test show methods

src/groups/transvections.jl

@@ -31,12 +31,11 @@ end
 
 function Base.show(io::IO, t::Transvection)
     id = if t.id === :ϱ
-        "ϱ"
+        'ϱ'
     else # if t.id === :λ
-        "λ"
+        'λ'
     end
-    # print(io, id, Groups.subscriptify(t.i), ".", Groups.subscriptify(t.j))
-    print(io, id, "_", t.i, ",", t.j)
+    print(io, id, subscriptify(t.i), '.', subscriptify(t.j))
     t.inv && print(io, "^-1")
 end
 

src/new_types.jl

@@ -211,3 +211,8 @@ end
 
 abstract type GSymbol end
 Base.literal_pow(::typeof(^), t::GSymbol, ::Val{-1}) = inv(t)
+
+function subscriptify(n::Integer)
+    subscript_0 = Int(0x2080) # Char(0x2080) -> subscript 0
+    return join([Char(subscript_0 + i) for i in reverse(digits(n))], "")
+end

test/AutFn.jl

@@ -23,6 +23,9 @@
         @test New.gersten_alphabet(3) isa Alphabet
         A = New.gersten_alphabet(3)
         @test length(A) == 12
+
+        @test sprint(show, New.ϱ(1, 2)) == "ϱ₁.₂"
+        @test sprint(show, New.λ(3, 2)) == "λ₃.₂"
     end
 
     A4 = Alphabet(
@@ -36,8 +39,6 @@
     )
 
     F4 = New.FreeGroup([:a, :b, :c, :d], A4)
-    A = New.SpecialAutomorphismGroup(F4, maxrules=1000)
-
     a,b,c,d = gens(F4)
     D = ntuple(i->gens(F4, i), 4)
 
@@ -78,12 +79,14 @@
         @test inv(l)(deepcopy(D)) == (a, d^-1*b,c, d)
     end
 
+    A = New.SpecialAutomorphismGroup(F4, maxrules=1000)
+
     @testset "AutomorphismGroup constructors" begin
         @test A isa New.AbstractFPGroup
         @test A isa New.AutomorphismGroup
         @test KnuthBendix.alphabet(A) isa Alphabet
         @test New.relations(A) isa Vector{<:Pair}
-
+        @test sprint(show, A) == "automorphism group of free group on 4 generators"
     end
 
     @testset "Automorphisms: hash and evaluate" begin
@@ -93,6 +96,8 @@
         @test New.evaluate(g*h) == New.evaluate(h*g)
         @test (g*h).savedhash == zero(UInt)
 
+        @test sprint(show, typeof(g)) == "Automorphism{Groups.New.FreeGroup{Symbol},…}"
+
         a = g*h
         b = h*g
         @test hash(a) != zero(UInt)

test/fp_groups.jl

@@ -14,6 +14,7 @@
     G = New.FPGroup(F, [a*b=>b*a, a*c=>c*a, b*c=>c*b])
 
     @test G isa New.FPGroup
+    @test sprint(show, G) == "⟨a, b, c | a*b => b*a, a*c => c*a, b*c => c*b⟩"
     @test rand(G) isa New.FPGroupElement
 
     f = a*c*b
@@ -33,6 +34,11 @@
     New.normalform!(g)
     @test New.word(g) == [1, 3, 5]
 
+    let g = aG*cG*bG
+        # test that we normalize g before printing
+        @test sprint(show, g) == "a*b*c"
+    end
+
     # quotient of G
     H = New.FPGroup(G, [aG^2=>cG, bG*cG=>aG], maxrules=200)