# install package:
#    julia -e 'using Pkg; Pkg.add("ForwardDiff"); Pkg.add("Plots"); Pkg.add("PyPlot")'
# run from Julia console:
# include("aziz-diff.jl")

using ForwardDiff: derivative
using Printf

# definition of the function in file aziz.jl in current directory
push!(LOAD_PATH,pwd()) # add current directory to module search path
using Aziz
#  alternative: you could
# include("aziz.jl")
#  but then you'll need to use Aziz.aziz everywhere, unless you define aziz = Aziz.aziz

r  = [0.01:0.5:10.0;]
V  = aziz.(r)
Vp = derivative.(aziz, r);

@printf("%15s %15s %30s\n","r","V(r)","V'(r)")
for (a,b,c) in zip(r,V,Vp)
    @printf("%15.5f %15.5f %30.20f\n",a,b,c)   
end

r0 = 7.61
println("\ncomparing numerical der=(f(r+h)-f(r))/h and present AD result at r=$r0:\n")
Vp0 = derivative.(aziz, r0);
h = 0.1
a0 = aziz(r0)
while h > 1.e-14
    global h
    der = (aziz(r0+h)-a0)/h
    @printf("h=%10.3e  der=%25.20f   AD = %25.20f   der-AD=%25.20f\n", h, der, Vp0, der-Vp0)
    h = 0.1*h
end

println("plotting...")
using Plots
pyplot() # pyplot backend
# more points for plotting
r  = [0.01:0.01:10.0;]
V  = aziz.(r)
Vp = derivative.(aziz, r);
p = plot(r,V,label="V(r)",ylims=(-20,20))
p = plot!(r,Vp,label="V'(r)") # update previous plot

# just to make the plot appear long enough to see it
display(p)
readline()