[with patch, positive review] Adds __nonzero__ method to abelian groups

[tsutton]

 sage: E=EllipticCurve([0,82])
 sage: tor=E.torsion_subgroup()
 sage: if tor:
 ...       print tor.order()
 1

We'd like to have tor evaluate to false in boolean context.

[roed]

Needs a doctest.

[roed]

Looks good. All tests pass for me.

[ylchapuy]

Still needs a doctest!

[roed]

Now includes #indirect doctest

[mvngu]

What's the real name of tsutton? The real name should be used so we can give proper credit to contributors.

[mvngu]

I assume that I only need to apply the patch trac_6510.3.patch. But why are there three functions __nonzero__(self) all of which are the same and reside in the same module, but each block of definition contains different stuff? For example, after applying trac_6510.3.patch, I get the following in sage/groups/abelian_gps/abelian_group.py:

    def __nonzero__(self):
        return len(self.invariants()) != 0

    def __nonzero__(self):
        """                                                                     
        Returns True if this group is nontrivial.                               
                                                                                
        EXAMPLES::                                                              
                                                                                
            sage: E = EllipticCurve([0,82])                                     
            sage: T = E.torsion_subgroup()                                      
            sage: bool(T)                                                       
            False                                                               
        """
        return len(self.invariants()) != 0

    def __nonzero__(self):
        """                                                                     
        Returns True if this group is nontrivial.                               
                                                                                
        EXAMPLES::                                                              
                                                                                
            sage: E = EllipticCurve([0,82])                                     
            sage: T = E.torsion_subgroup()                                      
            sage: bool(T) # indirect doctest                                    
            False                                                               
        """
        return len(self.invariants()) != 0

Choose which block of function definition you want, and upload a new patch. Preferrably, you should replace trac_6510.3.patch with your new patch. I'm marking this as needs work. After a new patch is uploaded, positive review can be reinstated.

[roed]

Fixed. tsutton's real name is Taylor Sutton.

[mvngu]

Merged the patch trac_6510.3.patch in sage-4.1.1-alpha0. I can't close this ticket because I don't have the privilege to do so. Sorry, folks :-(