正则表达式匹配草率分数/混合数字

Question

我有一系列包含混合数字的文本（即：整个部分和一个小数部分）。问题是文本充满了人为编码的邋iness：

1. 整个部分可能存在也可能不存在（例如：“10”）
2. 小数部分可能存在也可能不存在（例如：“1/3”）
3. 这两个部分可以用空格和/或连字符分隔（例如：“10 1/3”，“10-1 / 3”，“10 - 1/3”）。
4. 分数本身在数字和斜线之间可能有也可能没有空格（例如：“1/3”，“1/3”，“1/3”）。
5. 在需要忽略的分数后面可能还有其他文字

我需要一个可以解析这些元素的正则表达式，这样我就可以从这个混乱中创建一个正确的数字。

Answer 1

这是一个正则表达式，它将处理我可以抛出的所有数据：

(\d++(?! */))? *-? *(?:(\d+) */ *(\d+))?.*$

这会将数字放入以下组中：

1. 混合数字的整个部分（如果存在）
2. 分子，如果分数退出
3. 分母，如果存在分数

此外，这里是RegexBuddy对元素的解释（在构建它时极大地帮助了我）：

Match the regular expression below and capture its match into backreference number 1 «(\d++(?! */))?»
   Between zero and one times, as many times as possible, giving back as needed (greedy) «?»
   Match a single digit 0..9 «\d++»
      Between one and unlimited times, as many times as possible, without giving back (possessive) «++»
   Assert that it is impossible to match the regex below starting at this position (negative lookahead) «(?! */)»
      Match the character “ ” literally « *»
         Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
      Match the character “/” literally «/»
Match the character “ ” literally « *»
   Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
Match the character “-” literally «-?»
   Between zero and one times, as many times as possible, giving back as needed (greedy) «?»
Match the character “ ” literally « *»
   Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
Match the regular expression below «(?:(\d+) */ *(\d+))?»
   Between zero and one times, as many times as possible, giving back as needed (greedy) «?»
   Match the regular expression below and capture its match into backreference number 2 «(\d+)»
      Match a single digit 0..9 «\d+»
         Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
   Match the character “ ” literally « *»
      Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
   Match the character “/” literally «/»
   Match the character “ ” literally « *»
      Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
   Match the regular expression below and capture its match into backreference number 3 «(\d+)»
      Match a single digit 0..9 «\d+»
         Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
Match any single character that is not a line break character «.*»
   Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
Assert position at the end of the string (or before the line break at the end of the string, if any) «$»

Answer 2

我认为可能更容易解决彼此分开的不同情况（完全混合，仅分数，仅数字）。例如：

sub parse_mixed {
  my($mixed) = @_;

  if($mixed =~ /^ *(\d+)[- ]+(\d+) *\/ *(\d)+(\D.*)?$/) {
    return $1+$2/$3;
  } elsif($mixed =~ /^ *(\d+) *\/ *(\d+)(\D.*)?$/) {
    return $1/$2;
  } elsif($mixed =~ /^ *(\d+)(\D.*)?$/) {
    return $1;
  }
}

print parse_mixed("10"), "\n";
print parse_mixed("1/3"), "\n";
print parse_mixed("1 / 3"), "\n";
print parse_mixed("10 1/3"), "\n";
print parse_mixed("10-1/3"), "\n";
print parse_mixed("10 - 1/3"), "\n";

Answer 3

如果您使用Perl 5.10，我就会这样写。

m{
  ^
  \s*       # skip leading spaces

  (?'whole'
   \d++
   (?! \s*[\/] )   # there should not be a slash immediately following a whole number
  )

  \s*

  (?:    # the rest should fail or succeed as a group

    -?        # ignore possible neg sign
    \s*

    (?'numerator'
     \d+
    )

    \s*
    [\/]
    \s*

    (?'denominator'
     \d+
    )
  )?
}x

然后您可以访问%+变量中的值，如下所示：

$+{whole};
$+{numerator};
$+{denominator};