use [].min

did not perform as well in older rubies?

Author: tcrouch

lib/edits/damerau_levenshtein.rb

@@ -67,14 +67,14 @@ def self.distance(seq1, seq2)
 
           # TODO: do insertion/deletion need to be considered when
           # seq1_item == seq2_item ?
-          deletion = matrix[row][col + 1] + 1
-          insertion = matrix[row + 1][col] + 1
-          substitution = matrix[row][col] + sub_cost
-
-          # step cost is min of operation costs
-          cost = substitution < insertion ? substitution : insertion
-          cost = deletion if deletion < cost
-          cost = transposition if transposition < cost
+          #
+          # substitution, deletion, insertion, transposition
+          cost = [
+            matrix[row][col] + sub_cost,
+            matrix[row][col + 1] + 1,
+            matrix[row + 1][col] + 1,
+            transposition
+          ].min
 
           matrix[row + 1][col + 1] = cost
 

lib/edits/levenshtein.rb

@@ -37,24 +37,25 @@ def self.distance(seq1, seq2)
       last_row = 0.upto(cols).to_a
 
       rows.times do |row|
-        last_col = row + 1
-
+        prev_col_cost = row + 1
         seq1_item = seq1[row]
 
         cols.times do |col|
-          deletion = last_row[col + 1] + 1
-          insertion = last_col + 1
-          substitution = last_row[col] + (seq1_item == seq2[col] ? 0 : 1)
-
+          # | Xs | Xd |
+          # | Xi | ?  |
           # step cost is min of operation costs
-          cost = deletion < insertion ? deletion : insertion
-          cost = substitution if substitution < cost
+          # substitution, deletion, insertion
+          cost = [
+            last_row[col] + (seq1_item == seq2[col] ? 0 : 1),
+            last_row[col + 1] + 1,
+            prev_col_cost + 1
+          ].min
 
           # overwrite previous row as we progress
-          last_row[col] = last_col
-          last_col = cost
+          last_row[col] = prev_col_cost
+          prev_col_cost = cost
         end
-        last_row[cols] = last_col
+        last_row[cols] = prev_col_cost
       end
 
       last_row[cols]

lib/edits/restricted_edit.rb

@@ -51,22 +51,25 @@ def self.distance(seq1, seq2)
         curr_row, last_row, lastlast_row = lastlast_row, curr_row, last_row
 
         curr_row[0] = row + 1
-        curr_item = seq1[row]
+        seq1_item = seq1[row]
 
         cols.times do |col|
-          sub_cost = curr_item == seq2[col] ? 0 : 1
-          is_swap = sub_cost == 1 &&
+          sub_cost = seq1_item == seq2[col] ? 0 : 1
+          is_swap = sub_cost.positive? &&
             row.positive? && col.positive? &&
-            curr_item == seq2[col - 1] &&
+            seq1_item == seq2[col - 1] &&
             seq1[row - 1] == seq2[col]
 
-          deletion = last_row[col + 1] + 1
-          insertion = curr_row[col] + 1
-          substitution = last_row[col] + sub_cost
-
+          # | Xt |    |    |
+          # |    | Xs | Xd |
+          # |    | Xi | ?  |
           # step cost is min of operation costs
-          cost = deletion < insertion ? deletion : insertion
-          cost = substitution if substitution < cost
+          # substitution, deletion, insertion, transposition
+          cost = [
+            last_row[col] + sub_cost,
+            last_row[col + 1] + 1,
+            curr_row[col] + 1
+          ].min
 
           if is_swap
             swap = lastlast_row[col - 1] + 1