interface definitions with nomenclature

[soypat]

It would be of great use if interfaces where arguments are ambiguous, for example Observer and Filter, named their arguments according to control theory typical nomenclature.

This is current interface definition

// Filter is a dynamical system filter.
type Filter interface {
	// Predict estimates the next internal state of the system
	Predict(mat.Vector, mat.Vector) (Estimate, error)
	// Update updates the system state based on external measurement
	Update(mat.Vector, mat.Vector, mat.Vector) (Estimate, error)
}

// Propagator propagates internal state of the system to the next step
type Propagator interface {
	// Propagate propagates internal state of the system to the next step
	Propagate(mat.Vector, mat.Vector, mat.Vector) (mat.Vector, error)
}

// Observer observes external state (output) of the system
type Observer interface {
	// Observe observes external state of the system
	Observe(mat.Vector, mat.Vector, mat.Vector) (mat.Vector, error)
}

Problems with this definition include:

• All arguments are mat.Vector. What convention is being used?
• Comments do not help either. Overall lackluster documentation

Other interfaces with this problem:

• filter.DiscreteModel. This one is fixed easy: StateMatrix() (A mat.Matrix). A,B,C and D matrices are standard nomenclature for these matrices

Possible solutions

Below is a mix of adding a little bit of documentation + naming the variables.

type Filter interface {
	// Predict estimates the next internal state of the system. x is state, u are inputs
	Predict(x,u mat.Vector) (filter.Estimate, error)
	// Update updates the system state based on external measurement. x is state, u are inputs, z is the measurement
	Update(x, u, z mat.Vector) (filter.Estimate, error) 
}

[soypat]

If you give me the all-clear I can try fixing it tonight and PRing. This and #7

[milosgajdos]

Happy to accept a PR for this. This sounds like a great idea.