return HPolytope in projection of polytope

JuliaReach · Jun 25, 2020 · 4895b6a · 4895b6a
1 parent 55528b6
commit 4895b6a
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diff --git a/src/Approximations/decompositions.jl b/src/Approximations/decompositions.jl
@@ -569,8 +569,10 @@ Concrete projection of a polyhedral set.
 
 ### Output
 
-An `HPolyhedron` representing the projection of `P` on the dimensions specified
-by `block`.
+A polyhedron representing the projection of `P` on the dimensions specified by
+`block`.
+If `P` was bounded, the result is an `HPolytope`; otherwise the result is an
+`HPolyhedron`.
 
 ### Algorithm
 
@@ -600,7 +602,7 @@ julia> constrained_dimensions(P)
 
 julia> P_1234 = project(P, [1, 2, 3, 4]);
 
-julia> P_1234 == convert(HPolyhedron, P)
+julia> P_1234 == convert(HPolytope, P)
 true
 ```
 Each constraint of the cross polytope is constrained in all dimensions.
@@ -641,7 +643,8 @@ function project(P::AbstractPolyhedron{N}, block::AbstractVector{Int}) where {N}
         lm = linear_map(M, P)
         clist = constraints_list(lm)
     end
-    return HPolyhedron(clist)
+    T = isbounded(P) ? HPolytope : HPolyhedron
+    return T(clist)
 end
 
 function project(Z::Zonotope{N}, block::AbstractVector{Int}) where {N}

diff --git a/test/unit_Polytope.jl b/test/unit_Polytope.jl
@@ -473,5 +473,11 @@ for N in [Float64]
         c3, r = chebyshev_center(P; get_radius=true)
         @test c1 == c2 == c3 == center(B) && c1 isa AbstractVector{N}
         @test r == B.radius
+
+        # concrete projection
+        πP = project(P, [1])
+        @test πP isa HPolytope{N}
+        @test ispermutation(constraints_list(πP), [HalfSpace(N[-1], N(1)),
+                                                   HalfSpace(N[1], N(1))])
     end
 end