# Complement

The concrete complement can be computed with the function complement (with a lower-case "c").

LazySets.ComplementType
Complement{N, S<:LazySet{N}} <: LazySet{N}

Type that represents the complement of a set, i.e., the set

$$$Y = \{y ∈ ℝ^n : y ∉ X\}.$$$

The complement is often denoted with the $C$ superscript, as in $Y = X^C$.

Fields

• X – set

Notes

If X is empty, the universe, or a half-space, its complement is convex.

Since X is assumed to be closed, unless X is empty or the universe, its complement is open (i.e., not closed). In this library, all sets are closed, so the set is usually not represented exactly at the boundary.

The complement of the complement is the original set again.

Examples

julia> B = BallInf(zeros(2), 1.);

julia> C = Complement(B)
Complement{Float64, BallInf{Float64, Vector{Float64}}}(BallInf{Float64, Vector{Float64}}([0.0, 0.0], 1.0))

julia> Complement(C)
BallInf{Float64, Vector{Float64}}([0.0, 0.0], 1.0)
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LazySets.API.dimMethod
dim(C::Complement)

Return the dimension of the complement of a set.

Input

• C – complement of a set

Output

The ambient dimension of the complement of a set.

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Base.:∈Method
∈(x::AbstractVector, C::Complement)

Check whether a given point is contained in the complement of a set.

Input

• x – point/vector
• C – complement of a set

Output

true iff the vector is contained in the complement.

Algorithm

$$$x ∈ X^C ⟺ x ∉ X$$$
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Base.isemptyMethod
isempty(C::Complement)

Check whether the complement of a set is empty.

Input

• C – complement of a set

Output

false unless the original set is universal.

Algorithm

We use the isuniversal function.

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LazySets.API.constraints_listMethod
constraints_list(C::Complement)

Return the list of constraints of the complement of a set.

Input

• C – complement of a set

Output

A vector of linear constraints.

Notes

The method requires that the list of constraints of the complemented set can be obtained. Then, each constraint is complemented and returned in the output vector. The set union of this array corresponds to the concrete set complement.

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