lib/arc.js
function Arc(start, end, height) {
    this.start = start;
    this.end = end;
    this.height = height;
}
function Arc(start, end, height) {
    this.start = start;
    this.end = end;
    this.height = height;
}
function Arc ( start , end , height ) { this . start = start ; this . end = end ; this . height = height ; }
Define a simple Arc object
Define a simple Arc object