Le mardi 20 septembre 2016 04:02:16 UTC+2, Bill Page a écrit : > > In keeping with Richard's suggestion, in Sage I think a good > _algebraic_ definition of 'real' is > > bool(x/2+conjugate(x)/2 == x) >
why not bool(SR(x).imag_part()==0) ? > > So > > sage: def RN(x): > ....: try: > ....: return bool(x/2+conjugate(x)/2 == x) > ....: except: > ....: return false > > which also works whenever conjugate is defined, including > > sage: assume(x,'real') > sage: assume(y,'real') > sage: RN(sqrt(x^2+y^2)) > True > > > > On 19 September 2016 at 19:51, rjf <fat...@gmail.com <javascript:>> > wrote: > > If arg(x) is 0 and x is a number, then it is a real number. Maxima > calls > > this carg() for complex arg. > > > > Carg will also work for some things that are not of numeric type, but > > symbolic in some way. > > . > > Like sqrt(x^2+y^2) is real if domain=real > > > > Good luck > > > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
