Add optional startIndex to String.replaceFirst

runtime/lib/string_patch.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 patch class String {
   /* patch */ factory String.fromCharCodes(Iterable<int> charCodes) {
     return _StringBase.createFromCharCodes(charCodes);
   }
 
   /* patch */ factory String.fromCharCode(int charCode) {
@@ skipping 396 matching lines @@
   bool contains(Pattern pattern, [int startIndex = 0]) {
     if (pattern is String) {
       if (startIndex < 0 || startIndex > this.length) {
         throw new RangeError.range(startIndex, 0, this.length);
       }
       return indexOf(pattern, startIndex) >= 0;
     }
     return pattern.allMatches(this.substring(startIndex)).isNotEmpty;
   }
 
-  String replaceFirst(Pattern pattern, String replacement) {
+  String replaceFirst(Pattern pattern,
+                      String replacement,
+                      [int startIndex = 0]) {
     if (pattern is! Pattern) {
       throw new ArgumentError("${pattern} is not a Pattern");
     }
     if (replacement is! String) {
       throw new ArgumentError("${replacement} is not a String");
     }
-    StringBuffer buffer = new StringBuffer();
-    int startIndex = 0;
-    Iterator iterator = pattern.allMatches(this).iterator;
-    if (iterator.moveNext()) {
-      Match match = iterator.current;
-      buffer..write(this.substring(startIndex, match.start))
-            ..write(replacement);
-      startIndex = match.end;
+    if (startIndex is! int) {
+      throw new ArgumentError("${startIndex} is not an int");
     }
-    return (buffer..write(this.substring(startIndex))).toString();
+    if ((startIndex < 0) || (startIndex > this.length)) {
+      throw new RangeError.range(startIndex, 0, this.length);
+    }
+    Iterator iterator =
+      startIndex == 0 ? pattern.allMatches(this).iterator

[Lasse Reichstein Nielsen, 2014/08/19 07:26:45]

Indent by four.

[srawlins, 2014/08/19 21:42:32]

Done.

+                      : pattern.allMatches(this, startIndex).iterator;
+    if (!iterator.moveNext()) return this;
+    Match match = iterator.current;
+    return "${this.substring(0, match.start)}"
+           "$replacement"
+           "${this.substring(match.end)}";
   }
 
   String replaceAll(Pattern pattern, String replacement) {
     if (pattern is! Pattern) {
       throw new ArgumentError("${pattern} is not a Pattern");
     }
     if (replacement is! String) {
       throw new ArgumentError(
           "${replacement} is not a String or Match->String function");
     }
@@ skipping 560 matching lines @@
 class _CodeUnits extends Object with ListMixin<int>,
                                      UnmodifiableListMixin<int> {
   /** The string that this is the code units of. */
   String _string;
 
   _CodeUnits(this._string);
 
   int get length => _string.length;
   int operator[](int i) => _string.codeUnitAt(i);
 }