Out of curiosity, I have a general question about the optional perl parameter in R funtions like grep. As the title says in the title, i'd like to know why and when one should use this option. Is it a general thing to do if possible?
出于好奇，我对grep等函数中的可选perl参数有一个一般性问题。正如标题所说，我想知道为什么和什么时候应该使用这个选项。如果可能的话，这是一种普遍的做法吗?
In addition to that I thought about the reason of such a parameter. Someone must have decided that this is a way to go and I wonder why.
除此之外，我还想到了这样一个参数的原因。一定有人认为这是一条路，我想知道为什么。
I am almost positive that someone of you knows an answer.
我几乎肯定你们中有人知道答案。
1 个解决方案
#1
3
Regular expressions come in multiple flavors. Different flavors have different features, supported syntax, or other obscure differences.
正则表达式有多种形式。不同的风味具有不同的特性、支持的语法或其他模糊的差异。
Perl is considered as one of the most feature-complete flavor, which led to the develomment of the PCRE (Perl-Compatible Regular Expressions) library, which allows the use of the Perl flavor in other languages. There are some other regex libraries which support Perl syntax to some extent.
Perl被认为是功能最完备的库之一，这导致了PCRE(与Perl兼容的正则表达式)库的开发，它允许在其他语言中使用Perl。还有一些其他的regex库在某种程度上支持Perl语法。
Contrast this with the default regex flavor used in R: POSIX ERE, which is one of the least feature-complete.
与R: POSIX ERE中使用的默认regex风格相比，它是最不完整的特性之一。
You can use this site to compare flavors.
你可以使用这个网站来比较口味。
#1
3
Regular expressions come in multiple flavors. Different flavors have different features, supported syntax, or other obscure differences.
正则表达式有多种形式。不同的风味具有不同的特性、支持的语法或其他模糊的差异。
Perl is considered as one of the most feature-complete flavor, which led to the develomment of the PCRE (Perl-Compatible Regular Expressions) library, which allows the use of the Perl flavor in other languages. There are some other regex libraries which support Perl syntax to some extent.
Perl被认为是功能最完备的库之一，这导致了PCRE(与Perl兼容的正则表达式)库的开发，它允许在其他语言中使用Perl。还有一些其他的regex库在某种程度上支持Perl语法。
Contrast this with the default regex flavor used in R: POSIX ERE, which is one of the least feature-complete.
与R: POSIX ERE中使用的默认regex风格相比，它是最不完整的特性之一。
You can use this site to compare flavors.
你可以使用这个网站来比较口味。