Is there a cool tacit way to program the quadratic formula in J? Maybe we should be happy with the cool explicit way given by Iverson and McDonnell. I have a more-or-less obvious tacit verb that begins by using A. to rearrange the argument vector a,b,c . Kip Murray
Sent from my iPad On Dec 11, 2012, at 1:37 PM, km <k...@math.uh.edu> 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 <rogerhui.can...@gmail.com> 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 <k...@math.uh.edu> 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
