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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deriving from complex

[Schüle Daniel]

Hello

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

so first I wrote a standalone function

  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

  from math import *

  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)
...
 
  c=Complex(1,1)
  c
(1+1j)
  p=Complex(10,45.0/360*2*pi,True)
Traceback (most recent call last):
   File stdin, line 1, in ?
TypeError: complex() takes at most 2 arguments (3 given)
 

and got stuck with this error
it seems that last argument is rejected
because complex wants to have 2 arguments
but this works well ..

  class X(object):
... def __init__(self,a):
... self.a = a
...
  class Y(X):
... def __init__(self,a,b):
... self.a = a
... self.b = b
...
  y=Y(1,2)

what's causing the above exception?

one more question

  class Complex(complex):
... def __init__(self,x,y):
... self.real = x
... self.imag = y
...
  c=Complex(1,1)
Traceback (most recent call last):
   File stdin, line 1, in ?
   File stdin, line 3, in __init__
TypeError: readonly attribute
 

how can I work around this problem?

Regards, Daniel

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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
[EMAIL PROTECTED]
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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
[EMAIL PROTECTED]
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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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