Merge pull request #218 from JuliaReach/schillic/212

#212 - use ngens function

src/Zonotope.jl

@@ -136,7 +136,7 @@ For high dimensions, it would be preferable to develop a `vertex_iterator`
 approach.
 """
 function vertices_list(Z::Zonotope{N})::Vector{Vector{N}} where {N<:Real}
-    p = size(Z.generators, 2)
+    p = ngens(Z)
     vlist = Vector{Vector{N}}()
     sizehint!(vlist, 2^p)
 
@@ -258,7 +258,7 @@ The order of a zonotope is defined as the quotient of its number of generators
 and its dimension.
 """
 function order(Z::Zonotope)::Rational
-    return size(Z.generators, 2) // dim(Z)
+    return ngens(Z) // dim(Z)
 end
 
 """

src/is_intersection_empty.jl

@@ -367,7 +367,7 @@ function is_intersection_empty(Z::Zonotope{N},
                                witness::Bool=false
                               )::Union{Bool, Tuple{Bool, Vector{N}}} where {N<:Real}
     v = H.b - dot(H.a, Z.center)
-    abs_sum = sum(abs(dot(H.a, Z.generators[:, i])) for i = 1:size(Z.generators, 2))
+    abs_sum = sum(abs(dot(H.a, Z.generators[:, i])) for i = 1:ngens(Z))
     empty_intersection = v < -abs_sum || v > abs_sum
 
     if !witness