improved some assertion messages

as suggested by @fieker

src/Groups/libraries/perfectgroups.jl

@@ -16,7 +16,8 @@ perfect groups in GAP's Perfect Groups Library.
 The type `T` can be either `PermGroup` or `FPGroup`.
 """
 function perfect_group(::Type{T}, n::Int, m::Int) where T <: GAPGroup
-   @assert m<= number_perfect_groups(n) "There are less than $m perfect groups of order $n, up to isomorphism."
+   N = number_perfect_groups(n)
+   @assert m <= N "There are only $N perfect groups of order $n, up to isomorphism."
    if T==PermGroup
       G = T(GAP.Globals.PerfectGroup(GAP.Globals.IsPermGroup,n,m))
    elseif T==FPGroup

src/Groups/libraries/primitivegroups.jl

@@ -22,7 +22,8 @@ Return the `i`-th group in the catalogue of primitive groups of degree `n`
 in GAP's Primitive Groups Library. The output is a group of type `PermGroup`.
 """
 function primitive_group(deg::Int, n::Int)
-   @assert n<= number_primitive_groups(deg) "There are less than $n primitive groups of degree $deg."
+   N = number_primitive_groups(deg)
+   @assert n <= N "There are only $N primitive groups of degree $deg."
    return PermGroup(GAP.Globals.PrimitiveGroup(deg,n), deg)
 end
 

src/Groups/libraries/smallgroups.jl

@@ -19,7 +19,8 @@ The group is given of type `PcGroup` if the group is solvable,
 `PermGroup` otherwise.
 """
 function small_group(n::Int, m::Int)
-  @assert m<= number_small_groups(n) "There are less than $m groups of order $n, up to isomorphism."
+  N = number_small_groups(n)
+  @assert m <= N "There are only $N groups of order $n, up to isomorphism."
   G = GAP.Globals.SmallGroup(n, m)
   T = _get_type(G)
   return T(G)

src/Groups/libraries/transitivegroups.jl

@@ -21,7 +21,8 @@ Return the `i`-th group in the catalogue of transitive groups over the set
 The output is a group of type `PermGroup`.
 """
 function transitive_group(deg::Int, n::Int)
-   @assert n<= number_transitive_groups(deg) "There are less than $n transitive groups of degree $deg, up to permutation isomorphism."
+   N = number_transitive_groups(deg)
+   @assert n <= N "There are only $N transitive groups of degree $deg, up to permutation isomorphism."
 
    return PermGroup(GAP.Globals.TransitiveGroup(deg,n), deg)
 end

test/Groups/libraries.jl

@@ -32,6 +32,8 @@
    @test issemiregular(H)
    @test !isregular(H)
    @test isregular(H,[1,2])
+
+   @test_throws AssertionError transitive_group(1, 2)
 end
 
 @testset "Perfect groups" begin
@@ -47,6 +49,8 @@ end
    @test [number_perfect_groups(i) for i in 2:59]==[0 for i in 1:58]
    x = perfect_identification(alternating_group(5))
    @test isisomorphic(perfect_group(x[1],x[2]),alternating_group(5))[1]
+
+   @test_throws AssertionError perfect_group(60, 2)
 end
 
 @testset "Small groups" begin
@@ -62,4 +66,10 @@ end
    @test length(all_small_groups(16, isabelian))==5
    @test number_small_groups(16)==14
    @test number_small_groups(17)==1   
+
+   @test_throws AssertionError small_group(1, 2)
+end
+
+@testset "Primitive groups" begin
+   @test_throws AssertionError primitive_group(1, 1)
 end