[llvm-commits] [llvm] r92309 - in /llvm/trunk: include/llvm/ADT/StringRef.h lib/Support/StringRef.cpp

[Douglas Gregor]

Sent from my iPhone

On Dec 30, 2009, at 2:44 PM, Daniel Dunbar <daniel at zuster.org> wrote:

> On Wed, Dec 30, 2009 at 9:23 AM, Douglas Gregor <dgregor at apple.com>  
> wrote:
>> Author: dgregor
>> Date: Wed Dec 30 11:23:44 2009
>> New Revision: 92309
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=92309&view=rev
>> Log:
>> Implement edit distance for StringRef
>
> Nice! Can this use SmallVector instead of vector, and get a unittest?

Done, thanks!

> - Daniel
>
>> Modified:
>>    llvm/trunk/include/llvm/ADT/StringRef.h
>>    llvm/trunk/lib/Support/StringRef.cpp
>>
>> Modified: llvm/trunk/include/llvm/ADT/StringRef.h
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/StringRef.h?rev=92309&r1=92308&r2=92309&view=diff
>>
>> === 
>> === 
>> === 
>> =====================================================================
>> --- llvm/trunk/include/llvm/ADT/StringRef.h (original)
>> +++ llvm/trunk/include/llvm/ADT/StringRef.h Wed Dec 30 11:23:44 2009
>> @@ -133,6 +133,22 @@
>>     /// 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); }
>>
>>
>> Modified: llvm/trunk/lib/Support/StringRef.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/StringRef.cpp?rev=92309&r1=92308&r2=92309&view=diff
>>
>> === 
>> === 
>> === 
>> =====================================================================
>> --- llvm/trunk/lib/Support/StringRef.cpp (original)
>> +++ llvm/trunk/lib/Support/StringRef.cpp Wed Dec 30 11:23:44 2009
>> @@ -8,6 +8,7 @@
>>  // 
>> === 
>> --- 
>> ------------------------------------------------------------------- 
>> ===//
>>
>>  #include "llvm/ADT/StringRef.h"
>> +#include <vector>
>>  using namespace llvm;
>>
>>  // MSVC emits references to this into the translation units which  
>> reference it.
>> @@ -35,6 +36,36 @@
>>   return Length < RHS.Length ? -1 : 1;
>>  }
>>
>> +/// \brief Compute the edit distance between the two given strings.
>> +unsigned StringRef::edit_distance(llvm::StringRef Other,
>> +                                  bool AllowReplacements) {
>> +  size_type m = size();
>> +  size_type n = Other.size();
>> +
>> +  std::vector<unsigned> previous(n+1, 0);
>> +  for (std::vector<unsigned>::size_type i = 0; i <= n; ++i)
>> +    previous[i] = i;
>> +
>> +  std::vector<unsigned> current(n+1, 0);
>> +  for (size_type y = 1; y <= m; ++y) {
>> +    current.assign(n+1, 0);
>> +    current[0] = y;
>> +    for (size_type x = 1; x <= n; ++x) {
>> +      if (AllowReplacements) {
>> +        current[x] = min(previous[x-1] + ((*this)[y-1] == Other 
>> [x-1]? 0u:1u),
>> +                         min(current[x-1], previous[x])+1);
>> +      }
>> +      else {
>> +        if ((*this)[y-1] == Other[x-1]) current[x] = previous[x-1];
>> +        else current[x] = min(current[x-1], previous[x]) + 1;
>> +      }
>> +    }
>> +    current.swap(previous);
>> +  }
>> +
>> +  return previous[n];
>> +}
>> +
>>  // 
>> === 
>> --- 
>> ------------------------------------------------------------------- 
>> ===//
>>  // String Searching
>>  // 
>> === 
>> --- 
>> ------------------------------------------------------------------- 
>> ===//
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>