Question

我正在为一个长期过时的文本编辑器的脚本语言实现一个解释器，我在让词法分析器正常工作方面遇到了一些麻烦。

以下是该语言存在问题的部分示例：

T
L /LOCATE ME/
C /LOCATE ME/CHANGED ME/ * *
C ;CHANGED ME;CHANGED ME AGAIN; 1 *

/个字符似乎引用字符串，并且在C - 类型语法中充当CHANGE（sed）命令的分隔符，尽管它允许任何字符字符作为分隔符。

我可能实现了大约一半最常用的命令，直到现在才使用parse_tokens(line.split())。这很快又很脏，但效果出奇的好。

为避免编写自己的词法分析器，我尝试了shlex。

除CHANGE个案例外，它的效果非常好：

import shlex

def shlex_test(cmd_str):
    lex = shlex.shlex(cmd_str)
    lex.quotes = '/'
    return list(lex)

print(shlex_test('L /spaced string/'))
# OK! gives: ['L', '/spaced string/']

print(shlex_test('C /spaced string/another string/ * *'))
# gives   : ['C', '/spaced string/', 'another', 'string/', '*', '*']
# desired : any format that doesn't split on a space between /'s

print(shlex_test('C ;a b;b a;'))
# gives   : ['C', ';', 'b', 'a', ';', 'a', 'b', ';']
# desired : same format as CHANGE command above

任何人都知道一种简单的方法来实现这一目标（使用shlex或其他方式）？

编辑：

如果有帮助，这里是帮助文件中给出的CHANGE命令语法：

'''
C [/stg1/stg2/ [n|n m]]

    The CHANGE command replaces the m-th occurrence of "stg1" with "stg2"
for the next n lines.  The default value for m and n is 1.'''

同样难以标记X和Y命令：

'''
X [/command/[command/[...]]n]
Y [/command/[command/[...]]n]

    The X and Y commands allow the execution of several commands contained
in one command.  To define an X or Y "command string", enter X (or Y)
followed by a space, then individual commands, each separated by a
delimiter (e.g. a period ".").  An unlimited number of commands may be
placed in the X or Y command string.  Once the command string has been
defined, entering X (or Y) followed optionally by a count n will execute
the defined command string n times.  If n is not specified, it will
default to 1.'''

Answer 1

问题可能是/不代表引号，而只是用于分隔。我猜第3个字符总是用来定义分隔符。此外，您不需要输出中的/或;，对吗？

我刚刚对L和C命令案例进行了拆分：

>>> def parse(cmd):
...     delim = cmd[2]
...     return cmd.split(delim)
...
>>> c_cmd = "C /LOCATE ME/CHANGED ME/ * *"
>>> parse(c_cmd)
['C ', 'LOCATE ME', 'CHANGED ME', ' * *']

>>> c_cmd2 = "C ;a b;b a;"
>>> parse(c_cmd2)
['C ', 'a b', 'b a', '']

>>> l_cmd = "L /spaced string/"
>>> parse(l_cmd)
['L ', 'spaced string', '']

对于可选的" * *"部分，您可以在最后一个列表元素上使用split(" ")。

>>> parse(c_cmd)[-1].split(" ")
['', '*', '*']

解析此脚本语言的最有效方法

1 个答案: