cpython/Demo/classes/Complex.py

# Complex numbers
# ---------------

# [Now that Python has a complex data type built-in, this is not very
# useful, but it's still a nice example class]

# This module represents complex numbers as instances of the class Complex.
# A Complex instance z has two data attribues, z.re (the real part) and z.im
# (the imaginary part).  In fact, z.re and z.im can have any value -- all
# arithmetic operators work regardless of the type of z.re and z.im (as long
# as they support numerical operations).
#
# The following functions exist (Complex is actually a class):
# Complex([re [,im]) -> creates a complex number from a real and an imaginary part
# IsComplex(z) -> true iff z is a complex number (== has .re and .im attributes)
# ToComplex(z) -> a complex number equal to z; z itself if IsComplex(z) is true
#                 if z is a tuple(re, im) it will also be converted
# PolarToComplex([r [,phi [,fullcircle]]]) ->
#	the complex number z for which r == z.radius() and phi == z.angle(fullcircle)
#	(r and phi default to 0)
# exp(z) -> returns the complex exponential of z. Equivalent to pow(math.e,z).
#
# Complex numbers have the following methods:
# z.abs() -> absolute value of z
# z.radius() == z.abs()
# z.angle([fullcircle]) -> angle from positive X axis; fullcircle gives units
# z.phi([fullcircle]) == z.angle(fullcircle)
#
# These standard functions and unary operators accept complex arguments:
# abs(z)
# -z
# +z
# not z
# repr(z) == `z`
# str(z)
# hash(z) -> a combination of hash(z.re) and hash(z.im) such that if z.im is zero
#            the result equals hash(z.re)
# Note that hex(z) and oct(z) are not defined.
#
# These conversions accept complex arguments only if their imaginary part is zero:
# int(z)
# long(z)
# float(z)
#
# The following operators accept two complex numbers, or one complex number
# and one real number (int, long or float):
# z1 + z2
# z1 - z2
# z1 * z2
# z1 / z2
# pow(z1, z2)
# cmp(z1, z2)
# Note that z1 % z2 and divmod(z1, z2) are not defined,
# nor are shift and mask operations.
#
# The standard module math does not support complex numbers.
# (I suppose it would be easy to implement a cmath module.)
#
# Idea:
# add a class Polar(r, phi) and mixed-mode arithmetic which
# chooses the most appropriate type for the result:
# Complex for +,-,cmp
# Polar   for *,/,pow


import types, math

twopi = math.pi*2.0
halfpi = math.pi/2.0

def IsComplex(obj):
	return hasattr(obj, 're') and hasattr(obj, 'im')

def ToComplex(obj):
	if IsComplex(obj):
		return obj
	elif type(obj) == types.TupleType:
		return apply(Complex, obj)
	else:
		return Complex(obj)

def PolarToComplex(r = 0, phi = 0, fullcircle = twopi):
	phi = phi * (twopi / fullcircle)
	return Complex(math.cos(phi)*r, math.sin(phi)*r)

def Re(obj):
	if IsComplex(obj):
		return obj.re
	else:
		return obj

def Im(obj):
	if IsComplex(obj):
		return obj.im
	else:
		return obj

class Complex:

	def __init__(self, re=0, im=0):
		if IsComplex(re):
			im = i + Complex(0, re.im)
			re = re.re
		if IsComplex(im):
			re = re - im.im
			im = im.re
		self.__dict__['re'] = re
		self.__dict__['im'] = im
	
	def __setattr__(self, name, value):
			raise TypeError, 'Complex numbers are immutable'

	def __hash__(self):
		if not self.im: return hash(self.re)
		mod = sys.maxint + 1L
		return int((hash(self.re) + 2L*hash(self.im) + mod) % (2L*mod) - mod)

	def __repr__(self):
		if not self.im:
			return 'Complex(%s)' % `self.re`
		else:
			return 'Complex(%s, %s)' % (`self.re`, `self.im`)

	def __str__(self):
		if not self.im:
			return `self.re`
		else:
			return 'Complex(%s, %s)' % (`self.re`, `self.im`)

	def __neg__(self):
		return Complex(-self.re, -self.im)

	def __pos__(self):
		return self

	def __abs__(self):
		# XXX could be done differently to avoid overflow!
		return math.sqrt(self.re*self.re + self.im*self.im)

	def __int__(self):
		if self.im:
			raise ValueError, "can't convert Complex with nonzero im to int"
		return int(self.re)

	def __long__(self):
		if self.im:
			raise ValueError, "can't convert Complex with nonzero im to long"
		return long(self.re)

	def __float__(self):
		if self.im:
			raise ValueError, "can't convert Complex with nonzero im to float"
		return float(self.re)

	def __cmp__(self, other):
		other = ToComplex(other)
		return cmp((self.re, self.im), (other.re, other.im))

	def __rcmp__(self, other):
		other = ToComplex(other)
		return cmp(other, self)
	
	def __nonzero__(self):
		return not (self.re == self.im == 0)

	abs = radius = __abs__

	def angle(self, fullcircle = twopi):
		return (fullcircle/twopi) * ((halfpi - math.atan2(self.re, self.im)) % twopi)

	phi = angle

	def __add__(self, other):
		other = ToComplex(other)
		return Complex(self.re + other.re, self.im + other.im)

