refactoring + add getters and setters

[ocots]

I have made some modifications. I have added getters for a solution but I have also renamed getters for a model. It is clearer for me with the prefix get_. I have thus updated the Project.toml.

I will take a look at #144 (comment).

I have also restructured the code to simplify in the future documentation, the organisation of the presentation the model, the solution and their setters and getters.

@PierreMartinon @jbcaillau Please comment.

[ocots]

@jbcaillau We should make the v0.12.5 release before merging this PR.

[jbcaillau]

@jbcaillau We should make the v0.12.5 release before merging this PR.

👍🏽 go ahead!

[ocots]

@jbcaillau We should make the v0.12.5 release before merging this PR.

👍🏽 go ahead!

Done!

[ocots]

In the future documentation, if we use the getters, then, we will have something like:

sol = solve(ocp)
x = get_state(sol)

Do we prefer:

sol = solve(ocp)
x = state(sol)

Here is the list of getters:

# OptimalControlModel

get_dim_control_constraints
get_dim_state_constraints
get_dim_mixed_constraints
get_dim_path_constraints
get_dim_boundary_constraints
get_dim_variable_constraints
get_dim_control_range
get_dim_state_range,
get_dim_variable_range
get_model_expression
get_initial_time
get_initial_time_name
get_final_time
get_final_time_name
get_time_name
get_control_dimension
get_control_components_names
get_control_name
get_state_dimension
get_state_components_names
get_state_name
get_variable_dimension
get_variable_components_names
get_variable_name
get_lagrange
get_mayer
get_criterion
get_dynamics

# in the previous getters, some are common with OptimalControlSolution

# OptimalControlSolution

get_times
get_control
get_state, get_variable
get_costate
get_objective
get_iterations
get_stopping
get_message
get_success
get_infos

[ocots]

The most used by the user I guess are those on an OptimalControlSolution. Maybe, we can keep _get for those on an OptimalControlModel and for the others:

times    # or time_grid since times is very common
control # this will be used to define also some control law. Will be there any conflict?
state
variable
costate
objective
iterations
stopping
message
success
infos

If we have that, not clear to write something like: success = success(sol) or state = state(sol).

Usually we would write:

times = time_grid(sol)
u = control(sol)
x = state(sol)
v = variable(sol)
p = costate(sol)
obj = objective(sol)
Niter = iterations(sol)
stopping # ??
message # ??
success # ??
infos # ??

[ocots]

@PierreMartinon @jbcaillau Please make a comment.

[jbcaillau]

@PierreMartinon @jbcaillau Please make a comment.

Thanks @ocots I like this best:

times = time_grid(sol)
u = control(sol)
x = state(sol)
v = variable(sol)
p = costate(sol)
obj = objective(sol)
Niter = iterations(sol)
...

• actually, does it make sense (and is it a good / common practice in Julia) to use field(sol) for the getter, and field!(sol, val) for the setter?
• in the end, if there are not clear choice, we can also keep the two with aliases (state = get_state, etc.)

[ocots]

If you have several types, getters are a good idea. We just have one but with getters we can make some checkings, some computations, etc.

Maybe we can have both as you said with aliases.

We can make the aliases inside OptimalControl.jl and let in CTBase.jl the functiins with get_.

[ocots]

@jbcaillau @PierreMartinon I will rename some getters to have something like

times = time_grid(sol)
u = control(sol)
x = state(sol)
v = variable(sol)
p = costate(sol)
obj = objective(sol)
Niter = iterations(sol)
...

[ocots]

I have removed all the prefixes get_.

I make a push soon.