> On 02 Jan 2016, at 20:54, Dan Kogai (via RT) <perl6-bugs-follo...@perl.org> > wrote: > > # New Ticket Created by Dan Kogai > # Please include the string: [perl #127126] > # in the subject line of all future correspondence about this issue. > # <URL: https://rt.perl.org/Ticket/Display.html?id=127126 > > > > Oops, the previous message does not contain the patch so I am submitting > again. Use the patch below or just pull > https://github.com/rakudo/rakudo/pull/667 . > > ==== > > I am glad perl6 supports complex numbers natively. What I am not glad is that > its definition of i does not agree with mathematics: > > % perl6 > >> sqrt(-1+0i) > 6.12323399573677e-17+1i > > Though (-1+0i)**0.5 != 1i for most other platforms, they still get > sqrt(-1+0i) right: > > % python > > Python 2.7.10 (default, Oct 23 2015, 18:05:06) > [GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.0.59.5)] on darwin > Type "help", "copyright", "credits" or "license" for more information. >>>> from cmath import * >>>> sqrt(-1+0j) > 1j >>>> (-1+0j)**0.5 > (6.123233995736766e-17+1j) >>>> ^D > > % irb > > irb(main):001:0> require 'cmath' > => true > irb(main):002:0> CMath.sqrt(-1) > => (0+1.0i) > irb(main):003:0> ^D > > % perl -MMath::Complex -dE 1 > > Loading DB routines from perl5db.pl version 1.49 > Editor support available. > > Enter h or 'h h' for help, or 'man perldebug' for more help. > > main::(-e:1): 1 > DB<1> p sqrt(-1+0*i) > i > DB<2> p (-1+0*i)**0.5 > 6.12323399573677e-17+i > > So here is the patch that defines sqrt in sqrt. > > Dan the Complex Perl6 Newbie > > --- > src/core/Complex.pm | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/src/core/Complex.pm b/src/core/Complex.pm > index 8314025..74b1d5b 100644 > --- a/src/core/Complex.pm > +++ b/src/core/Complex.pm > @@ -80,8 +80,10 @@ my class Complex is Cool does Numeric { > } > > method sqrt(Complex:D:) { > - my Num ($mag, $angle) = self.polar; > - $mag.sqrt.unpolar($angle/2); > + my Num $abs = self.abs; > + my Num $re = (($abs + self.re)/2).sqrt; > + my Num $im = (($abs - self.re)/2).sqrt; > + Complex.new($re, self.im < 0 ?? -$im !! $im); > } > > multi method exp(Complex:D:) { > -- > 2.5.4 (Apple Git-61)
Pull request 667 has been merged, this ticket can be closed. Liz
