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

Travis Oliphant oliphant at ee.byu.edu
Thu Aug 24 19:28:19 CDT 2006

Sebastian Haase wrote:

>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.


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