##-
# 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   154
$define base   164
$define yscale 60
$define xscale 100

invocable "asin", "acos", "atan"

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

    # range of pixels for 300 points, y scaled at +/- 60, 4 pixel margins
    &window := open("Plotting", "g", "size=308,168", "canvas=hidden")

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

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

    Fg("gray")
    DrawLine(2, base, 306, base)
    DrawLine(xoff, 2, xoff, 164)
    #DrawString(8, 10, "1.5+", 8, 69, "0", 2, 126, "-1.5-")
    DrawString(xscale / 2 + 2, 160, "-1.0")
    DrawString(points - (xscale / 2) - 2, 160, "1.0")

    Fg(color)
    step := 2.0 / points
    every x := -1.0 to 1.0 by step do {
        DrawPoint(xoff + (x * xscale), base - (yscale * func(x)))
    }
    WSync()
    WriteImage("../images/plot-" || func || ".png")
    close(&window)
end