Can input a digit character and print the triangle

triangle.bf

>++++++[<+++++++>-]
++++++++++>
,

>++++++[<-------->-]<

[
  >+
  [
    >+>+<<-
  ]
  >>
  [
    <<+>>-
  ]
  <
  [
    <<<<.>>>>-
  ]
  <<<.
  >-
]

triangle_with comment.bf

>++++++[<+++++++>-]    # [0] = 42 == '*'
++++++++++>            # [1] = 10 == '\n'
,                      # [2] stdin        # accept '0'~'9'

>++++++[<-------->-]<  # [2] -= 48        # char - '0'

[                      # while([2]) {
  >+                   #   [3]++
  [                    #   while([3]) {   #
    >+>+<<-            #     [4]++,[5]++  #
  ]                    #     [3]--        #
  >>                   #   }              #  assign [4] from [3]
  [                    #   while([5]) {   #
    <<+>>-             #     [3]++        #
  ]                    #     [5]--        #
  <                    #   }              #
  [                    #   while([4]) {
    <<<<.              #     print([0])
    >>>>-              #     [4]--
  ]                    #   }
  <<<.                 #   print([1])
  >-                   #   [2]--
]                      # }