title: list index error with numba guvectorize
body: <p>I am new to numba / numbapro. I was trying to run one of the examples, this one about generalised Ufuncs with guvectorize:</p>
  
  <p>(Here the link to the example): <a href="http://docs.continuum.io/numbapro/quickstart.html#numbapro-guvectorize" rel="nofollow">http://docs.continuum.io/numbapro/quickstart.html#numbapro-guvectorize</a></p>
  
  <pre><code>import numbapro as numbapro
  
  @numbapro.guvectorize(['void(int32[:], int32[:])'], '(n)-&gt;()')
  def sum_row(inp, out):
      """
      Sum every row
  
      function type: two arrays
                     (note: scalar is represented as an array of length 1)
      signature: n elements to scalar
      """
      tmp = 0.
      for i in range(inp.shape[0]):
          tmp += inp[i]
      out[0] = tmp
  </code></pre>
  
  <p>I get this error:</p>
  
  <pre><code>IndexError                                Traceback (most recent call last)
  &lt;ipython-input-98-79514a184595&gt; in &lt;module&gt;()
  ----&gt; 1 @numbapro.guvectorize(['void(int32[:], int32[:])'], '(n)-&gt;()')
        2 def sum_row(inp, out):
        3     """
        4     Sum every row
        5 
  
  /users/adelacalle/anaconda_linux/lib/python2.7/site-packages/numba/npyufunc/decorators.pyc in wrap(func)
      117         for fty in ftylist:
      118             guvec.add(fty)
  --&gt; 119         return guvec.build_ufunc()
      120 
      121     return wrap
  
  /users/adelacalle/anaconda_linux/lib/python2.7/site-packages/numba/npyufunc/ufuncbuilder.pyc in build_ufunc(self)
      149 
      150         for sig, cres in self.nb_func.overloads.items():
  --&gt; 151             dtypenums, ptr = self.build(cres)
      152             dtypelist.append(dtypenums)
      153             ptrlist.append(utils.longint(ptr))
  
  /users/adelacalle/anaconda_linux/lib/python2.7/site-packages/numba/npyufunc/ufuncbuilder.pyc in build(self, cres)
      167         signature = cres.signature
      168         wrapper = build_gufunc_wrapper(ctx, cres.llvm_func, signature,
  --&gt; 169                                        self.sin, self.sout)
      170         ctx.engine.add_module(wrapper.module)
      171         ptr = ctx.engine.get_pointer_to_function(wrapper)
  
  /users/adelacalle/anaconda_linux/lib/python2.7/site-packages/numba/npyufunc/wrappers.pyc in build_gufunc_wrapper(context, func, signature, sin, sout)
      143     for i, (typ, sym) in enumerate(zip(signature.args, sin + sout)):
      144         ary = GUArrayArg(context, builder, arg_args, arg_dims, arg_steps, i,
  --&gt; 145                          step_offset, typ, sym, sym_dim)
      146         step_offset += ary.ndim
      147         arrays.append(ary)
  
  /users/adelacalle/anaconda_linux/lib/python2.7/site-packages/numba/npyufunc/wrappers.pyc in __init__(self, context, builder, args, dims, steps, i, step_offset, typ, syms, sym_dim)
      207         self.array = arycls(context, builder)
      208         self.array.data = builder.bitcast(self.data, self.array.data.type)
  --&gt; 209         self.array.shape = cgutils.pack_array(builder, self.shape)
      210         self.array.strides = cgutils.pack_array(builder, self.strides)
      211         self.array_value = self.array._getpointer()
  
  /users/adelacalle/anaconda_linux/lib/python2.7/site-packages/numba/cgutils.pyc in pack_array(builder, values)
      257 def pack_array(builder, values):
      258     n = len(values)
  --&gt; 259     ty = values[0].type
      260     ary = Constant.undef(Type.array(ty, n))
      261     for i, v in enumerate(values):
  
  IndexError: list index out of range
  </code></pre>
  
  <p>I do not found more documentation than this link. Am I doing something wrong? I found that this happens when there is an empty bracket in the signature. 
  I am running this on a linux machine, and my version of numbapro is 0.14.1</p>
  
  <p>Thanks in advance,</p>
  
  <p>Alex</p>