Apologies:
a =: 0 { ]
b =: 1 { ]
c =: 2 { ]
roots =: ( (-@b) (+ , -) [: %: *:@b - 4 * a * c ) % 2 * a
roots 1 3 2
_1 _2
roots 1 0 1
0j1 0j_1
roots 1 2 1
_1 _1
Kip Murray
Sent from my iPad
On Dec 11, 2012, at 5:29 PM, Roger Hui <[email protected]> wrote:
> There are some cheeky (or is it cheesy?) versions:
>
> (2*a) %~ (-b) (+,-) %: (b^2) - 4*a*c NB. Kip Murray
> (2*a) %~ - b (+,-) %: (b^2) - 4*a*c
> (+:a) %~ - b (+,-) %: (*:b) - 4*a*c
> -: a %~ - b (+,-) %: (*:b) - 4*a*c
>
>
>
> On Tue, Dec 11, 2012 at 11:37 AM, km <[email protected]> wrote:
>
>> It appears this could be translated into J as the rather cool
>>
>> (2*a) %~ (-b) (+,-) %: (b^2) - 4*a*c
>>
>> Sent from my iPad
>>
>>
>> On Dec 11, 2012, at 12:59 PM, Roger Hui <[email protected]> wrote:
>>
>>> Example from the Iverson and McDonnell *Phrasal
>>> Forms*<http://www.jsoftware.com/papers/fork.htm>paper (which
>>> introduced fork):
>>>
>>> (-b)(+,-)√((b*2)-4×a×c)÷2×a
>>>
>>> √ is a postulated APL primitive, spelled %: in J.
>>>
>>>
>>>
>>>
>>> On Tue, Dec 11, 2012 at 10:49 AM, km <[email protected]> wrote:
>>>
>>>> What is the coolest way of programming the quadratic formula in J? We
>> are
>>>> finding the roots of polynomial c + x*(b + x*a) without using p. . I
>> offer
>>>>
>>>> roots
>>>> 3 : 0
>>>> 'a b c' =. y
>>>> q =. %: (b^2) - 4*a*c
>>>> (2*a) %~ (-b) + q,-q
>>>> )
>>>> roots 1 3 2
>>>> _1 _2
>>>> roots 1 0 1
>>>> 0j1 0j_1
>>>> roots 1 _2 1
>>>> 1 1
>>>>
>>>> partly as problem definition. I am looking for cool roots verbs!
>>>>
>>>> Kip Murray
>>>>
>>>> Sent from my iPad
>>>>
>>>> ----------------------------------------------------------------------
>>>> 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
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
