export interface IPoint { x: number y: number } export function pointSub(v1: IPoint, v2: IPoint) { return { x: v1.x - v2.x, y: v1.y - v2.y, } } export function pointAdd(v1: IPoint, v2: IPoint) { return { x: v1.x + v2.x, y: v1.y + v2.y, } } export const zeroPoint = { x: 0, y: 0 }