move show functions to abstract.jl

src/matrix_groups/SLn.jl

@@ -21,22 +21,14 @@ end
 
 GroupsCore.ngens(SL::SpecialLinearGroup{N}) where {N} = N^2 - N
 
-Base.show(io::IO, SL::SpecialLinearGroup{N,T}) where {N,T} =
-    print(io, "special linear group of $N×$N matrices over $T")
+function Base.show(io::IO, ::SpecialLinearGroup{N,T}) where {N,T}
+    return print(io, "SL{$N,$T}")
+end
 
 function Base.show(
     io::IO,
     ::MIME"text/plain",
-    sl::Groups.AbstractFPGroupElement{<:SpecialLinearGroup{N}}
-) where {N}
-
-    Groups.normalform!(sl)
-
-    print(io, "SL{$N,$(eltype(sl))} matrix: ")
-    KnuthBendix.print_repr(io, word(sl), alphabet(sl))
-    println(io)
-    Base.print_array(io, matrix_repr(sl))
+    SL::SpecialLinearGroup{N,T},
+) where {N,T}
+    return print(io, "special linear group of $N×$N matrices over $T")
 end
-
-Base.show(io::IO, sl::Groups.AbstractFPGroupElement{<:SpecialLinearGroup}) =
-    KnuthBendix.print_repr(io, word(sl), alphabet(sl))

src/matrix_groups/Spn.jl

@@ -21,20 +21,11 @@ end
 
 GroupsCore.ngens(Sp::SymplecticGroup) = length(Sp.gens)
 
-Base.show(io::IO, ::SymplecticGroup{N}) where {N} = print(io, "group of $N×$N symplectic matrices")
+Base.show(io::IO, ::SymplecticGroup{N,T}) where {N,T} = print(io, "Sp{$N,$T}")
 
-function Base.show(
-    io::IO,
-    ::MIME"text/plain",
-    sp::Groups.AbstractFPGroupElement{<:SymplecticGroup{N}}
-) where {N}
-    Groups.normalform!(sp)
-    print(io, "$N×$N symplectic matrix: ")
-    KnuthBendix.print_repr(io, word(sp), alphabet(sp))
-    println(io)
-    Base.print_array(io, matrix_repr(sp))
+function Base.show(io::IO, ::MIME"text/plain", ::SymplecticGroup{N}) where {N}
+    return print(io, "group of $N×$N symplectic matrices")
 end
-
 _offdiag_idcs(n) = ((i, j) for i in 1:n for j in 1:n if i ≠ j)
 
 function symplectic_gens(N, T=Int8)

src/matrix_groups/abstract.jl

@@ -38,3 +38,29 @@ function Base.rand(
     S = gens(Mgroup)
     return prod(g -> rand(rng, Bool) ? g : inv(g), rand(rng, S, rand(rng, 1:30)))
 end
+
+function Base.show(io::IO, M::AbstractMatrixGroup)
+    g = gens(M, 1)
+    N = size(g, 1)
+    print(io, "H ⩽ GL{$N,$(eltype(g))}")
+end
+
+function Base.show(io::IO, ::MIME"text/plain", M::AbstractMatrixGroup)
+    N = size(gens(M, 1), 1)
+    ng = GroupsCore.ngens(M)
+    print(io, "subgroup of $N×$N invertible matrices with $(ng) generators")
+end
+
+Base.show(io::IO, mat::Groups.AbstractFPGroupElement{<:AbstractMatrixGroup}) =
+    KnuthBendix.print_repr(io, word(mat), alphabet(mat))
+
+function Base.show(
+    io::IO,
+    ::MIME"text/plain",
+    mat::Groups.AbstractFPGroupElement{<:AbstractMatrixGroup{N}}
+) where {N}
+    Groups.normalform!(mat)
+    KnuthBendix.print_repr(io, word(mat), alphabet(mat))
+    println(io, " ∈ ", parent(mat))
+    Base.print_array(io, matrix(mat))
+end