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Document the edit-distance algorithm used in StringRef, switch it over

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to SmallVector, and add a unit test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92340 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Douglas Gregor 2009-12-31 04:24:34 +00:00
parent 210d0febc2
commit 7e54d5b156
2 changed files with 19 additions and 5 deletions
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19
lib/Support/StringRef.cpp
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@ -8,7 +8,7 @@
//===----------------------------------------------------------------------===//
#include "llvm/ADT/StringRef.h"
#include <vector>
#include "llvm/ADT/SmallVector.h"
using namespace llvm;
// MSVC emits references to this into the translation units which reference it.
@ -36,17 +36,26 @@ int StringRef::compare_lower(StringRef RHS) const {
return Length < RHS.Length ? -1 : 1;
}
/// \brief Compute the edit distance between the two given strings.
// Compute the edit distance between the two given strings.
unsigned StringRef::edit_distance(llvm::StringRef Other,
bool AllowReplacements) {
// The algorithm implemented below is the "classic"
// dynamic-programming algorithm for computing the Levenshtein
// distance, which is described here:
//
// http://en.wikipedia.org/wiki/Levenshtein_distance
//
// Although the algorithm is typically described using an m x n
// array, only two rows are used at a time, so this implemenation
// just keeps two separate vectors for those two rows.
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)
SmallVector<unsigned, 32> previous(n+1, 0);
for (SmallVector<unsigned, 32>::size_type i = 0; i <= n; ++i)
previous[i] = i;
std::vector<unsigned> current(n+1, 0);
SmallVector<unsigned, 32> current(n+1, 0);
for (size_type y = 1; y <= m; ++y) {
current.assign(n+1, 0);
current[0] = y;

5
unittests/ADT/StringRefTest.cpp
View File

@ -247,6 +247,11 @@ TEST(StringRefTest, Count) {
EXPECT_EQ(0U, Str.count("zz"));
}
TEST(StringRefTest, EditDistance) {
StringRef Str("hello");
EXPECT_EQ(2, Str.edit_distance("hill"));
}
TEST(StringRefTest, Misc) {
std::string Storage;
raw_string_ostream OS(Storage);