Julia Triple-Quoted String Literals Alignment

Gary Gong

3 minute read

很多程式語言基本上都會提供三個單或雙引號來支援區塊（block）字串，例如 Python 就有提供相關功能。然而在 Parsing 上，Julia 卻是有一套規則在運行（部分測試也與 Python 有不同的結果），以下舉一些測試範例，以及大略推測 Julia 是如何解析：

Ref:

Julia v1.0 Docs - Triple-Quoted String Literals

我是看了文件了，但是不知道是不是自己資質駑鈍看不懂他的英文在寫啥。

Stackoverflow - Does the first line of triple-quoted string impact identation?

Github Issue - Julia - Problem with parsing triple quoted strings

排版歸依

例 A：

julia> str = """
           Hello,
           world.
         """
"  Hello,\n  world.\n"

推測行為：

# 原始
str = """
    Hello,
    world.
  """
# 斷第一行
"""
    Hello,
    world.
  """
# 去除第一個新行字元 (Leading Newline)
"""    Hello,
    world.
  """
# 去除縮排，補上新行字元 (Newline)
"""    Hello,\n    world.\n  """
    (4)         (4)        (2)
# 縮共同最長起始空白 (2格)
"""  Hello,\n  world.\n"""
#最後變成
"  Hello,\n  world.\n"

例 B：

julia> str = """
           Hello,
           world.
          """
" Hello,\n world.\n"

推測行為：

# 原始
str = """
    Hello,
    world.
   """
# 斷第一行
str = 
"""
    Hello,
    world.
   """
# 去除第一個新行字元(Leading Newline)
"""    Hello,
    world.
   """
# 去除縮排，補上新行字元(Newline)
"""    Hello,\n    world.\n   """
    (4)         (4)        （3)
# 縮共同最長起始空白(3格)
""" Hello,\n world.\n"""
#最後變成
" Hello,\n world.\n"

例 C：

julia> str = """
           Hello,
           world.
           """
"Hello,\nworld.\n"

推測行為：

# 原始
str = """
    Hello,
    world.
    """
# 斷第一行
"""
    Hello,
    world.
    """
# 去除第一個新行字元(Leading Newline)
"""    Hello,
    world.
    """
# 去除縮排，補上新行字元(Newline)
"""    Hello,\n    world.\n    """
    (4)         (4)         (4)
# 縮共同最長起始空白(4格)
"""Hello,\nworld.\n"""
#最後變成
"Hello,\nworld.\n"

例 D：

julia> str =   """
                  Hello,
                 world.
                """
"  Hello,\n world.\n"

推測行為：

# 原始
str =   """
           Hello,
          world.
         """
# 斷第一行
"""
           Hello,
          world.
         """
# 去除第一個新行字元(Leading Newline)
"""           Hello,
          world.
         """
# 去除縮排，補上新行字元(Newline)
"""           Hello,\n          world.\n         """
空白:  (11)              (10)              (9)
# 縮共同最長起始空白(9格)
"""  Hello,\n world.\n"""
#最後變成
"  Hello,\n world.\n"

例 E：

julia> str =   """
                  Hello,
                 world.
           aa"""
"       Hello,\n      world.\naa"

推測行為：

# 原始
str =   """
           Hello,
          world.
    aa"""
# 斷第一行   
"""
           Hello,
          world.
    aa"""
# 去除第一個新行字元(Leading Newline)
"""           Hello,
          world.
    aa"""
# 去除縮排，補上新行字元(Newline)
"""           Hello,\n          world.\n    aa"""
空白:  (11)               (10)            (4)
# 縮共同最長起始空白(4格)
"""       Hello,\n      world.\naa"""
#最後變成
"       Hello,\n      world.\naa"

例 F：

julia> str =   """
       Hello,
        world.
            aa  """
"Hello,\n world.\n     aa  "

推測行為：

# 原始
str =   """
       Hello,
        world.
            aa  """
# 斷第一行   
"""
       Hello,
        world.
            aa  """
# 去除第一個新行字元(Leading Newline)
"""       Hello,
        world.
            aa  """
# 去除縮排，補上新行字元(Newline)
"""       Hello,\n        world.\n            aa  """
空白: (7)             (8)              (12)      ^(非起始空白)
# 縮共同最長起始空白(7格)
"""Hello,\n world.\n     aa  """
#最後變成
"Hello,\n world.\n     aa  "

例 G：

julia> str =   """
       Hello,
        world.
            aa
         """
"Hello,\n world.\n     aa\n  "

推測行為：

# 原始
str =   """
       Hello,
        world.
            aa
         """
# 斷第一行   
"""
       Hello,
        world.
            aa
         """
# 去除第一個新行字元(Leading Newline)
"""       Hello,
        world.
            aa
         """
# 去除縮排，補上新行字元(Newline)
"""       Hello,\n        world.\n            aa\n         """
空白: (7)             (8)               (12)          (9)
# 縮共同最長起始空白(7格)
"""Hello,\n world.\n     aa\n  """
#最後變成
"Hello,\n world.\n     aa\n  "

後記：

Julia 只接受 """..."""，不理你的'''...'''。

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