Steven D'Aprano wrote:
On Fri, 10 Mar 2006 02:19:10 +0100, Schüle Daniel wrote:
yeah, i miss some things in complex implementation
for example c=complex()
c.abs = 2**0.5
c.angle = pi/2
should result in 1+1j :)
Smiley noted, but consider:
c = complex()
= what is the value of c here?
default value is 0, for complex number that means
real = 0, imag = 0
is the same as
c.abs=0, c.angle=0
ok mathematically c.angle can be of arbitrary value
but defaulting it to zero is very handy
c = complex()
c.abs = 10
yields 10+0j
c=complex()
c.real = 2
c.imag = 2
c.abs = 50**0.5 # angle remains, length changed
yields 5+5j
c.angle = 0
yields 50**0.5 + 0j
c.abs = 2**0.5
= what is c's value now?
c.abs = 2**0.5
c.angle = 0
c.angle = pi/2
= now c has the value 1+1j
Objects with indeterminate values are rarely a good idea.
IMHO it's perfectly consistent with
int()
0
long()
0L
float()
0.0
complex()
complex()
0j
but extending complex with default angle=0
A better way would be for complex numbers to take a constructor that can
take arguments in either Cartesian or polar form. So, hypothetically, the
following would all be equivalent:
1+1j
complex(1,1)
complex(real=1, img=1)
complex(len=2**0.5, theta=pi/2)
ack
but after the creation of complex number one will have to
do all the transformations in another coord. system manually
Another alternative would be a function to construct polar form complex
numbers. It could be a plain function or a static method:
cmath.polar(2**0.5, pi/2) = 1+1j
complex.polar(2**0.5, pi/2) = 1+1j
maybe adding
c=complex.from_polar((length,angle))
d=complex.to_polar(c)
d == (length, angle)
True
would be sufficient, but I would prefer the other version
Regards
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