Derive the provided function for x or for a specific value

derive.jl

# Evaluate a derivative of a single-variable function
# Assume last argument is value/var and all others are function
# Example:
# $ julia derive.jl x^2 + x + 1 1
# > derivative at 1:
# > 2.999999999960656
# $ julia derive.jl x^2 + x + 1 x
# > derivative:
# > 2 * 1 * x ^ (2 - 1) + 1
using Calculus

is_symbolic_derivative = (match(r"\d+", ARGS[end]) === nothing)
if is_symbolic_derivative
  polynomial = join(ARGS[1:end-1]) 
  result = differentiate(polynomial, ARGS[end])
  println("derivative:\n", result)
else
  poly_str = replace(join(ARGS[1:end-1]), r"[A-Za-z]" => "x") 
  polynomial = eval(Meta.parse(string("x->", poly_str)))
  at_value = parse(Int64, ARGS[end])
  result = derivative(polynomial, at_value)
  println("derivative at ", ARGS[end], ":\n",  result)
end