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分类: PERL

2013-06-06 10:55:09

接上文:
http://blog.chinaunix.net/blog/post/id/3560959.html

七、CODE EXAMPLES【代码示例】
Presented with little comment (these will get their own manpages someday) here are short 
code examples illustrating access of various types of data structures.


1. ARRAYS OF ARRAYS【数组的数组】
1.1 Declaration of an ARRAY OF ARRAYS
声明数组的数组:
 @AoA = (
        [ "fred", "barney" ],
        [ "george", "jane", "elroy" ],
        [ "homer", "marge", "bart" ],
      );


1.2 Generation of an ARRAY OF ARRAYS
生成:
 # reading from file
 while ( <> ) {
     push @AoA, [ split ];
 }
 # calling a function
 for $i ( 1 .. 10 ) {
     $AoA[$i] = [ somefunc($i) ];
 }
 # using temp vars
 for $i ( 1 .. 10 ) {
     @tmp = somefunc($i);
     $AoA[$i] = [ @tmp ];
 }
 # add to an existing row
 push @{ $AoA[0] }, "wilma", "betty";


1.3 Access and Printing of an ARRAY OF ARRAYS
访问和输出
 # one element
 $AoA[0][0] = "Fred";
 # another element
 $AoA[1][1] =~ s/(\w)/\u$1/;
 # print the whole thing with refs
 for $aref ( @AoA ) {
     print "\t [ @$aref ],\n";
 }
 # print the whole thing with indices
 for $i ( 0 .. $#AoA ) {
     print "\t [ @{$AoA[$i]} ],\n";
 }
 # print the whole thing one at a time
 for $i ( 0 .. $#AoA ) {
     for $j ( 0 .. $#{ $AoA[$i] } ) {
         print "elt $i $j is $AoA[$i][$j]\n";
     }
 }


2. HASHES OF ARRAYS【哈希表的元素为数组】
2.1 Declaration of a HASH OF ARRAYS
声明
 %HoA = (
        flintstones        => [ "fred", "barney" ],
        jetsons            => [ "george", "jane", "elroy" ],
        simpsons           => [ "homer", "marge", "bart" ],
      );

2.2 Generation of a HASH OF ARRAYS
生成
 # reading from file
 # flintstones: fred barney wilma dino
 while ( <> ) {
     next unless s/^(.*?):\s*//;
     $HoA{$1} = [ split ];
 }
 # reading from file; more temps
 # flintstones: fred barney wilma dino
 while ( $line = <> ) {
     ($who, $rest) = split /:\s*/, $line, 2;
     @fields = split ' ', $rest;
     $HoA{$who} = [ @fields ];
 }
 # calling a function that returns a list
 for $group ( "simpsons", "jetsons", "flintstones" ) {
     $HoA{$group} = [ get_family($group) ];
 }
 # likewise, but using temps
 for $group ( "simpsons", "jetsons", "flintstones" ) {
     @members = get_family($group);
     $HoA{$group} = [ @members ];
 }
 # append new members to an existing family
 push @{ $HoA{"flintstones"} }, "wilma", "betty";


2.3 Access and Printing of a HASH OF ARRAYS
访问
 # one element
 $HoA{flintstones}[0] = "Fred";
 # another element
 $HoA{simpsons}[1] =~ s/(\w)/\u$1/;
 # print the whole thing
 foreach $family ( keys %HoA ) {
     print "$family: @{ $HoA{$family} }\n"
 }
 # print the whole thing with indices
 foreach $family ( keys %HoA ) {
     print "family: ";
     foreach $i ( 0 .. $#{ $HoA{$family} } ) {
         print " $i = $HoA{$family}[$i]";
     }
     print "\n";
 }
 # print the whole thing sorted by number of members
 foreach $family ( sort { @{$HoA{$b}} @{$HoA{$a}} } keys %HoA ) {
     print "$family: @{ $HoA{$family} }\n"
 }
 # print the whole thing sorted by number of members and name
 foreach $family ( sort {
   @{$HoA{$b}} @{$HoA{$a}}
||
   $a cmp $b
   } keys %HoA )
 {
     print "$family: ", join(", ", sort @{ $HoA{$family} }), "\n";
 }


3. ARRAYS OF HASHES【数组的元素为哈希】
3.1 Declaration of an ARRAY OF HASHES
声明
 @AoH = (
        {
            Lead     => "fred",
            Friend   => "barney",
        },
        {
            Lead     => "george",
            Wife     => "jane",
            Son      => "elroy",
        },
        {
            Lead     => "homer",
            Wife     => "marge",
            Son      => "bart",
        }
  );


