numpy · charris · Apr 1, 2013 · Feb 23, 2013 · Feb 26, 2013 · Mar 1, 2013
diff --git a/doc/release/1.8.0-notes.rst b/doc/release/1.8.0-notes.rst
@@ -37,6 +37,13 @@ compiler, then it's possible you will encounter problems. If so, please
 file a bug and as a temporary workaround you can re-enable the old build
 system by exporting the shell variable NPY_SEPARATE_COMPILATION=0.
 
+For the AdvancedNew iterator the ``oa_ndim`` flag should now be -1 to indicate
+that no ``op_axes`` and ``itershape`` are passed in. The ``oa_ndim == 0``
+case, now indicates a 0-D iteration and ``op_axes`` being NULL and the old 
+usage is deprecated. This does not effect the ``NpyIter_New`` or
+``NpyIter_MultiNew`` functions.
+
+
 New features
 ============
 

diff --git a/doc/source/reference/c-api.iterator.rst b/doc/source/reference/c-api.iterator.rst
@@ -634,12 +634,12 @@ Construction and Destruction
     Extends :cfunc:`NpyIter_MultiNew` with several advanced options providing
     more control over broadcasting and buffering.
 
-    If 0/NULL values are passed to ``oa_ndim``, ``op_axes``, ``itershape``,
+    If -1/NULL values are passed to ``oa_ndim``, ``op_axes``, ``itershape``,
     and ``buffersize``, it is equivalent to :cfunc:`NpyIter_MultiNew`.
 
-    The parameter ``oa_ndim``, when non-zero, specifies the number of
+    The parameter ``oa_ndim``, when not zero or -1, specifies the number of
     dimensions that will be iterated with customized broadcasting.
-    If it is provided, ``op_axes`` and/or ``itershape`` must also be provided.
+        If it is provided, ``op_axes`` must and ``itershape`` can also be provided.
     The ``op_axes`` parameter let you control in detail how the
     axes of the operand arrays get matched together and iterated.
     In ``op_axes``, you must provide an array of ``nop`` pointers
@@ -649,6 +649,11 @@ Construction and Destruction
     -1 which means ``newaxis``.  Within each ``op_axes[j]`` array, axes
     may not be repeated.  The following example is how normal broadcasting
     applies to a 3-D array, a 2-D array, a 1-D array and a scalar.
+
+    **Note**: Before NumPy 1.8 ``oa_ndim == 0` was used for signalling that
+    that ``op_axes`` and ``itershape`` are unused. This is deprecated and
+    should be replaced with -1. Better backward compatibility may be
+    achieved by using :cfunc:`NpyIter_MultiNew` for this case.
 
     .. code-block:: c
 

diff --git a/numpy/core/src/multiarray/nditer_api.c b/numpy/core/src/multiarray/nditer_api.c
@@ -134,12 +134,10 @@ NpyIter_RemoveAxis(NpyIter *iter, int axis)
     axisdata = NIT_INDEX_AXISDATA(axisdata_del, 1);
     memmove(axisdata_del, axisdata, (ndim-1-xdim)*sizeof_axisdata);
 
-    /* If there is more than one dimension, shrink the iterator */
-    if (ndim > 1) {
-        NIT_NDIM(iter) = ndim-1;
-    }
-    /* Otherwise convert it to a singleton dimension */
-    else {
+    /* Shrink the iterator */
+    NIT_NDIM(iter) = ndim - 1;
+    /* If it is now 0-d fill the singleton dimension */
+    if (ndim == 1) {
         npy_intp *strides = NAD_STRIDES(axisdata_del);
         NAD_SHAPE(axisdata_del) = 1;
         for (iop = 0; iop < nop; ++iop) {
@@ -642,6 +640,9 @@ NpyIter_GetIterIndex(NpyIter *iter)
         npy_intp sizeof_axisdata;
 
         iterindex = 0;
+        if (ndim == 0) {
+            return 0;
+        }
         sizeof_axisdata = NIT_AXISDATA_SIZEOF(itflags, ndim, nop);
         axisdata = NIT_INDEX_AXISDATA(NIT_AXISDATA(iter), ndim-1);
 
@@ -1750,6 +1751,8 @@ npyiter_goto_iterindex(NpyIter *iter, npy_intp iterindex)
 
     NIT_ITERINDEX(iter) = iterindex;
 
+    ndim = ndim ? ndim : 1;
+
     if (iterindex == 0) {
         dataptr = NIT_RESETDATAPTR(iter);