add OneHotVector (#179)

* add OneHotVector

* don't test against SingularIntegralEquations for now

* add basis

* fix test

* remove unnecessary test

* don't export basis

* coefficients returns Vector

* rename basis to basisfunction

Author: jishnub

.github/workflows/downstream.yml

@@ -23,7 +23,6 @@ jobs:
           - {repo: ApproxFunOrthogonalPolynomials.jl, group: JuliaApproximation}
           - {repo: ApproxFunFourier.jl, group: JuliaApproximation}
           - {repo: ApproxFunSingularities.jl, group: JuliaApproximation}
-          - {repo: SingularIntegralEquations.jl, group: JuliaApproximation}
 
     steps:
       - uses: actions/checkout@v2

Project.toml

@@ -1,6 +1,6 @@
 name = "ApproxFunBase"
 uuid = "fbd15aa5-315a-5a7d-a8a4-24992e37be05"
-version = "0.6.17"
+version = "0.6.18"
 
 [deps]
 AbstractFFTs = "621f4979-c628-5d54-868e-fcf4e3e8185c"

src/ApproxFunBase.jl

@@ -107,6 +107,7 @@ strictconvert(T::Type, x) = convert(T, x)::T
 
 include("LinearAlgebra/LinearAlgebra.jl")
 include("Fun.jl")
+include("onehotvector.jl")
 include("Domains/Domains.jl")
 include("Multivariate/Multivariate.jl")
 include("Operators/Operator.jl")

src/Fun.jl

@@ -45,7 +45,7 @@ function coefficients(f::Fun,msp::Space)
     #zero can always be converted
     fc = f.coefficients
     if ncoefficients(f) == 0 || (ncoefficients(f) == 1 && fc[1] == 0)
-        fc
+        convert(Vector, fc)
     else
         coefficients(fc, space(f), msp)
     end

src/onehotvector.jl

@@ -0,0 +1,11 @@
+struct OneHotVector{T} <: AbstractVector{T}
+	n :: Int
+	len :: Int
+end
+OneHotVector(n, len = n) = OneHotVector{Float64}(n, len)
+Base.size(v::OneHotVector) = (v.len,)
+Base.length(v::OneHotVector) = v.len
+function Base.getindex(v::OneHotVector{T}, i::Int) where {T}
+	i == v.n ? one(T) : zero(T)
+end
+basisfunction(sp, k) = Fun(sp, OneHotVector(k))

test/SpacesTest.jl

@@ -320,6 +320,15 @@ using BandedMatrices: rowrange, colrange, BandedMatrix
             f3 = Fun(space(f), Float64[1:4;])
             @test newvals(f2) ≈ values(f3)
             @test values(f2) ≈ values(f3)
+
+            @testset "OneHotVector" begin
+                for n in [1, 3, 10_000]
+                    f = Fun(Chebyshev(), [zeros(n-1); 1])
+                    g = ApproxFunBase.basisfunction(Chebyshev(), n)
+                    @test f == g
+                    @test f(0.5) == g(0.5)
+                end
+            end
         end
 
         @testset "multiplication of Funs" begin