从Python迁移到Racket (正则表达式库和"Racket方式“)

Question

我正在尝试学习球拍，并在此过程中尝试重写一个Python过滤器。我的代码中有以下两个函数：

def dlv(text):
    """
    Returns True if the given text corresponds to the output of DLV
    and False otherwise.
    """
    return text.startswith("DLV") or \
           text.startswith("{") or \
           text.startswith("Best model")

def answer_sets(text):
    """
    Returns a list comprised of all of the answer sets in the given text.
    """
    if dlv(text):
        # In the case where we are processing the output of DLV, each
        # answer set is a comma-delimited sequence of literals enclosed
        # in {}
        regex = re.compile(r'\{(.*?)\}', re.MULTILINE)
    else:
        # Otherwise we assume that the answer sets were generated by
        # one of the Potassco solvers. In this case, each answer set
        # is presented as a comma-delimited sequence of literals,
        # terminated by a period, and prefixed by a string of the form
        # "Answer: #" where "#" denotes the number of the answer set.
        regex = re.compile(r'Answer: \d+\n(.*)', re.MULTILINE)
    return regex.findall(text)

据我所知，function中第一个函数的实现如下所示：

(define (dlv-input? text)
    (regexp-match? #rx"^DLV|^{|^Best model" text))

它看起来工作正常。在第二个函数的实现上，我目前提出了以下建议(首先)：

(define (answer-sets text)
    (cond
        [(dlv-input? text) (regexp-match* #rx"{(.*?)}" text)]))

这是不正确的，因为regexp-match*给出了一个匹配正则表达式的字符串列表，包括花括号。有人知道如何在Python实现中获得相同的行为吗？此外，任何关于如何使正则表达式“更好”的建议都将不胜感激。

Answer 1

你已经很接近了。您只需在regexp-match调用中添加#:match-select cadr：

(regexp-match* #rx"{(.*?)}" text #:match-select cadr)

默认情况下，#:match-select的值为car，它返回整个匹配的字符串。cadr选择第一组，caddr选择第二组，依此类推。有关更多详细信息，请参阅regexp-match* documentation。