# подгружаются основные определения
require_relative './task16-math'

class Pi < Number
  PI = Math::PI
end

class Sin < MathExpression
  def initialize(e = Number.new(1))
    @e = e
  end

  def eval env
    e = @e.eval env
    e.evalExp
  end

  def derivative var
    e = @e.derivative var
    cosinus = Cos.new(@e)
    e.multiply cosinus
  end

  def to_s
    "sin(#{@e.to_s})"
  end

end

class Cos < MathExpression
  def initialize(e = Number.new(1))
    @e = e
  end

  def eval env
    e = @e.eval env
    e.evalExp
  end

  def derivative var
    e = @e.derivative var
    minus_sinus = Negate(Sin.new(@e)).new
    e.multiply minus_sinus
  end

  def to_s
    "cos(#{@e.to_s})"
  end

end



# ПРИМЕРЫ

puts(Derivative.new(Cos.new(Variable.new("y")), "y"))


puts(Derivative.new(
        Multiply.new(
          Add.new(
            Add.new(
              Multiply.new(Number.new(2),
                           Variable.new("x")),
              Multiply.new(Number.new(3),
                           Variable.new("y"))),
            Negate.new(Variable.new("z"))),
          Add.new(Number.new(5),
                  Variable.new("x"))),
        "x"))

# puts(Let.new("a", Multiply.new(Number.new(2),
#                                Variable.new("x")),        # a = 2x
#        Let.new("b", Multiply.new(Number.new(3),
#                                  Variable.new("y")),      # b = 3y
#          Let.new("e", Add.new(Variable.new("a"),
#                               Variable.new("b")),         # e = a + b
#             Multiply.new(Multiply.new(Variable.new("e"),
#                                       Variable.new("e")),
#                          Variable.new("e"))))))

# puts(Let.new("a", Multiply.new(Number.new(2),
#                                Variable.new("x")),   # a = 2x
#        Let.new("b", Multiply.new(Number.new(3),
#                                  Variable.new("y")), # b = 3y
#          Let.new("cube",                             # cube(e) = e * e * e
#                  MyFunc.new(nil, "e",
#                    Multiply.new(Multiply.new(Variable.new("e"),
#                                              Variable.new("e")),
#                                 Variable.new("e"))),
#            # вычисление cube(a + b) + cube(b)
#            Add.new(Call.new(Variable.new("cube"),        # вызов cube(a + b)
#                             Add.new(Variable.new("a"),
#                                     Variable.new("b"))),
#                    Call.new(Variable.new("cube"),        # вызов cube(b)
#                             Variable.new("b")))))))

# # вычисление выражений
# puts(Derivative.new(
#         Multiply.new(
#           Add.new(
#             Add.new(
#               Multiply.new(Number.new(2),
#                            Variable.new("x")),
#               Multiply.new(Number.new(3),
#                            Variable.new("y"))),
#             Negate.new(Variable.new("z"))),
#           Add.new(Number.new(5),
#                   Variable.new("x"))),
#         "x").eval_exp)

# puts(Let.new("a", Multiply.new(Number.new(2),
#                                Variable.new("x")),        # a = 2x
#        Let.new("b", Multiply.new(Number.new(3),
#                                  Variable.new("y")),      # b = 3y
#          Let.new("e", Add.new(Variable.new("a"),
#                               Variable.new("b")),         # e = a + b
#             Multiply.new(Multiply.new(Variable.new("e"),
#                                       Variable.new("e")),
#                          Variable.new("e"))))).eval_exp)

# puts(Let.new("a", Multiply.new(Number.new(2),
#                                Variable.new("x")),   # a = 2x
#        Let.new("b", Multiply.new(Number.new(3),
#                                  Variable.new("y")), # b = 3y
#          Let.new("cube",                             # cube(e) = e * e * e
#                  MyFunc.new(nil, "e",
#                    Multiply.new(Multiply.new(Variable.new("e"),
#                                              Variable.new("e")),
#                                 Variable.new("e"))),
#            # вычисление cube(a + b) + cube(b)
#            Add.new(Call.new(Variable.new("cube"),        # вызов cube(a + b)
#                             Add.new(Variable.new("a"),
#                                     Variable.new("b"))),
#                    Call.new(Variable.new("cube"),        # вызов cube(b)
#                             Variable.new("b")))))).eval_exp)