Explain the need for double backslashes.
Change-Id: Ibe3f58504635b1e60692457b8ce1b14e700015ef
Reviewed-on: https://code-review.googlesource.com/c/re2/+/55150
Reviewed-by: Paul Wankadia <junyer@google.com>
diff --git a/re2/re2.h b/re2/re2.h
index 8dee246..32b2718 100644
--- a/re2/re2.h
+++ b/re2/re2.h
@@ -30,6 +30,16 @@
// "(?i)hello" -- (?i) turns on case-insensitive matching
// "/\\*(.*?)\\*/" -- .*? matches . minimum no. of times possible
//
+// The double backslashes are needed when writing C++ string literals.
+// However, they should NOT be used when writing C++11 raw string literals:
+//
+// R"(hello (\w+) world)" -- \w matches a "word" character
+// R"(version (\d+))" -- \d matches a digit
+// R"(hello\s+world)" -- \s matches any whitespace character
+// R"(\b(\w+)\b)" -- \b matches non-empty string at word boundary
+// R"((?i)hello)" -- (?i) turns on case-insensitive matching
+// R"(/\*(.*?)\*/)" -- .*? matches . minimum no. of times possible
+//
// -----------------------------------------------------------------------
// MATCHING INTERFACE:
//
