KT-968 String should provide an iterator() method

compiler/tests/org/jetbrains/jet/codegen/StdlibTest.java

@@ -110,6 +110,23 @@ public class StdlibTest extends CodegenTestCase {
         } catch (Throwable t) {
 //            System.out.println(generateToText());
             t.printStackTrace();
+            throw t instanceof Exception ? (Exception)t : new RuntimeException(t);
+        }
+    }
+
+    public void testForInString() throws Exception {
+        loadText("fun foo() : Int {        var sum = 0\n" +
+                 "        for(c in \"239\")\n" +
+                 "            sum += (c.int - '0'.int)\n" +
+                 "        return sum" +
+                 "}" );
+        final Method main = generateFunction();
+        try {
+            assertEquals(14, main.invoke(null));
+        } catch (Throwable t) {
+            System.out.println(generateToText());
+            t.printStackTrace();
+            throw t instanceof Exception ? (Exception)t : new RuntimeException(t);
         }
     }
 }

stdlib/ktSrc/String.kt

@@ -66,3 +66,19 @@ inline fun String(stringBuffer : java.lang.StringBuffer) = java.lang.String(stri
 
 inline fun String(stringBuilder : java.lang.StringBuilder) = java.lang.String(stringBuilder) as String
 
+/*
+Iterator for characters of given String
+*/
+inline fun String.iterator() : CharIterator = (this as java.lang.String).iterator()
+
+/*
+Iterator for characters of given CharSequence
+*/
+inline fun java.lang.CharSequence.iterator() : CharIterator = object: jet.CharIterator() {
+    private var index = 0
+
+    public override fun nextChar(): Char = charAt(index++)
+
+    public override val hasNext: Boolean
+        get() = index < length()
+}

testlib/test/StringTest.kt

@@ -0,0 +1,28 @@
+package testString
+
+import std.io.*
+import stdhack.test.*
+
+import junit.framework.*
+
+class StringTest() : TestCase() {
+    fun testStringIterator() {
+        var sum = 0
+        for(c in "239")
+            sum += (c.int - '0'.int)
+        assertTrue(sum == 14)
+    }
+
+    fun testStringBuilderIterator() {
+        var sum = 0
+        val sb = StringBuilder()
+        for(c in "239")
+            sb.append(c)
+
+        println(sb)
+
+        for(c in sb)
+            sum += (c.int - '0'.int)
+        assertTrue(sum == 14)
+    }
+}