Removes unnecessary call to setdirty! in examples 1 and 3

[ferrolho]

Currently, somewhere in example 1 we can read:

RigidBodyDynamics.jl/examples/1. Quickstart - double pendulum/1. Quickstart - double pendulum.jl

Lines 101 to 111 in 6c40de7

	# Let's first set the configurations and velocities of the joints:
	set_configuration!(state, shoulder, 0.3)
	set_configuration!(state, elbow, 0.4)
	set_velocity!(state, shoulder, 1.)
	set_velocity!(state, elbow, 2.);
	# **Important**: a `MechanismState` contains cache variables that depend on the configurations and velocities of the joints. These need to be invalidated when the configurations and velocities are changed. To do this, call
	setdirty!(state)

However, set_configuration! and set_velocity! already call setdirty! from within them:

RigidBodyDynamics.jl/src/mechanism_state.jl

Lines 397 to 401 in 6c40de7

	function set_configuration!(state::MechanismState, joint::Joint, config)
	set_configuration!(configuration(state, joint), joint, config)
	reset_contact_state!(state)
	setdirty!(state)
	end

RigidBodyDynamics.jl/src/mechanism_state.jl

Lines 409 to 413 in 6c40de7

	function set_velocity!(state::MechanismState, joint::Joint, vel)
	set_velocity!(velocity(state, joint), joint, vel)
	reset_contact_state!(state)
	setdirty!(state)
	end

Perhaps the call to setdirty! is in the examples because in some older version of RBD.jl set_configuration! and set_velocity! didn't invalidate the caches?

[rdeits]

Yup, makes sense to me. What do you think, @tkoolen?

[tkoolen]

Yeah, I suppose this is fine. It's certainly not necessary in these cases and I think it's there for mostly historical reasons, but it'd be good to mention somewhere that there's a need to invalidate the cache manually if you modify q and v without using these methods. I'll try to find a better place for that.

[tkoolen]

And sorry I've been out of the loop for so long.

[ferrolho]

but it'd be good to mention somewhere that there's a need to invalidate the cache manually

It is mentioned here

RigidBodyDynamics.jl/src/mechanism_state.jl

Lines 355 to 366 in 191fca7

	"""
	$(SIGNATURES)
	Return the configuration vector ``q``.
	Note that this returns a reference to the underlying data in `state`. The user
	is responsible for calling [`setdirty!`](@ref) after modifying this vector to
	ensure that dependent cache variables are invalidated.
	"""
	configuration(state::MechanismState) = state.q

and here

RigidBodyDynamics.jl/src/mechanism_state.jl

Lines 366 to 377 in 191fca7

	"""
	$(SIGNATURES)
	Return the velocity vector ``v``.
	Note that this function returns a read-write reference to a field in `state`.
	The user is responsible for calling [`setdirty!`](@ref) after modifying this
	vector to ensure that dependent cache variables are invalidated.
	"""
	velocity(state::MechanismState) = state.v

(And now there's this issue, too.) 😛

[ferrolho]

And sorry I've been out of the loop for so long.

I don't see why you have to apologise. I'm sure people know this is something you do pro bono. 🙂