Add fallback definitions for getindex(::SectorValues) and findindex(::SectorValues) (#6)

Author: lkdvos

src/anyons.jl

@@ -56,7 +56,7 @@ Base.length(::SectorValues{FibonacciAnyon}) = 2
 function Base.iterate(::SectorValues{FibonacciAnyon}, i=0)
     return i == 0 ? (FibonacciAnyon(:I), 1) : (i == 1 ? (FibonacciAnyon(:τ), 2) : nothing)
 end
-function Base.getindex(S::SectorValues{FibonacciAnyon}, i)
+function Base.getindex(S::SectorValues{FibonacciAnyon}, i::Int)
     if i == 1
         return FibonacciAnyon(:I)
     elseif i == 2
@@ -177,7 +177,7 @@ const all_isinganyons = (IsingAnyon(:I), IsingAnyon(:σ), IsingAnyon(:ψ))
 Base.IteratorSize(::Type{SectorValues{IsingAnyon}}) = HasLength()
 Base.length(::SectorValues{IsingAnyon}) = length(all_isinganyons)
 Base.iterate(::SectorValues{IsingAnyon}, i=1) = iterate(all_isinganyons, i)
-Base.getindex(S::SectorValues{IsingAnyon}, i) = getindex(all_isinganyons, i)
+Base.getindex(::SectorValues{IsingAnyon}, i::Int) = getindex(all_isinganyons, i)
 
 function findindex(::SectorValues{IsingAnyon}, a::IsingAnyon)
     a == all_isinganyons[1] && return 1

src/fermions.jl

@@ -23,7 +23,7 @@ Base.length(::SectorValues{FermionParity}) = 2
 function Base.iterate(::SectorValues{FermionParity}, i=0)
     return i == 2 ? nothing : (FermionParity(i), i + 1)
 end
-function Base.getindex(::SectorValues{FermionParity}, i)
+function Base.getindex(::SectorValues{FermionParity}, i::Int)
     return 1 <= i <= 2 ? FermionParity(i - 1) : throw(BoundsError(values(FermionParity), i))
 end
 findindex(::SectorValues{FermionParity}, f::FermionParity) = f.isodd ? 2 : 1

src/sectors.jl

@@ -46,15 +46,44 @@ instance is obtained as `values(I)`. For a new `I::Sector`, the following should
 If `IteratorSize(I) == HasLength()`, also the following must be implemented:
 *   `Base.length(::SectorValues{I})`: the number of different values
 *   `Base.getindex(::SectorValues{I}, i::Int)`: a mapping between an index `i` and an
-    instance of `I`
+    instance of `I`. A fallback implementation exists that returns the `i`th value
+    of the `SectorValues` iterator.
 *   `findindex(::SectorValues{I}, c::I)`: reverse mapping between a value `c::I` and an
-    index `i::Integer ∈ 1:length(values(I))`
+    index `i::Integer ∈ 1:length(values(I))`. A fallback implementation exists that
+    linearly searches through the `SectorValues` iterator.
 """
 struct SectorValues{I<:Sector} end
 Base.IteratorEltype(::Type{<:SectorValues}) = HasEltype()
 Base.eltype(::Type{SectorValues{I}}) where {I<:Sector} = I
 Base.values(::Type{I}) where {I<:Sector} = SectorValues{I}()
 
+Base.@propagate_inbounds function Base.getindex(v::SectorValues{I},
+                                                i::Int) where {I<:Sector}
+    @boundscheck begin
+        if Base.IteratorSize(v) === HasLength()
+            1 ≤ i ≤ length(v) || throw(BoundsError(v, i))
+        else
+            1 ≤ i || throw(BoundsError(v, i))
+        end
+    end
+    for (j, c) in enumerate(v)
+        j == i && return c
+    end
+    throw(BoundsError(v, i))
+end
+
+"""
+    findindex(v::SectorValues{I}, c::I)
+
+Reverse mapping between a value `c::I` and an index `i::Integer ∈ 1:length(values(I))`.
+"""
+function findindex(v::SectorValues{I}, c::I) where {I<:Sector}
+    for (i, cc) in enumerate(v)
+        cc == c && return i
+    end
+    throw(ArgumentError(lazy"Cannot locate sector $c"))
+end
+
 """
     one(::Sector) -> Sector
     one(::Type{<:Sector}) -> Sector

test/newsectors.jl

@@ -75,9 +75,4 @@ end
 Base.hash(s::NewSU2Irrep, h::UInt) = hash(s.j, h)
 Base.isless(s1::NewSU2Irrep, s2::NewSU2Irrep) = isless(s1.j, s2.j)
 
-function Base.getindex(::SectorValues{NewSU2Irrep}, i::Int)
-    return 1 <= i ? NewSU2Irrep(half(i - 1)) : throw(BoundsError(values(NewSU2Irrep), i))
-end
-TensorKitSectors.findindex(::SectorValues{NewSU2Irrep}, s::NewSU2Irrep) = twice(s.j) + 1
-
 end # module NewSectors