Access to the values of an axis by name using getproperty

This is particularly useful and succinct when you're working on domain
specific data with known axis names.

Author: Chris Foster

docs/src/index.md

@@ -79,8 +79,21 @@ And data, a 2400001×2 Array{Float64,2}:
 
 ```
 
-AxisArrays behave like regular arrays, but they additionally use the axis
-information to enable all sorts of fancy behaviors. For example, we can specify
+AxisArrays behave like regular arrays, but they carry extra information about
+their axes along with them:
+
+```jldoctest
+julia> A.time
+0.0 s:2.5e-5 s:60.0 s
+
+julia> A.chan
+2-element Array{Symbol,1}:
+ :c1
+ :c2
+
+```
+
+This enables all sorts of fancy indexing behaviors. For example, we can specify
 indices in *any* order, just so long as we annotate them with the axis name:
 
 ```jldoctest

src/core.jl

@@ -285,6 +285,18 @@ function axisdim(::Type{AxisArray{T,N,D,Ax}}, ::Type{<:Axis{name,S} where S}) wh
     idx
 end
 
+# Access to the values of axes by name
+function Base.getproperty(A::AxisArray, name::Symbol)
+    if name === :data || name === :axes
+        getfield(A, name)
+    else
+        # Other things are axis names
+        getfield(A, :axes)[axisdim(A, Axis{name})].val
+    end
+end
+# Expose only axis names to tab completion
+Base.propertynames(A::AxisArray) = axisnames(A)
+
 # Base definitions that aren't provided by AbstractArray
 @inline Base.size(A::AxisArray) = size(A.data)
 @inline Base.size(A::AxisArray, Ax::Axis) = size(A.data, axisdim(A, Ax))

test/core.jl

@@ -167,6 +167,14 @@ A = @inferred(AxisArray(reshape(1:24, 2,3,4),
 @test axisdim(A, Axis{:x}) == axisdim(A, Axis{:x}()) == 1
 @test axisdim(A, Axis{:y}) == axisdim(A, Axis{:y}()) == 2
 @test axisdim(A, Axis{:z}) == axisdim(A, Axis{:z}()) == 3
+# Test that getproperty is fully inferred when a const name is supplied
+let getx(A) = A.x,
+    getz(A) = A.z
+    @test @inferred(getx(A)) == A.axes[1].val
+    @test @inferred(getz(A)) == A.axes[3].val
+end
+@test propertynames(A) == (:x, :y, :z)
+
 # Test axes
 @test @inferred(AxisArrays.axes(A)) == (Axis{:x}(.1:.1:.2), Axis{:y}(1//10:1//10:3//10), Axis{:z}(["a", "b", "c", "d"]))
 @test @inferred(AxisArrays.axes(A, Axis{:x})) == @inferred(AxisArrays.axes(A, Axis{:x}())) == Axis{:x}(.1:.1:.2)