower.
+    constexpr inline
+    char
+    try_lower (char c) noexcept
+    {
+        return is_upper (c) ? to_lower (c) : c;
+    }
+
+
     ///////////////////////////////////////////////////////////////////////////
     /// Returns true if the supplied ASCII character is whitespace.
     constexpr inline