class Lisp

# File lib/calculo/lisp.rb, line 8
def initialize(string, type)
        @string = string
        @type = type
        @array = parse(@string)
        @result = eval_lisp(@array)
end

# File lib/calculo/lisp.rb, line 43
def eval_lisp(array)
        length, l, r = innermost_pair(array)
        result = execute(array[l..r],type)

        if length > 2
                # Inserts the result in between the portions
                # of the array not including the portion just
                # used to calculate the result
                new_array = array[0..(l-1)] + [result] + array[(r+1)..-1]
                eval_lisp(new_array)

        elsif length == 2
                return result
        end
end

# File lib/calculo/lisp.rb, line 16
def execute(array,type)
        case type
        when 'lisp'
                array[2..-2].reduce(array[1].to_sym)
        when 'reverse-lisp' || 'reverse'
                array[1..-3].reverse.reduce(array[-2].to_sym)
        end
end

# File lib/calculo/lisp.rb, line 25
def innermost_pair(array)
        l_parens = []
        r_parens = []

        array.each_with_index do |item, index|

                if item == "("
                        l_parens.push(index)

                elsif item == ")"
                        r_parens.push(index)
                end
        end

        total_length = l_parens.length + r_parens.length
        return [total_length, l_parens[-1], r_parens[0]]
end