[perl #127125] Decent sqrt() - makes sqrt(-1+0i) == i

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# New Ticket Created by  Dan Kogai 
# Please include the string:  [perl #127125]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=127125 >


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