##-
# Author: Brian Tiffin
# Dedicated to the public domain
#
# Date: August 2016
# Modified: 2016-10-03/23:10-0400
##+
#
# plot-function, trigonometric plotting, function from command line
#
$define points 300
$define xoff   4
$define base   64
$define yscale 60
$define xscale 100

invocable "sin", "cos", "tan"

# plot the given function, default to sine
procedure main(args)
    func := map(args[1]) | "sin"
    if not func == ("sin" | "cos" | "tan") then func := "sin" 

    # range of pixels for 300 points, y scaled at +/- 60, 4 pixel margins
    &window := open("Plotting", "g", "size=308,128", "canvas=hidden")

    # tan may cause runtime errors
    if func == "tan" then &error := 6

    color := "vivid orange"
    Fg(color)
    write(&window, "\n " || func)

    Fg("gray")
    DrawLine(2, 64, 306, 64)
    DrawLine(2, 2, 2, 126)
    DrawString(8, 10, "1", 8, 69, "0", 2, 126, "-1")
    DrawString(270, 76, left(points * 2 * &pi / 100, 6))

    Fg(color)
    every x := 0 to points do
        DrawPoint(xoff + x, base + yscale * func((2 * &pi * x) / xscale))

    WSync()
    WriteImage("../images/plot-" || func || ".png")
    close(&window)
end