add PermAut(omorphisms)

src/groups/transvections.jl

@@ -81,3 +81,26 @@ Base.@propagate_inbounds function evaluate!(v::NTuple{T, N}, t::Transvection, A:
 
     return v
 end
+
+struct PermAut <: GSymbol
+    perm::Vector{UInt8}
+
+    function PermAut(p::AbstractVector{<:Integer})
+        @assert sort(p) == 1:length(p)
+        return new(p)
+    end
+end
+
+function Base.show(io::IO, p::PermAut)
+    print(io, 'σ')
+    join(io, (subscriptify(Int(i)) for i in p.perm))
+end
+
+Base.inv(p::PermAut) = PermAut(invperm(p.perm))
+
+Base.:(==)(p::PermAut, q::PermAut) = p.perm == q.perm
+Base.hash(p::PermAut, h::UInt) = hash(p.perm, hash(PermAut, h))
+
+Base.@propagate_inbounds function evaluate!(v::NTuple{T, N}, p::PermAut, ::Alphabet, tmp=one(first(v))) where {T, N}
+    return v[p.perm]
+end