add spaces and docs

src/HalfSpace.jl

@@ -206,4 +206,4 @@ See the documentation of `halfspace_left`.
 function halfspace_right(p::AbstractVector{N},
                          q::AbstractVector{N})::HalfSpace{N} where {N<:Real}
     return halfspace_right(q, p)
-end
+end

src/LineSegment.jl

@@ -145,6 +145,36 @@ function ∈(x::AbstractVector{N}, L::LineSegment{N})::Bool where {N<:Real}
            min(L.p[2], L.q[2]) <= x[2] <= max(L.p[2], L.q[2])
 end
 
+"""
+    halfspace_left(L::LineSegment)
+
+Return a half-space describing the 'left' of a two-dimensional line segment through
+two points.
+
+### Input
+
+ - `L` -- line segment
+
+### Output
+
+The half-space whose boundary goes through the two points `p` and `q` and which
+describes the left-hand side of the directed line segment `pq`.
+"""
 halfspace_left(L::LineSegment) = halfspace_left(L.p, L.q)
 
-halfspace_right(L::LineSegment) = halfspace_right(L.p, L.q)
+"""
+    halfspace_right(L::LineSegment)
+
+Return a half-space describing the 'right' of a two-dimensional line segment through
+two points.
+
+### Input
+
+ - `L` -- line segment
+
+### Output
+
+The half-space whose boundary goes through the two points `p` and `q` and which
+describes the right-hand side of the directed line segment `pq`.
+"""
+halfspace_right(L::LineSegment) = halfspace_right(L.p, L.q)