TODO: support for multidimensional arrays.

def _reduce_op(self, op, result=None):
        '''
        TODO: support for multidimensional arrays.
        '''
        template = 'result(for({arr},merger[{type}, {op}], |b, i, e| merge(b, e)))'
        self.weldobj.weld_code = template.format(arr = self.weldobj.weld_code,
                                                 type = self._weld_type.__str__(),
                                                 op  = op)
        return self._eval(restype = self._weld_type)