Grep找到Perl数组中的项目 [英] Grep to find item in Perl array

问题描述

每次输入内容时，代码都会告诉我它存在。但我知道一些输入不存在。什么是错的？

 ＃！/ usr / bin / perl 
 
 @array =<> ;; 
 print输入你要匹配的单词\\\
; 
 chomp（$ match =< STDIN>）; 
 
 if（grep（$ match，@array））{
 printfound it\\\
; 
 
  

解决方案

grep需要评估为真或假以表明是否匹配。所以它应该是：

 ＃注意，grep返回一个列表，所以$匹配需要在括号内以获得
＃实际值，否则$匹配将只包含匹配数
 if（my（$ matched）= grep $ _eq $ match，@array）{
 print找到它：$匹配\\\
; 
 
 $ / code> 

如果您需要匹配很多不同的值，它可能也是值得您考虑将数据数据放入散列中，因为散列允许您高效地执行此操作，而无需

 ＃将数组转换为散列值，数组元素作为散列键，值为1 
 my％hash = map {$ _ => 1} @array; 
 
＃检查散列是否包含$ match 
 if（defined $ hash {$ match}）{
 printfound it\\\
; 
} 
  




Every time I input something the code always tells me that it exists. But I know some of the inputs do not exist. What is wrong?

#!/usr/bin/perl

@array = <>;
print "Enter the word you what to match\n";
chomp($match = <STDIN>);

if (grep($match, @array)) {
    print "found it\n";
}

解决方案

The first arg that you give to grep needs to evaluate as true or false to indicate whether there was a match. So it should be:

# note that grep returns a list, so $matched needs to be in brackets to get the 
# actual value, otherwise $matched will just contain the number of matches
if (my ($matched) = grep $_ eq $match, @array) {
    print "found it: $matched\n";
}

If you need to match on a lot of different values, it might also be worth for you to consider putting the array data into a hash, since hashes allow you to do this efficiently without having to iterate through the list.

# convert array to a hash with the array elements as the hash keys and the values are simply 1
my %hash = map {$_ => 1} @array;

# check if the hash contains $match
if (defined $hash{$match}) {
    print "found it\n";
}

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