open Impact

let redLine(a, b ,m, xlen) = 
    let mutable x = a-xlen
    let mutable xend = a+xlen
    let mutable y = b-xlen*m
    while (x < xend) do
        dot(x,y) red
        x <- x + 0.5
        y <- y + m*0.5
    dot(a,b) black


clear()


let f(x) = 80.*exp(-(((x-100.)/50.)**2.))
//let f(x) = 80./(1.+exp(-(x-100.)/20.))
//let f(x) = 10.*(x*exp(-(x/20.)))
//let f(x) = (x-25.)*(x-40.)*(x-110.)*(x-160.)/80000.
let fprime(x,h) = (f(x+h) - f(x)) / h
x <- 0.0
while x < 200.0 do
    dot(x,f(x)) pink
    x <- x + 1.0

h <- 0.1
x <- 0.0
while (x < 200.0) do
    dot(x,fprime(x,h)*20.0) red
    //m <- fprime(x,h)
    //redLine(x,f(x),m,h*2.0)
    //dot(x,f(x)) black
    x <- x + 1.0