3.2 Generation of an ARRAY OF HASHES
生成
 # reading from file
 # format: LEAD=fred FRIEND=barney
 while ( <> ) {
     $rec = {};
     for $field ( split ) {
         ($key, $value) = split /=/, $field;
         $rec->{$key} = $value;
     }
     push @AoH, $rec;
 }
 # reading from file
 # format: LEAD=fred FRIEND=barney
 # no temp
 while ( <> ) {
     push @AoH, { split /[\s+=]/ };
 }
 # calling a function  that returns a key/value pair list, like
 # "lead","fred","daughter","pebbles"
 while ( %fields = getnextpairset() ) {
     push @AoH, { %fields };
 }
 # likewise, but using no temp vars
 while (<>) {
     push @AoH, { parsepairs($_) };
 }
 # add key/value to an element
 $AoH[0]{pet} = "dino";
 $AoH[2]{pet} = "santa's little helper";


3.3 Access and Printing of an ARRAY OF HASHES
访问
 # one element
 $AoH[0]{lead} = "fred";
 # another element
 $AoH[1]{lead} =~ s/(\w)/\u$1/;
 # print the whole thing with refs
 for $href ( @AoH ) {
     print "{ ";
     for $role ( keys %$href ) {
         print "$role=$href->{$role} ";
     }
     print "}\n";
 }
 # print the whole thing with indices
 for $i ( 0 .. $#AoH ) {
     print "$i is { ";
     for $role ( keys %{ $AoH[$i] } ) {
         print "$role=$AoH[$i]{$role} ";
     }
     print "}\n";
 }
 # print the whole thing one at a time
 for $i ( 0 .. $#AoH ) {
     for $role ( keys %{ $AoH[$i] } ) {
         print "elt $i $role is $AoH[$i]{$role}\n";
     }
 }


4. HASHES OF HASHES【哈希的哈希】
4.1 Declaration of a HASH OF HASHES
声明
 %HoH = (
        flintstones => {
           lead      => "fred",
           pal       => "barney",
        },
        jetsons     => {
           lead      => "george",
           wife      => "jane",
           "his boy" => "elroy",
        },
        simpsons    => {
          lead      => "homer",
          wife      => "marge",
          kid       => "bart",
        },
 );


4.2 Generation of a HASH OF HASHES
生成
 # reading from file
 # flintstones: lead=fred pal=barney wife=wilma pet=dino
 while ( <> ) {
     next unless s/^(.*?):\s*//;
     $who = $1;
     for $field ( split ) {
         ($key, $value) = split /=/, $field;
         $HoH{$who}{$key} = $value;
     }
 # reading from file; more temps
 while ( <> ) {
     next unless s/^(.*?):\s*//;
     $who = $1;
     $rec = {};
     $HoH{$who} = $rec;
     for $field ( split ) {
         ($key, $value) = split /=/, $field;
         $rec->{$key} = $value;
     }
 }
 # calling a function  that returns a key,value hash
 for $group ( "simpsons", "jetsons", "flintstones" ) {
     $HoH{$group} = { get_family($group) };
 }
 # likewise, but using temps
 for $group ( "simpsons", "jetsons", "flintstones" ) {
     %members = get_family($group);
     $HoH{$group} = { %members };
 }
 # append new members to an existing family
 %new_folks = (
     wife => "wilma",
     pet  => "dino",
 );
 for $what (keys %new_folks) {
     $HoH{flintstones}{$what} = $new_folks{$what};
 }


4.3 Access and Printing of a HASH OF HASHES
访问
 # one element
 $HoH{flintstones}{wife} = "wilma";
 # another element
 $HoH{simpsons}{lead} =~ s/(\w)/\u$1/;
 # print the whole thing
 foreach $family ( keys %HoH ) {
     print "$family: { ";
     for $role ( keys %{ $HoH{$family} } ) {
         print "$role=$HoH{$family}{$role} ";
     }
     print "}\n";
 }
 # print the whole thing  somewhat sorted
 foreach $family ( sort keys %HoH ) {
     print "$family: { ";
     for $role ( sort keys %{ $HoH{$family} } ) {
         print "$role=$HoH{$family}{$role} ";
     }
     print "}\n";
 }
 # print the whole thing sorted by number of members
 foreach $family ( sort { keys %{$HoH{$b}} keys %{$HoH{$a}} } keys %HoH ) {
     print "$family: { ";
     for $role ( sort keys %{ $HoH{$family} } ) {
         print "$role=$HoH{$family}{$role} ";
     }
     print "}\n";
 }
 # establish a sort order (rank) for each role
 $i = 0;
 for ( qw(lead wife son daughter pal pet) ) { $rank{$_} = ++$i }
 # now print the whole thing sorted by number of members
 foreach $family ( sort { keys %{ $HoH{$b} } keys %{ $HoH{$a} } } keys %HoH ) {
     print "$family: { ";
     # and print these according to rank order
     for $role ( sort { $rank{$a} $rank{$b} }  keys %{ $HoH{$family} } ) {
         print "$role=$HoH{$family}{$role} ";
     }
     print "}\n";
 }


