ControlSystems compat part 3: Axes. Closes #84

Author: jonniedie

src/axis.jl

@@ -119,11 +119,16 @@ julia> ca.c.b
 struct Axis{IdxMap} <: AbstractAxis{IdxMap} end
 @inline Axis(IdxMap::NamedTuple) = Axis{IdxMap}()
 Axis(;kwargs...) = Axis((;kwargs...))
+function Axis(symbols::Union{AbstractVector{Symbol}, NTuple{N,Symbol}}) where N
+    return Axis(NamedTuple(symbols .=> eachindex(symbols)))
+end
+Axis(symbols::Symbol...) = Axis(symbols)
 
 Axis(ax::AbstractAxis) = ax
 Axis(ax::PartitionedAxis) = ax.ax
 Axis(ax::ViewAxis) = ax.ax
 
+# Get rid of this
 Axis(::Number) = NullAxis()
 Axis(::NamedTuple{()}) = FlatAxis()
 Axis(x) = FlatAxis()

test/runtests.jl

@@ -68,6 +68,11 @@ end
     @test_throws DimensionMismatch ComponentMatrix(rand(11,11,11), ax, ax)
     @test_throws ErrorException ComponentArray(v=[(a=1, b=2), (a=3, c=4)])
 
+    # Axis construction from symbols
+    @test Axis([:a, :b, :c]) == Axis(a=1, b=2, c=3)
+    @test Axis((:a, :b, :c)) == Axis(a=1, b=2, c=3)
+    @test Axis(:a, :b, :c) == Axis(a=1, b=2, c=3)
+
     # Issue #24
     @test ComponentVector(a=1, b=2f0) == ComponentVector{Float32}(a = 1.0, b = 2.0)
     @test ComponentVector(a=1, b=2+im) == ComponentVector{Complex{Int64}}(a = 1 + 0im, b = 2 + 1im)