Re: [IMP-dev] Annoyance with current restraint design

[Ben Webb <>]

Daniel Russel wrote:
> I have some restraints which I want to have be semi-dynamic, meaning,  
> I want to be able to reset the list of particles which they act on.  
> This doesn't work so cleanly with restraints taking lists of  
> ParticleIndexes as then you need one version of set_particles to be  
> called from the constructor (where the Restraint::model_ is not set)  
> and another version to be called by outsiders after the model pointer  
> has been set (or pass the model pointer to both and ignore the stored  
> pointer).
>
> This seems like a reason for writing restraints which take Particles  
> rather than ParticleIndexes.

Agreed. As we already discussed, Particle* is easier to pass from Python 
than ParticleIndex anyway. The only downsides are that
1) There's no easy way to check for a 'bad' particle this way (a corrupt 
Particle could have a pointer to the model, but the model may not have 
the corresponding pointer to the Particle). With particle indexes of 
course you just check whether the index is in range.
2) This works only as long as the model's particle storage is 
std::vector<Particle*>. For example, we couldn't switch to 
std::vector<Particle> because then the Particle* could change when the 
vector is resized.
3) To be really careful, we should add checks that all particles live in 
the same model.

I don't think these are huge problems, however.

	Ben
--
                      http://salilab.org/~ben/
"It is a capital mistake to theorize before one has data."
	- Sir Arthur Conan Doyle