perl字符串与排序

 

 在字符串内用index

my $stuff = 'Howdy world!';
my $where = index($stuff,'wor');
print $where;   #  6

my $stuff = 'Howdy world!';
my $where1 = index($stuff,'w');           #2
my $where2 = index($stuff,'w',$where1+1); #6
my $where3 = index($stuff,'w',$where2+1); #-1

在字符串内用 rindex 搜所
my $last_slash = rindex("/etc/password",'/');   #4

my $fred = 'Yabba dabba doo!';
my $where1 = rindex($fred,'abba');             #7
my $where2 = rindex($fred,'abba',$where1-1);   #1
my $where3 = rindex($fred,'abba',$where2-1);   #-1

用substr处理子串
$part = substr($string,$initial_position,$length);

my $mineral = substr('Fred J. Plintstone',8,5);   #Plint
my $rock = substr 'Fred J. Plintstone',13,100;    #stone

my $string = 'Hello, world!';
substr($string ,0,5) = 'Goodby';   #Goodby, world!

substr和index 一起使用
my $long = 'some very very long string';
my $lin = index($long,'l');                   #15
my $right = substr($long,index($long,'l'));   #long string




mmy $string = 'dkfkkakdfredddddd';
substr($string,-13) =~ s/fred/barney/g;   #dkfkkakdbarneyddddd
















高级排序
   sub by_number {
      if ($a<$b) {-1} elsif ($a>$b){ 1 } else {0}
      }
   my @some_numbers = qw /3 4 6 1 2 9/;         # 3 4 6 1 2 9
   my @result = sort by_number @some_numbers;   # 123469

   sub by_number {$a <=> $b}
   my @some_numbers = qw /3 4 6 1 2 9/;
   my @result = sort by_number @some_numbers;


按哈希值排序
my %score = ('bareny' => 195,'fred' => 205,'dino' => 30,'bamm-bamm' => 195);
my @winners = sort by_score keys %score;
sub by_score {
   $score{$b} <=> $score{a}
}
print "@winners";  #fred bamm-bamm dino bareny

哈希值查找Fred
my $flag = 0;
foreach my $key(keys %name) {
   next unless $key =~ /Fred/;
   $flag = $key;
   last;
}