2 0 3&p. is a quadratic polynomial with two roots. The multivalued inverse won't work as a j obverse. The wikipedia "square root" entry justifies the j definition of %: which returns 1 value, "Although the principal square root of a positive number is only one of its two square roots, the designation "the square root" is often used to refer to the principal square root."
square =: 0 0 1&p. (*: -: square) ((%~ i.) , ?~)8 1 square b. _1 NB. just right |domain error | square b._1 *: b. _1 NB. just right %: %: *: _1 NB. obverse is not inverse 1 > From: "Linda Alvord" <[email protected]> > To: <[email protected]> > Subject: Re: [Jprogramming] Basic Mystery > Message-ID: <000701ce0907$458e0740$d0aa15c0$@net> > Content-Type: text/plain; charset=US-ASCII > > Although g and h both produce y correctly, h can't be used > with b. > and ^:_1 > > g=: 2+3**: > ]y=: g 5 > 77 > h=: 13 : '2 0 3 p. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
