Prefix notation, S-expression, Lisp expression

lisp's S-expression is a multi-layer nested tree structure, which is closer to Abstract Syntax Tree (AST).

Regular is difficult to parse S-expression without recursive grammar.

The following is a simple example in python. I have commented it and it should be easy to understand.

def parse_sexp(string):
    sexp = [[]]
    word = ''
    in_str = False #是否在读取字符串
    for char in string: # 遍历每个字符
        if char == '(' and not in_str: # 左括号
            sexp.append([])
        elif char == ')' and not in_str: # 右括号
            if word:
                sexp[-1].append(word)
                word = ''
            temp = sexp.pop()
            sexp[-1].append(tuple(temp)) # 形成嵌套
        elif char in ' \n\t' and not in_str: # 空白符
            if word:
                sexp[-1].append(word)
                word = ''
        elif char == '"': # 双引号,字符串起止的标记
            in_str = not in_str
        else:
            word += char # 不是以上的分隔符,就是个合法的标记
    return sexp[0]

>>> parse_sexp("(+ 5 (+ 3 5))")
[('+', '5', ('+', '3', '5'))]
>>> parse_sexp("(add (add 1 2) (mul 2 1) 2 )")
[('add', ('add', '1', '2'), ('mul', '2', '1'), '2')]

S-expression

Regular:

\(\s*\w+(\s+\d+)+\s*\)|\w+|\d+

Note that this regex has a Global parameter

If there is only one layer of nested (op arg...) in arg1, arg2, arg3, ... argn, you can use this method