5. MORE ELABORATE RECORDS【更复杂的记录】
5.1 Declaration of MORE ELABORATE RECORDS
声明
Here's a sample showing how to create and use a record whose fields are of many different sorts:
     $rec = {
         TEXT      => $string,
         SEQUENCE  => [ @old_values ],
         LOOKUP    => { %some_table },
         THATCODE  => \&some_function,
         THISCODE  => sub { $_[0] ** $_[1] },
         HANDLE    => \*STDOUT,
     };

     print $rec->{TEXT};
     print $rec->{SEQUENCE}[0];
     $last = pop @ { $rec->{SEQUENCE} };
     print $rec->{LOOKUP}{"key"};
     ($first_k, $first_v) = each %{ $rec->{LOOKUP} };
     $answer = $rec->{THATCODE}->($arg);
     $answer = $rec->{THISCODE}->($arg1, $arg2);

     # careful of extra block braces on fh ref
     print { $rec->{HANDLE} } "a string\n";
     use FileHandle;
     $rec->{HANDLE}->autoflush(1);
     $rec->{HANDLE}->print(" a string\n");


5.2 Declaration of a HASH OF COMPLEX RECORDS
定义
     %TV = (
        flintstones => {
            series   => "flintstones",
            nights   => [ qw(monday thursday friday) ],
            members  => [
                { name => "fred",    role => "lead", age  => 36, },
                { name => "wilma",   role => "wife", age  => 31, },
                { name => "pebbles", role => "kid",  age  =>  4, },
            ],
        },
        jetsons     => {
            series   => "jetsons",
            nights   => [ qw(wednesday saturday) ],
            members  => [
                { name => "george",  role => "lead", age  => 41, },
                { name => "jane",    role => "wife", age  => 39, },
                { name => "elroy",   role => "kid",  age  =>  9, },
            ],
         },
        simpsons    => {
            series   => "simpsons",
            nights   => [ qw(monday) ],
            members  => [
                { name => "homer", role => "lead", age  => 34, },
                { name => "marge", role => "wife", age => 37, },
                { name => "bart",  role => "kid",  age  =>  11, },
            ],
         },
      );


5.3 Generation of a HASH OF COMPLEX RECORDS
生成
     # reading from file
     # this is most easily done by having the file itself be
     # in the raw data format as shown above.  perl is happy
     # to parse complex data structures if declared as data, so
     # sometimes it's easiest to do that
     # here's a piece by piece build up
     $rec = {};
     $rec->{series} = "flintstones";
     $rec->{nights} = [ find_days() ];
     @members = ();
     # assume this file in field=value syntax
     while (<>) {
         %fields = split /[\s=]+/;
         push @members, { %fields };
     }
     $rec->{members} = [ @members ];
     # now remember the whole thing
     $TV{ $rec->{series} } = $rec;
     ###########################################################
     # now, you might want to make interesting extra fields that
     # include pointers back into the same data structure so if
     # change one piece, it changes everywhere, like for example
     # if you wanted a {kids} field that was a reference
     # to an array of the kids' records without having duplicate
     # records and thus update problems.
     ###########################################################
     foreach $family (keys %TV) {
         $rec = $TV{$family}; # temp pointer
         @kids = ();
         for $person ( @{ $rec->{members} } ) {
             if ($person->{role} =~ /kid|son|daughter/) {
                 push @kids, $person;
             }
         }
         # REMEMBER: $rec and $TV{$family} point to same data!!
         $rec->{kids} = [ @kids ];
     }
     # you copied the array, but the array itself contains pointers
     # to uncopied objects. this means that if you make bart get
     # older via
     $TV{simpsons}{kids}[0]{age}++;
     # then this would also change in
     print $TV{simpsons}{members}[2]{age};
     # because $TV{simpsons}{kids}[0] and $TV{simpsons}{members}[2]
     # both point to the same underlying anonymous hash table
     # print the whole thing
     foreach $family ( keys %TV ) {
         print "the $family";
         print " is on during @{ $TV{$family}{nights} }\n";
         print "its members are:\n";
         for $who ( @{ $TV{$family}{members} } ) {
             print " $who->{name} ($who->{role}), age $who->{age}\n";
         }
         print "it turns out that $TV{$family}{lead} has ";
         print scalar ( @{ $TV{$family}{kids} } ), " kids named ";
         print join (", ", map { $_->{name} } @{ $TV{$family}{kids} } );
         print "\n";
     }


八、Database Ties
You cannot easily tie a multilevel data structure (such as a hash of hashes) to a dbm file. 
The first problem is that all but GDBM and Berkeley DB have size limitations, but beyond that, 
you also have problems with how references are to be represented on disk. One experimental 
module that does partially attempt to address this need is the MLDBM module. Check your 
nearest CPAN site as described in perlmodlib for source code to MLDBM.
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