let xmin = -2.0
let xmax = 1.0
let ymin = -1.0
let ymax = 1.0

let xstep = Int(CommandLine.arguments[1]) ?? 0
let ystep = Int(CommandLine.arguments[2]) ?? 0
let iters = Int(CommandLine.arguments[3]) ?? 0

func escapes(cr: Double, ci: Double, it: Int) -> Character {
    var zr: Double = 0.0
    var zi: Double = 0.0
    var zrtmp: Double

    for _ in 1...it {
        // z <- z^2 + c
        zrtmp = zr*zr - zi*zi + cr
        zi = 2*zr*zi + ci
        zr = zrtmp
        if zr*zr + zi*zi > 4 {
            return " "
        }
    }
    return "X"
}

for yc in 0...ystep-1 {
    let y = Double(yc)*(ymax-ymin)/Double(ystep) + ymin
    for xc in 0...xstep-1 {
        let x = Double(xc)*(xmax-xmin)/Double(xstep) + xmin
        print(escapes(cr: x, ci: y, it: iters), terminator: "")
    }
    print("")
}