I just noticed a typo in the formula repeated from the original paper. One of the left parens is misplaced:
(-b)(+,-)√((b*2)-4×a×c)÷2×a ⍝ wrong ((-b)(+,-)√(b*2)-4×a×c)÷2×a On Tue, Dec 11, 2012 at 10:59 AM, 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
