gistfile1.lua

function vec(x, y)
    return {x, y}
end

v = vec -- shortcut

function dot(v1, v2)
    return v1[1]*v2[1] + v1[2]*v2[2]
end

function normalize(v)
    local mag = math.sqrt(v[1]^2 + v[2]^2)
    return vec(v[1]/mag, v[2]/mag)
end

function perp(v)
    return {v[2],-v[1]}
end

function segment(a, b)
    local obj = {a=a, b=b, dir={b[1] - a[1], b[2] - a[2]}}
    obj[1] = obj.dir[1]; obj[2] = obj.dir[2]
    return obj
end

function polygon(vertices)
    local obj = {}
    obj.vertices = vertices
    obj.edges = {}
    for i=1,#vertices do
        table.insert(obj.edges, segment(vertices[i], vertices[1+i%(#vertices)]))
    end
    return obj
end