[新手] 请问一个正则表达式的问题
请问Regexp.union方法中rdoc的解释中：c:\rb>ri Regexp.union---------------------------------------------------------- Regexp::union Regexp.union(*) => new_str------------------------------------------------------------------------ Return a +Regexp+ object that is the union of the given _pattern_s, i.e., will match any of its parts. The _pattern_s can be Regexp objects, in which case their options will be preserved, or Strings. If no arguments are given, returns +/(?!)/+. Regexp.union #=> /(?!)/ Regexp.union("penzance") #=> /penzance/ Regexp.union("skiing", "sledding") #=> /skiing|sledding/ Regexp.union(/dogs/, /cats/i) #=> /(?-mix:dogs)|(?i-mx:cats)/
里面的?!是什么意思，我看书上说是“传递给raise的异常对象”，在这里它指什么？能举个小例子吗？
还有/(?-mix:dogs)|(?i-mx:cats)/中的？-mix和？i-mx是什么意思？您是通过什么资料查到的？谢谢
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