Re: deriving from complex

[ajsiegel]

Schüle Daniel wrote:
 thank you
 I will have to take a closer look on __new__

 Regards, Daniel

The pypy implementation of the complex builtin may give you some
clues.

I found it helpful.

http://codespeak.net/svn/pypy/dist/pypy/lib/cmath.py

Art

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Re: deriving from complex

[ajsiegel]

Meant:

http://codespeak.net/svn/pypy/dist/pypy/module/__builtin__/app_complex.py

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Re: deriving from complex

[Schüle Daniel]

what do you think of this design?

  def polar(x,y=None):
... if type(x) in (list,tuple) and len(x) == 2 and y is None:
... return complex(x[0]*cos(x[1]), x[0]*sin(x[1]))
... if type(x) is complex and y is None:
... return (abs(x), atan2(x.imag,x.real))
... if type(x) in (float, int, long) and type(y) in (float, int, long):
... return complex(x*cos(y), x*sin(y))
...
  polar(2**0.5, 45.0/360*2*pi)
(1.0002+1j)
  polar((2**0.5, 45.0/360*2*pi))
(1.0002+1j)
  polar([2**0.5, 45.0/360*2*pi])
(1.0002+1j)
  polar(1+1j)
(1.4142135623730951, 0.78539816339744828)
 

btw I like how Ruby handles the creation of complex numbers

c = Complex(1,1)
p = Complex.polar(1,45.0/360*2*PI)

Regards, Daniel

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Re: deriving from complex

[Scott David Daniels]

Schüle Daniel wrote:
 I am trying to customize the handling of complex numbers
 what I am missing is a builtin possibility to create
 complex numbers in polar coordinates I wrote...:
   def polar(r,arg):
 ... re, im = r*cos(arg), r*sin(arg)
 ... return re + im*1j
 then I tried to extend this to a class
   class Complex(complex):
 ... def __init__(self,x,y,polar=False):
 ... if not polar:
 ... self.re, self.im = x,y
 ... else:
 ... self.re, self.im = x*cos(y), x*sin(y)

What you are missing is that complex is an immutable type.
You need to fiddle with __new__, not __init__.

 class Complex(complex):
 def __new__(class_, x, y=0.0, polar=False):
 if polar:
 return complex.__new__(class_, x * cos(y), x * sin(y))
 else:
 return complex.__new__(class_, x, y)

Which will produce instances of Complex, or:

 class Complex(complex):
 def __new__(class_, x, y=0.0, polar=False):
 if polar:
 return complex(x * cos(y), x * sin(y))
 else:
 return complex(class_, x, y)

Which will produce instances of complex.

--Scott David Daniels
[EMAIL PROTECTED]
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Re: deriving from complex

[Scott David Daniels]

Scott David Daniels wrote:
 Schüle Daniel wrote:
 ... 
And, of course, I reply with a cutto-pasto (pre-success code).
 ...
 Which will produce instances of Complex, or:
 class Complex(complex):
 def __new__(class_, x, y=0.0, polar=False):
 if polar:
 return complex(x * cos(y), x * sin(y))
 else:
 return complex(class_, x, y)
This last line should, of course, be:
   return complex(x, y)

--Scott David Daniels
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Re: deriving from complex

[Scott David Daniels]

Schüle Daniel wrote:
...
 btw I like how Ruby handles the creation of complex numbers
 
 c = Complex(1,1)
 p = Complex.polar(1,45.0/360*2*PI)

class Complex(complex):
 @classmethod
 def polar(class_, radius, angle):
 return class_(radius * cos(angle), radius * sin(angle))

--Scott David Daniels
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Re: deriving from complex

[Schüle Daniel]

thank you
I will have to take a closer look on __new__

Regards, Daniel

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