[Numpy-discussion] hstack(arr_Int32, arr_float32) fails because of casting rules

[Travis Oliphant]

Sebastian Haase wrote:

>Hi,
>I get
>TypeError: array cannot be safely cast to required type
>
>when calling hstack()  ( which calls  concatenate() )
>on two arrays being a int32 and a float32 respectively.
>
>I understand now that a int32 cannot be safely converted into a float32
>but why does  concatenate  not automatically
>up(?) cast to float64  ??
>  
>
Basically, NumPy is following Numeric's behavior of raising an error in 
this case of unsafe casting in concatenate.  For functions that are not 
universal-function objects, mixed-type behavior works basically just 
like Numeric did (using the ordering of the types to determine which one 
to choose as the output).  

It could be argued that the ufunc-rules should be followed instead.

-Travis