Merge pull request #125 from jvkersch/fix-tuple-indexing

Fix negative indexing issue.

src/runtime/tuple.cpp

@@ -70,11 +70,9 @@ Box* tupleGetitemInt(BoxedTuple* self, BoxedInt* slice) {
     i64 size = self->elts.size();
 
     if (n < 0)
-        n = size - n;
-    if (n < 0 || n >= size) {
-        fprintf(stderr, "IndexError: tuple index out of range\n");
-        raiseExcHelper(IndexError, "");
-    }
+        n = size + n;
+    if (n < 0 || n >= size)
+        raiseExcHelper(IndexError, "tuple index out of range");
 
     Box* rtn = self->elts[n];
     return rtn;

test/tests/tuples.py

@@ -153,3 +153,18 @@ try:
     t[(1, 2)]
 except TypeError as e:
     print e
+
+# Single element indexing.
+t = (1, None, "abc")
+for n in range(-3, 3):
+    print t[n]
+
+try:
+    t[-4]
+except IndexError as e:
+    print e
+
+try:
+    t[3]
+except IndexError as e:
+    print e