Implement edit distance for StringRef

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92309 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/StringRef.h

@@ -133,6 +133,22 @@ namespace llvm {
     /// compare_lower - Compare two strings, ignoring case.
     int compare_lower(StringRef RHS) const;
 
+    /// \brief Determine the edit distance between this string and another 
+    /// string.
+    ///
+    /// \param Other the string to compare this string against.
+    ///
+    /// \param AllowReplacements whether to allow character
+    /// replacements (change one character into another) as a single
+    /// operation, rather than as two operations (an insertion and a
+    /// removal).
+    ///
+    /// \returns the minimum number of character insertions, removals,
+    /// or (if \p AllowReplacements is \c true) replacements needed to
+    /// transform one of the given strings into the other. If zero,
+    /// the strings are identical.
+    unsigned edit_distance(StringRef Other, bool AllowReplacements = true);
+
     /// str - Get the contents as an std::string.
     std::string str() const { return std::string(Data, Length); }