[Numpy-discussion] arange(-10)

Todd Miller jmiller at stsci.edu
Tue Oct 8 05:07:04 CDT 2002


Pearu Peterson wrote:

>
>On Mon, 7 Oct 2002, Todd Miller wrote:
>
>>Pearu Peterson wrote:
>>
>>>On Mon, 7 Oct 2002, Todd Miller wrote:
>>>
>>>>The subject line contains what I consider to be an invalid range
>>>>expression.   Numarray, now and always, reacts badly to it.  Currently,
>>>>numarray tries to allocate a multi-gigabyte array.   In the past, it has
>>>>dumped core.
>>>>
>>>>The question is, what should it do?
>>>>
>>>>1. raise ValueError, "Invalid negative range expression"     (my +1)
>>>>2. zeros((0,), 'l')
>>>>                 (Numeric does this)
>>>>
>>>>Is there a good justification to keep the existing Numeric behavior?
>>>>Any other suggestions?
>>>>
>>>Does Numarray support empty arrays? If yes, I'd vote for Python behavior:
>>>
>>Numarray has no problem with empty arrays so both choices are easy to
>>implement.  It apparently has a different repr (than Numeric) for
>>"nothing" which is:
>>
>>array([])
>>
>
>Hmm, so it means that Numeric.arange is consistent with Python range after
>all.  Then I'd like to change my vote from exception to array([]) (if it
>is not too late).
>
>Rationale: sometimes using
>
>  range(i1) + range(i2) + range(i3)
>
>can save lots of code if the indices i1,i2,i3 can also be negative with
>the meaning that the resulting lists are then empty. If using arange, then
>the above would be equivalent to
>
>  concatenate((arange(i1),arange(i2),arange(i3)))
>
>or
>
>  concatenate(map(arange,[i1,i2,i3]))
>
>for short. Now, if arange would raise an exception if one of i1,i2,i3 is
>negative, then the above would not work without checking i1,i2,i3 first.
>And I find that bad because additional (read: meaningless) code is
>needed.
>
>Pearu
>
>
Hi Pearu,

Well, as fate would have it, your vote was already mis-cast in favor of 
Numeric compatability.  However, you've changed my mind, so I'm changing 
*my* vote.  That leaves the current vote at +2 "raise", +3 "compatible", 
so barring any new votes,  I'll check it in as Numeric compatible 
(returning an empty range) at COB today.

Todd

-- 
Todd Miller 			jmiller at stsci.edu
STSCI / SSB







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