Rename rank(A::GrpAbFinGen) to torsion_free_rank

Unfortunately the notion of 'rank' for groups clashes with that for abelian groups.
The latter is also known as 'torsion free rank'. Hence I propose to rename `rank`
for abelian groups here accordingly.

docs/src/abelian/introduction.md

@@ -59,6 +59,7 @@ rels(A::GrpAbFinGen)
 is_finite(A::GrpAbFinGen)
 is_infinite(A::GrpAbFinGen)
 rank(A::GrpAbFinGen)
+torsion_free_rank(A::GrpAbFinGen)
 order(A::GrpAbFinGen)
 exponent(A::GrpAbFinGen)
 is_trivial(A::GrpAbFinGen)

src/GrpAb/GrpAbFinGen.jl

@@ -33,7 +33,7 @@
 ################################################################################
 
 export abelian_group, free_abelian_group, is_snf, ngens, nrels, rels, snf, isfinite,
-       is_infinite, rank, order, exponent, is_trivial, is_isomorphic,
+       is_infinite, torsion_free_rank, rank, order, exponent, is_trivial, is_isomorphic,
        direct_product, is_torsion, torsion_subgroup, sub, quo, is_cyclic,
        psylow_subgroup, is_subgroup, abelian_groups, flat, tensor_product,
        dual, chain_complex, is_exact, free_resolution, obj, map,
@@ -477,19 +477,23 @@ is_finite_gen(A::GrpAbFinGen) = isfinite(snf(A)[1])
 ################################################################################
 
 @doc raw"""
-    rank(A::GrpAbFinGen) -> Int
+    torsion_free_rank(A::GrpAbFinGen) -> Int
 
-Return the rank of $A$, that is, the dimension of the
+Return the torsion free rank of $A$, that is, the dimension of the
 $\mathbf{Q}$-vectorspace $A \otimes_{\mathbf Z} \mathbf Q$.
+
+See also [`rank`](@ref).
 """
-rank(A::GrpAbFinGen) = is_snf(A) ? rank_snf(A) : rank_gen(A)
+torsion_free_rank(A::GrpAbFinGen) = is_snf(A) ? torsion_free_rank_snf(A) : torsion_free_rank_gen(A)
 
-rank_snf(A::GrpAbFinGen) = length(findall(x -> iszero(x), A.snf))
+torsion_free_rank_snf(A::GrpAbFinGen) = length(findall(iszero, A.snf))
 
-rank_gen(A::GrpAbFinGen) = rank(snf(A)[1])
+torsion_free_rank_gen(A::GrpAbFinGen) = torsion_free_rank(snf(A)[1])
 
+# TODO: document what this does?
 rank(A::GrpAbFinGen, p::Union{Int, ZZRingElem}) = is_snf(A) ? rank_snf(A, p) : rank_snf(snf(A)[1], p)
 
+# TODO: document what this does?
 function rank_snf(A::GrpAbFinGen, p::Union{Int, ZZRingElem})
   if isempty(A.snf)
     return 0
@@ -502,6 +506,17 @@ function rank_snf(A::GrpAbFinGen, p::Union{Int, ZZRingElem})
 end
 
 
+@doc raw"""
+    rank(A::GrpAbFinGen) -> Int
+
+Return the rank of $A$, that is, the size of a minimal generating set for $A$.
+
+See also [`torsion_free_rank`](@ref).
+"""
+rank(A::GrpAbFinGen) = error("rank(::GrpAbFinGen) has been renamed to torsion_free_rank")
+#rank(A::GrpAbFinGen) = is_snf(A) ? length(A.snf) : return rank(snf(A)[1])
+
+
 ################################################################################
 #
 #  Order

test/GrpAb/GrpAbFinGen.jl

@@ -130,16 +130,20 @@
 
   @testset "Rank" begin
     G = abelian_group([3, 15])
-    @test @inferred rank(G) == 0
+    @test @inferred torsion_free_rank(G) == 0
+    #@test @inferred rank(G) == 2
 
     G = abelian_group([3, 5])
-    @test @inferred rank(G) == 0
+    @test @inferred torsion_free_rank(G) == 0
+    #@test @inferred rank(G) == 1
 
     G = abelian_group([3, 15, 0])
-    @test @inferred rank(G) == 1
+    @test @inferred torsion_free_rank(G) == 1
+    #@test @inferred rank(G) == 3
 
     G = abelian_group([3, 5, 0])
-    @test @inferred rank(G) == 1
+    @test @inferred torsion_free_rank(G) == 1
+    #@test @inferred rank(G) == 2
   end
 
   @testset "Order" begin