`real` and `imag` of `complex` should return `float`

[eviatarbach]

real(z) and imag(z), where z is complex, as of now returns a complex. It should return a float, since that makes it consistent with real(CC(3, 4)), for example. It also fixes problems with plotting the real or imaginary parts of complex functions.

[eviatarbach]

Patchbot apply trac15032.patch

[ppurka]

The new functions needs some doctests to check that the type is correct.

I am actually quite surprised by the inconsistency of the Sage implementation. self.real contains the number in the case of python's complex but it is a function in Sage's implementation. Do you know what is the reason behind the function in the Sage implementation?

sage: a = CC(1)     
sage: a.real
<function real>
sage: a = complex(1)
sage: a.real
1.0

EDIT Actually just shift the doctests to within the __call__ functions.

[eviatarbach]

Okay, I'll add the tests.

I think the reason for the functions is that it's converting from MPFR. It could be changed with the @property decorator so that self.real will work.

[eviatarbach]

I added the tests to __call__ but also left the other ones intact, since the __call__ ones aren't visible in the documentation.

[ppurka]

Looks good to me. All tests pass in sage/rings and sage/functions

Patchbot apply trac15032.3.patch