BUG: make empty inputs to ix_ create an empty int typed output

Fixes #5804

1 files changed, 7 insertions, 9 deletions

diff --git a/numpy/lib/index_tricks.py b/numpy/lib/index_tricks.py
index e97338106..2bb11bf1e 100644
--- a/numpy/lib/index_tricks.py
+++ b/numpy/lib/index_tricks.py
@@ -7,7 +7,7 @@ import numpy.core.numeric as _nx
 from numpy.core.numeric import (
     asarray, ScalarType, array, alltrue, cumprod, arange
     )
-from numpy.core.numerictypes import find_common_type
+from numpy.core.numerictypes import find_common_type, issubdtype
 
 from . import function_base
 import numpy.matrixlib as matrix
@@ -71,17 +71,15 @@ def ix_(*args):
     """
     out = []
     nd = len(args)
-    baseshape = [1]*nd
-    for k in range(nd):
-        new = _nx.asarray(args[k])
+    for k, new in enumerate(args):
+        # Explicitly type empty sequences to avoid float default
+        new = asarray(new, dtype=None if new else _nx.intp)
         if (new.ndim != 1):
             raise ValueError("Cross index must be 1 dimensional")
-        if issubclass(new.dtype.type, _nx.bool_):
-            new = new.nonzero()[0]
-        baseshape[k] = len(new)
-        new = new.reshape(tuple(baseshape))
+        if issubdtype(new.dtype, _nx.bool_):
+            new, = new.nonzero()
+        new.shape = (1,)*k + (new.size,) + (1,)*(nd-k-1)
         out.append(new)
-        baseshape[k] = 1
     return tuple(out)
 
 class nd_grid(object):