再帰呼び出しの様子を標準出力に表示

# 普通に再帰関数を定義
def gcd(a, b)
    b.zero? ? a.abs : gcd(b, a % b)
end

# 出力するよう指定
require './print_recursive_call'
extend PrintRecursiveCall
print_recursive_call :gcd

# 再帰関数を実行
gcd(1920, -1080)

gcd(1920, -1080)
|   gcd(-1080, -240)
|   |   gcd(-240, -120)
|   |   |   gcd(-120, 0)
|   |   |   #=> 120
|   |   #=> 120
|   #=> 120
#=> 120

module PrintRecursiveCall
    INDENT_STR = "|   "

    def print_recursive_call(*mtds)
        mtds.each do |mtd|
            mtd_org = :"#{mtd}_noprint"
            if respond_to? :alias_method, true
                alias_method mtd_org, mtd
            else # object main
                instance_eval "alias #{mtd_org} #{mtd}"
            end

            define_method mtd do |*args|
                @rec_depth ||= 0

                puts INDENT_STR * @rec_depth + "#{mtd}(#{args.map(&:inspect).join(", ")})"
                @rec_depth += 1
                result = send(mtd_org, *args)
                @rec_depth -= 1
                puts INDENT_STR * @rec_depth + "#=> #{result}"

                result
            end
        end
    end
end

require './print_recursive_call'

# 特定のクラスでのみ利用 → そのクラス内でextend
class Foo
    extend PrintRecursiveCall
    print_recursive_call :mtd1 # 定義済みのメソッド名
end

# 全てのクラスで利用 → Classクラスまたはその親クラスでinclude
Module.include PrintRecursiveCall
class Bar
    print_recursive_call :mtd2
end

# トップレベルでのみ利用 → extend
extend PrintRecursiveCall
print_recursive_call :mtd3

# どこでも利用 → Objectクラス相当でinclude
include PrintRecursiveCall
print_recursive_call :mtd4

def quick_sort(ary)
    return ary if ary.size <= 1

    pivot = ary.pop   # 毎回同じ結果になるよう、rand不使用
    ary_less_eq, ary_greater = ary.partition { |x| x <= pivot }
    quick_sort(ary_less_eq) + [pivot] + quick_sort(ary_greater)
end

require './print_recursive_call'
extend PrintRecursiveCall
print_recursive_call :quick_sort

ary = [5, 1, 3, 9, 7, 0, 4, 2, 8, 6]
quick_sort(ary)

quick_sort([5, 1, 3, 9, 7, 0, 4, 2, 8, 6])
|   quick_sort([5, 1, 3, 0, 4, 2])
|   |   quick_sort([1, 0])
|   |   |   quick_sort([])
|   |   |   #=> []
|   |   |   quick_sort([1])
|   |   |   #=> [1]
|   |   #=> [0, 1]
|   |   quick_sort([5, 3, 4])
|   |   |   quick_sort([3])
|   |   |   #=> [3]
|   |   |   quick_sort([5])
|   |   |   #=> [5]
|   |   #=> [3, 4, 5]
|   #=> [0, 1, 2, 3, 4, 5]
|   quick_sort([9, 7, 8])
|   |   quick_sort([7])
|   |   #=> [7]
|   |   quick_sort([9])
|   |   #=> [9]
|   #=> [7, 8, 9]
#=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

$table = [0, 1]
def fibonacci(n)
    $table[n] ||= fibonacci(n-2) + fibonacci(n-1)
end

require './print_recursive_call'
extend PrintRecursiveCall
print_recursive_call :fibonacci

fibonacci(5)
puts
fibonacci(5) # メモ済みの状態でもう1回

fibonacci(5)
|   fibonacci(3)
|   |   fibonacci(1)
|   |   #=> 1
|   |   fibonacci(2)
|   |   |   fibonacci(0)
|   |   |   #=> 0
|   |   |   fibonacci(1)
|   |   |   #=> 1
|   |   #=> 1
|   #=> 2
|   fibonacci(4)
|   |   fibonacci(2)
|   |   #=> 1
|   |   fibonacci(3)
|   |   #=> 2
|   #=> 3
#=> 5

fibonacci(5)
#=> 5

require './expr_parser'
require './print_recursive_call'

# 定義済みのクラスを開いて処理を追加
class ExprParser
    extend PrintRecursiveCall
    print_recursive_call :additive, :multitive, :primary, :decimal
end

ExprParser.new.parse("1+2*(3*(4+5)+6)*(7+8)+9")

additive(0)
|   multitive(0)
|   |   primary(0)
|   |   |   decimal(0)
|   |   |   #=> [1, 1]
|   |   #=> [1, 1]
|   #=> [1, 1]
|   multitive(2)
|   |   primary(2)
|   |   |   decimal(2)
|   |   |   #=> [3, 2]
|   |   #=> [3, 2]
|   |   primary(4)
|   |   |   decimal(4)
|   |   |   #=> [nil, nil]
|   |   |   additive(5)
|   |   |   |   multitive(5)
|   |   |   |   |   primary(5)
|   |   |   |   |   |   decimal(5)
|   |   |   |   |   |   #=> [6, 3]
|   |   |   |   |   #=> [6, 3]
|   |   |   |   |   primary(7)
|   |   |   |   |   |   decimal(7)
|   |   |   |   |   |   #=> [nil, nil]
|   |   |   |   |   |   additive(8)
|   |   |   |   |   |   |   multitive(8)
|   |   |   |   |   |   |   |   primary(8)
|   |   |   |   |   |   |   |   |   decimal(8)
|   |   |   |   |   |   |   |   |   #=> [9, 4]
|   |   |   |   |   |   |   |   #=> [9, 4]
|   |   |   |   |   |   |   #=> [9, 4]
|   |   |   |   |   |   |   multitive(10)
|   |   |   |   |   |   |   |   primary(10)
|   |   |   |   |   |   |   |   |   decimal(10)
|   |   |   |   |   |   |   |   |   #=> [11, 5]
|   |   |   |   |   |   |   |   #=> [11, 5]
|   |   |   |   |   |   |   #=> [11, 5]
|   |   |   |   |   |   #=> [11, 9]
|   |   |   |   |   #=> [12, 9]
|   |   |   |   #=> [12, 27]
|   |   |   |   multitive(13)
|   |   |   |   |   primary(13)
|   |   |   |   |   |   decimal(13)
|   |   |   |   |   |   #=> [14, 6]
|   |   |   |   |   #=> [14, 6]
|   |   |   |   #=> [14, 6]
|   |   |   #=> [14, 33]
|   |   #=> [15, 33]
|   |   primary(16)
|   |   |   decimal(16)
|   |   |   #=> [nil, nil]
|   |   |   additive(17)
|   |   |   |   multitive(17)
|   |   |   |   |   primary(17)
|   |   |   |   |   |   decimal(17)
|   |   |   |   |   |   #=> [18, 7]
|   |   |   |   |   #=> [18, 7]
|   |   |   |   #=> [18, 7]
|   |   |   |   multitive(19)
|   |   |   |   |   primary(19)
|   |   |   |   |   |   decimal(19)
|   |   |   |   |   |   #=> [20, 8]
|   |   |   |   |   #=> [20, 8]
|   |   |   |   #=> [20, 8]
|   |   |   #=> [20, 15]
|   |   #=> [21, 15]
|   #=> [21, 990]
|   multitive(22)
|   |   primary(22)
|   |   |   decimal(22)
|   |   |   #=> [23, 9]
|   |   #=> [23, 9]
|   #=> [23, 9]
#=> [23, 1000]