?:，?！之间的区别和?=
我搜索了这些表达式的含义，但无法理解它们之间的确切区别.
I searched for the meaning of these expressions but couldn't understand the exact difference between them.
他们是这样说的:
-
?:匹配表达式，但不捕获它. -
?=匹配后缀，但将其从捕获中排除. -
?!如果没有后缀，则匹配.
-
?:Match expression but do not capture it. -
?=Match a suffix but exclude it from capture. -
?!Match if the suffix is absent.
我尝试在简单的RegEx中使用它们，并获得了相似的结果.
I tried using these in simple RegEx and got similar results for all.
例如:以下3个表达式给出的结果非常相似.
For example: the following 3 expressions give very similar results.
-
[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+(?!\.[a-zA-Z0-9]+)* -
[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+(?=\.[a-zA-Z0-9]+)* -
[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9]+)*
[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+(?!\.[a-zA-Z0-9]+)*[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+(?=\.[a-zA-Z0-9]+)*[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9]+)*
?=和?!之间的区别在于，前者要求给定表达式匹配，而后者则要求不 >匹配.例如，a(?=b)将匹配"ab"中的"a"，但不匹配"ac"中的"a".而a(?!b)将匹配"ac"中的"a"，但不匹配"ab"中的"a".
The difference between ?= and ?! is that the former requires the given expression to match and the latter requires it to not match. For example a(?=b) will match the "a" in "ab", but not the "a" in "ac". Whereas a(?!b) will match the "a" in "ac", but not the "a" in "ab".
?:和?=之间的区别在于，?=从整个匹配项中排除了表达式，而?:只是不创建捕获组.因此，例如a(?:b)将与"abc"中的"ab"匹配，而a(?=b)将仅与"abc"中的"a"匹配. a(b)将匹配"abc"中的"ab" ，并创建一个包含"b"的捕获.
The difference between ?: and ?= is that ?= excludes the expression from the entire match while ?: just doesn't create a capturing group. So for example a(?:b) will match the "ab" in "abc", while a(?=b) will only match the "a" in "abc". a(b) would match the "ab" in "abc" and create a capture containing the "b".