我正在努力开发一个相当快速的全文搜索。它将读取索引,理想情况下应该只在一个正则表达式中运行匹配。
因此,我需要一个只有在包含某些单词时匹配行的正则表达式。
E.g。对
my $txt="one two three four five\n".
"two three four\n".
"this is just a one two three test\n";
只应匹配第一行和第三行,因为第二行不包含单词“one”。
现在我可以在一段时间内浏览每一行()或使用多个正则表达式,但我需要我的解决方案才能快速。
这里的例子: http://www.regular-expressions.info/completelines.html (“查找包含或不包含某些单词的行”)
是我需要的。但是,我不能让它在Perl中工作。我尝试了很多,但它没有提出任何结果。
my $txt="one two three four five\ntwo three four\nthis is just a one two three test\n";
my @matches=($txt=~/^(?=.*?\bone\b)(?=.*?\btwo\b)(?=.*?\bthree\b).*$/gi);
print join("\n",@matches);
没有输出。
总结: 我需要一个正则表达式来匹配包含多个单词的行,并返回这些整行。
提前感谢您的帮助!我尝试了很多,但只是不让它发挥作用。
答案 0 :(得分:1)
默认情况下,^
和$
元字符仅匹配输入的开头和结尾。要让它们匹配行的开头和结尾,请启用m
(MULTI-LINE)标志:
my $txt="one two three four five\ntwo three four\nthis is just a one two three test\n";
my @matches=($txt=~/^(?=.*?\bone\b)(?=.*?\btwo\b)(?=.*?\bthree\b).*$/gim);
print join("\n",@matches);
产生
one two three four five
this is just a one two three test
但是,如果你真的想要一个快速搜索,如果你问我,那么正则表达式(有很多展望)是不可取的。
答案 1 :(得分:0)
<强>代码:
use 5.012;
use Benchmark qw(cmpthese);
use Data::Dump;
use once;
our $str = <<STR;
one thing
another two
three to go
no war
alone in the dark
war never changes
STR
our @words = qw(one war two);
cmpthese(100000, {
'regexp with o' => sub {
my @m;
my $words = join '|', @words;
@m = $str =~ /(?!.*?\b(?:$words)\b)^(.*)$/omg;
ONCE { say 'regexp with o:'; dd @m }
},
'regexp' => sub {
my @m;
@m = $str =~ /(?!.*?\b(?:@{ [ join '|', @words ] })\b)^(.*)$/mg;
ONCE { say 'regexp:'; dd @m }
},
'while' => sub {
my @m;
@m = grep $_ !~ /\b(?:@{ [ join '|',@words ] })\b/,(split /\n/,$str);
ONCE { say 'while:'; dd @m }
},
'while with o' => sub {
my @m;
my $words = join '|',@words;
@m = grep $_ !~ /\b(?:$words)\b/o,(split /\n/,$str);
ONCE { say 'while with o:'; dd @m }
}
})
<强>所得:
regexp:
("three to go", "alone in the dark")
regexp with o:
("three to go", "alone in the dark")
while:
("three to go", "alone in the dark")
while with o:
("three to go", "alone in the dark")
Rate regexp regexp with o while while with o
regexp 19736/s -- -2% -40% -60%
regexp with o 20133/s 2% -- -38% -59%
while 32733/s 66% 63% -- -33%
while with o 48948/s 148% 143% 50% --
<强>Сonclusion
因此,使用while的变体比使用regexp的变体更快.`