Add SA_F64, SA_F32 for constructing common eltype

This gives a way to construct an `SVector` and `SMatrix` with a precise
eltype, but without typing a verbose type name.

I think this fixes #24 to the extent that it can be fixed.

Also add some quickstart docs for `SA` and the new type aliases.

Author: c42f

README.md

@@ -62,6 +62,13 @@ Pkg.add("StaticArrays")  # or Pkg.clone("https://github.com/JuliaArrays/StaticAr
 using StaticArrays
 using LinearAlgebra
 
+# Use the convenience constructor type `SA` to create vectors and matrices
+SA[1, 2, 3]     isa SVector{3,Int}
+SA_F64[1, 2, 3] isa SVector{3,Float64}
+SA_F32[1, 2, 3] isa SVector{3,Float32}
+SA[1 2; 3 4]     isa SMatrix{2,2,Int}
+SA_F64[1 2; 3 4] isa SMatrix{2,2,Float64}
+
 # Create an SVector using various forms, using constructors, functions or macros
 v1 = SVector(1, 2, 3)
 v1.data === (1, 2, 3) # SVector uses a tuple for internal storage

docs/src/pages/quickstart.md

@@ -5,6 +5,13 @@ Pkg.add("StaticArrays")  # or Pkg.clone("https://github.com/JuliaArrays/StaticAr
 using StaticArrays
 using LinearAlgebra
 
+# Use the convenience constructor type `SA` to create vectors and matrices
+SA[1, 2, 3]     isa SVector{3,Int}
+SA_F64[1, 2, 3] isa SVector{3,Float64}
+SA_F32[1, 2, 3] isa SVector{3,Float32}
+SA[1 2; 3 4]     isa SMatrix{2,2,Int}
+SA_F64[1 2; 3 4] isa SMatrix{2,2,Float64}
+
 # Create an SVector using various forms, using constructors, functions or macros
 v1 = SVector(1, 2, 3)
 v1.data === (1, 2, 3) # SVector uses a tuple for internal storage

src/StaticArrays.jl

@@ -36,7 +36,7 @@ export SHermitianCompact
 
 export Size, Length
 
-export SA
+export SA, SA_F32, SA_F64
 export @SVector, @SMatrix, @SArray
 export @MVector, @MMatrix, @MArray
 

src/initializers.jl

@@ -12,9 +12,17 @@ provided explicitly.
 * `SA[1 2; 3 4]` creates a 2×2 SMatrix of `Int`s.
 * `SA[1 2]` creates a 1×2 SMatrix of `Int`s.
 * `SA{Float32}[1, 2]` creates a length-2 `SVector` of `Float32` elements.
+
+A couple of helpful type aliases are also provided:
+
+* `SA_F64[1, 2]` creates a lenght-2 `SVector` of `Float64` elements
+* `SA_F32[1, 2]` creates a lenght-2 `SVector` of `Float32` elements
 """
 struct SA{T} ; end
 
+const SA_F32 = SA{Float32}
+const SA_F64 = SA{Float64}
+
 @inline similar_type(::Type{SA}, ::Size{S}) where {S} = SArray{Tuple{S...}}
 @inline similar_type(::Type{SA{T}}, ::Size{S}) where {T,S} = SArray{Tuple{S...}, T}
 

test/initializers.jl

@@ -1,3 +1,5 @@
+@testset "Initialization with SA" begin
+
 SA_test_ref(x)   = SA[1,x,x]
 SA_test_ref(x,T) = SA{T}[1,x,x]
 @test @inferred(SA_test_ref(2))   === SVector{3,Int}((1,2,2))
@@ -31,3 +33,7 @@ SA_test_hvcat(x,T) = SA{T}[1 x x;
                                                                                        4 5]
 @test_throws ArgumentError("SA[...] matrix rows of length (2, 3) are inconsistent") SA[1 2;
                                                                                        3 4 5]
+@test SA_F64[1, 2] === SVector{2,Float64}((1,2))
+@test SA_F32[1, 2] === SVector{2,Float32}((1,2))
+
+end