implemented unitcelltype function

src/Box.jl

@@ -90,6 +90,36 @@ Base.@kwdef struct Box{UnitCellType,N,T,TSQ,M}
     unit_cell_max::SVector{N,T}
 end
 
+"""
+    unitcelltype(::Box{T}) where T = T
+
+Returns the type of a unitcell from the `Box` structure.
+
+## Example
+
+```julia-repl
+julia> box = Box([1,1,1], 0.1)
+
+julia> unitcelltype(box)
+OrthorhombicCell
+
+julia> box = Box([1 0 0; 0 1 0; 0 0 1], 0.1)
+
+julia> unitcelltype(box)
+TriclinicCell
+```
+
+"""
+unitcelltype(::Box{T}) where T = T
+
+@testitem "unitcelltype" begin
+    using CellListMap
+    @test unitcelltype(Box([1,1,1], 0.1)) == OrthorhombicCell
+    @test unitcelltype(Box([1 0 0; 0 1 0; 0 0 1], 0.1)) == TriclinicCell
+    x = rand(3,100)
+    @test unitcelltype(Box(limits(x), 0.1)) == NonPeriodicCell
+end
+
 """
 
 ```

src/CellListMap.jl

@@ -16,6 +16,7 @@ export limits
 export TriclinicCell
 export OrthorhombicCell
 export NonPeriodicCell
+export unitcelltype
 export nbatches
 export PeriodicSystem
 

src/PeriodicSystems.jl

@@ -6,12 +6,13 @@ using StaticArrays
 
 import ..CellListMap
 import ..CellListMap: INTERNAL
-import ..CellListMap: Box, update_box
+import ..CellListMap: Box, update_box, unitcelltype
 
 export PeriodicSystem
 export map_pairwise!, map_pairwise
 export update_cutoff!
 export update_unitcell!
+export unitcelltype
 
 export copy_output
 export resize_output!
@@ -182,6 +183,7 @@ function PeriodicSystem(;
     return sys
 end
 
+
 # Abstract type only for cleaner dispatch
 abstract type AbstractPeriodicSystem{OutputName} end
 
@@ -206,6 +208,14 @@ setproperty!(sys::AbstractPeriodicSystem, ::Val{:_box}, x) = setfield!(sys, :_bo
 setproperty!(sys::AbstractPeriodicSystem, ::Val{:_cell_list}, x) = setfield!(sys, :_cell_list, x)
 setproperty!(sys::AbstractPeriodicSystem, ::Val{:output}, x) = setfield!(sys, :output, x)
 
+"""
+    unitcelltype(sys::AbstractPeriodicSystem)
+
+Returns the type of a unitcell from the `PeriodicSystem` structure.
+
+"""
+unitcelltype(sys::AbstractPeriodicSystem) = unitcelltype(sys._box)
+
 @testitem "PeriodicSystems properties" begin
 
     using CellListMap.PeriodicSystems
@@ -245,6 +255,11 @@ setproperty!(sys::AbstractPeriodicSystem, ::Val{:output}, x) = setfield!(sys, :o
         @test PeriodicSystems.map_pairwise((x,y,i,j,d2,out) -> out += d2, sys) == 0.0
     end
 
+    # unitcell type
+    x = rand(SVector{3,Float64},100)
+    @test unitcelltype(PeriodicSystem(positions=x, cutoff=0.1, unitcell=[1,1,1], output=0.0)) == OrthorhombicCell
+    @test unitcelltype(PeriodicSystem(positions=x, cutoff=0.1, unitcell=[1 0 0; 0 1 0; 0 0 1], output=0.0)) == TriclinicCell
+
 end
 
 """