Except that _1 is a valid index value in J. I have written a cover
for "iota" (in APL) that returned negative one for just the reason you
give.
On Mon, Apr 23, 2012 at 5:33 PM, Henry Rich <henryhr...@nc.rr.com> wrote:
> That convenience would also obtain (in J) if the 'not found' result were
> _1; and then the 'not found' entry would be known in advance and we
> wouldn't have to calculate it.
>
> Henry Rich
>
> On 4/23/2012 5:28 PM, Devon McCormick wrote:
>> The convenience of index returning one more than the maximum is that
>> it allows you to put your null (or other default) value at the end of
>> your lookup vector, e.g.
>>
>> (Target,a:){~Source getIndex Target
>> +-+---+-++
>> |a|bcd|e||
>> +-+---+-++
>>
>> or maybe you want
>>
>> (Source,a:){~Source i. Target
>> +-+-+---++
>> |e|a|bcd||
>> +-+-+---++
>>
>> The last item is an empty vector because it's not found and that's the
>> extra item we put at the end.
>>
>> On Mon, Apr 23, 2012 at 7:35 AM, Henry Rich<henryhr...@nc.rr.com> wrote:
>>> Source =. 'a';'bcd';'e';'g'
>>> Target =. 'e';'a';'bcd';'f'
>>> getIndex =: i.~ NB. not e.
>>> shouldReturn =. 1 2 0 4 NB. 'not found' for i. is #x
>>> assert (Source getIndex Target)-:shouldReturn NB. -: not =
>>>
>>> Henry Rich
>>>
>>> On 4/23/2012 7:13 AM, Joe Bohart wrote:
>>>> Hi J'ers,
>>>>
>>>> I'm trying to write a verb that will
>>>> match the items in Source with Target
>>>> and return the index of items in Target
>>>> such that they are in the same order as
>>>> Source with nulls (or the J way of handling nulls)
>>>> if no match is found.
>>>>
>>>> This is what i have (and it's wrong):
>>>>
>>>> Source =. 'a';'bcd';'e';'g'
>>>> Target =. 'e';'a';'bcd';'f'
>>>> getIndex =: e.
>>>> shouldReturn =. 1 2 0 null
>>>> assert (Source getIndex Target)=shouldReturn
>>>>
>>>> In the forums I've found solution candidates,but
>>>> haven't been able to apply them and am a bit lost with:
>>>> I.@:E. and ;:
>>>>
>>>> The concept of expressing null or missing data in J I haven't
>>>> found much info on. Where can i find more information on nulls.
>>>>
>>>> Much Thanks -Joe
>>>> ----------------------------------------------------------------------
>>>> For information about J forums see http://www.jsoftware.com/forums.htm
>>>>
>>> ----------------------------------------------------------------------
>>> For information about J forums see http://www.jsoftware.com/forums.htm
>>
>>
>>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
--
Devon McCormick, CFA
^me^ at acm.
org is my
preferred e-mail
----------------------------------------------------------------------
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