Also compact objects with not all identical values.

lib/jison.js

@@ -1173,17 +1173,33 @@ lrGeneratorMixin.generateTableCode = function (table) {
   // Don't surround numerical property name numbers in quotes
   moduleCode = moduleCode.replace(/"([0-9]+)"(?=:)/g, "$1");
 
-  // Replace objects with identical values for all keys by function calls
-  // e.g., { 1: [6,7]; 3: [6,7], 4: [6,7] } = o([6,7], [1, 3, 4])
-  moduleCode = moduleCode.replace(/\{\d+:(\[[^\]]+\]),\d+:\1[^\}]*\}/g, function (object, value) {
-    // Check if all values in this object are identical, and collect its keys
-    var keyValue, keys = [], keyValueMatcher = /(\d+):([^:]+)(?=,\d+:|\})/g;
-    while (keyValue = keyValueMatcher.exec(object))
-      // Only continue if the keys are identical
-      if (value !== keyValue[2]) return object;
-      else keys.push(keyValue[1])
-    // Create a function call with the value and all keys
-    return 'o(' + value + ',[' + keys.join(',') + '])';
+  // Replace objects with several identical values by function calls
+  // e.g., { 1: [6, 7]; 3: [6, 7], 4: [6, 7], 5: 8 } = o([1, 3, 4], [6, 7], { 5: 8 })
+  moduleCode = moduleCode.replace(/\{\d+:[^\}]+,\d+:[^\}]+\}/g, function (object) {
+    // Find the value that occurs with the highest number of keys
+    var value, frequentValue, key, keys = {}, keyCount, maxKeyCount = 0,
+        keyValue, keyValues = [], keyValueMatcher = /(\d+):([^:]+)(?=,\d+:|\})/g;
+    while ((keyValue = keyValueMatcher.exec(object))) {
+      // For each value, store the keys where that value occurs
+      key = keyValue[1], value = keyValue[2], keyCount = 1;
+      if (!(value in keys)) keys[value] = [key];
+      else keyCount = keys[value].push(key);
+      // Remember this value if it is the most frequent one
+      if (keyCount > maxKeyCount)
+        maxKeyCount = keyCount, frequentValue = value;
+    }
+    // Construct the object with a function call if the most frequent value occurs multiple times
+    if (maxKeyCount > 1) {
+      // Collect all non-frequent values into a remainder object
+      for (value in keys)
+        if (value !== frequentValue)
+          for (k = keys[value], i = 0, l = k.length; i < l; i++)
+            keyValues.push(k[i] + ':' + value);
+      keyValues = keyValues.length ? ',{' + keyValues.join(',') + '}' : '';
+      // Create the function call `o(keys, value, remainder)`
+      object = 'o([' + keys[frequentValue].join(',') + '],' + frequentValue + keyValues + ')';
+    }
+    return object;
   });
 
   // Count occurrences of number lists
@@ -1214,11 +1230,11 @@ lrGeneratorMixin.generateTableCode = function (table) {
     moduleCode: moduleCode
   };
 };
-// Function that creates an object with the given value for all given keys
-// e.g., o([6,7], [1, 3, 4]) = { 1: [6,7]; 3: [6,7], 4: [6,7] }
-var createObjectCode = 'o=function(v,a,l,r){' +
-  'for(l=a.length,r={};l--;r[a[l]]=v);' +
-  'return r}';
+// Function that extends an object with the given value for all given keys
+// e.g., o([1, 3, 4], [6, 7], { x: 1, y: 2 }) = { 1: [6, 7]; 3: [6, 7], 4: [6, 7], x: 1, y: 2 }
+var createObjectCode = 'o=function(k,v,o,l){' +
+  'for(o=o||{},l=k.length;l--;o[k[l]]=v);' +
+  'return o}';
 
 // Creates a variable with a unique name
 function createVariable() {