Abstractify method signatures. Solves #2

src/interface_implementations/ballandbeam.jl

@@ -49,10 +49,10 @@ const AbstractBeamOrBallAndBeam = Union{AbstractBeam, AbstractBallAndBeam}
 num_outputs(p::AbstractBeam)             = 1
 num_outputs(p::AbstractBallAndBeam)      = 2
 num_inputs(p::AbstractBeamOrBallAndBeam) = 1
-outputrange(p::Beam)                     = [(-10,10)]
+outputrange(p::AbstractBeam)             = [(-10,10)]
 outputrange(p::AbstractBallAndBeam)      = [(-10,10),(-1,1)] # Beam angle, Ball position
 inputrange(p::AbstractBeamOrBallAndBeam) = [(-10,10)]
-isstable(p::Beam)                        = true
+isstable(p::AbstractBeam)                = true
 isstable(p::AbstractBallAndBeam)         = false
 isasstable(p::AbstractBeamOrBallAndBeam) = false
 sampletime(p::AbstractBeamOrBallAndBeam) = p.h