	__radd__ = __add__

	def __sub__(self, other):
		other = ToComplex(other)
		return Complex(self.re - other.re, self.im - other.im)

	def __rsub__(self, other):
		other = ToComplex(other)
		return other - self

	def __mul__(self, other):
		other = ToComplex(other)
		return Complex(self.re*other.re - self.im*other.im,
		               self.re*other.im + self.im*other.re)

	__rmul__ = __mul__

	def __div__(self, other):
		other = ToComplex(other)
		d = float(other.re*other.re + other.im*other.im)
		if not d: raise ZeroDivisionError, 'Complex division'
		return Complex((self.re*other.re + self.im*other.im) / d,
		               (self.im*other.re - self.re*other.im) / d)

	def __rdiv__(self, other):
		other = ToComplex(other)
		return other / self

	def __pow__(self, n, z=None):
		if z is not None:
			raise TypeError, 'Complex does not support ternary pow()'
		if IsComplex(n):
			if n.im: 
			  if self.im: raise TypeError, 'Complex to the Complex power'
			  else: return exp(math.log(self.re)*n)
			n = n.re
		r = pow(self.abs(), n)
		phi = n*self.angle()
		return Complex(math.cos(phi)*r, math.sin(phi)*r)
	
	def __rpow__(self, base):
		base = ToComplex(base)
		return pow(base, self)
		
def exp(z):
	r = math.exp(z.re)
	return Complex(math.cos(z.im)*r,math.sin(z.im)*r)


def checkop(expr, a, b, value, fuzz = 1e-6):
	import sys
	print '       ', a, 'and', b,
	try:
		result = eval(expr)
	except:
		result = sys.exc_type
	print '->', result
	if (type(result) == type('') or type(value) == type('')):
		ok = result == value
	else:
		ok = abs(result - value) <= fuzz
	if not ok:
		print '!!\t!!\t!! should be', value, 'diff', abs(result - value)


def test():
	testsuite = {
		'a+b': [
			(1, 10, 11),
			(1, Complex(0,10), Complex(1,10)),
			(Complex(0,10), 1, Complex(1,10)),
			(Complex(0,10), Complex(1), Complex(1,10)),
			(Complex(1), Complex(0,10), Complex(1,10)),
		],
		'a-b': [
			(1, 10, -9),
			(1, Complex(0,10), Complex(1,-10)),
			(Complex(0,10), 1, Complex(-1,10)),
			(Complex(0,10), Complex(1), Complex(-1,10)),
			(Complex(1), Complex(0,10), Complex(1,-10)),
		],
		'a*b': [
			(1, 10, 10),
			(1, Complex(0,10), Complex(0, 10)),
			(Complex(0,10), 1, Complex(0,10)),
			(Complex(0,10), Complex(1), Complex(0,10)),
			(Complex(1), Complex(0,10), Complex(0,10)),
		],
		'a/b': [
			(1., 10, 0.1),
			(1, Complex(0,10), Complex(0, -0.1)),
			(Complex(0, 10), 1, Complex(0, 10)),
			(Complex(0, 10), Complex(1), Complex(0, 10)),
			(Complex(1), Complex(0,10), Complex(0, -0.1)),
		],
		'pow(a,b)': [
			(1, 10, 1),
			(1, Complex(0,10), 1),
			(Complex(0,10), 1, Complex(0,10)),
			(Complex(0,10), Complex(1), Complex(0,10)),
			(Complex(1), Complex(0,10), 1),
			(2, Complex(4,0), 16),
		],
		'cmp(a,b)': [
			(1, 10, -1),
			(1, Complex(0,10), 1),
			(Complex(0,10), 1, -1),
			(Complex(0,10), Complex(1), -1),
			(Complex(1), Complex(0,10), 1),
		],
	}
	exprs = testsuite.keys()
	exprs.sort()
	for expr in exprs:
		print expr + ':'
		t = (expr,)
		for item in testsuite[expr]:
			apply(checkop, t+item)
	

if __name__ == '__main__':
	test()