++Diary++

2003年10月30日の日記

Perl覚え書き
■Creating References

1. You can create areference to any named variable or subroutine with a backslash.
  $scalarref = \$foo;
  $arrayref = \@ARGV;
  $hashref = \%ENV;
  $coderef = \&handler;
  $globref = \*STDOUT;

2. You can create areference to an anonymous array with square brackets.
  $arrayref = [1,2,['a','b','c','d']];

3. You can create areference to an anonymous hash with braces.
  $hashref = {'Adam' => 'Eve','Clyde' => $bonnie,'Antony' => 'Cleo' . 'patra',};

4. You can create areference to an anonymous subroutine by using sub without a subroutine name.
  $coderef = sub{print "Boink!\n"}; #&$$coderef prints "Boink!"

5. References to filehandles or directory handles can be created by referring the typeglob of the same name.
  &splutter(\*STDOUT);
  Sub splutter {
   my $fh = shift;
   print $fh "..........\n";
  }

6. References can be created by dereferencing them.

■Dereferencing References

1. Using a Variable as a Variable Name
  $bar = $$scalarref;

  push (@$arrayref, $filename);
  $$arrayref[0] = "January";
  @$arrayref[4..6] = qw/May June July/;

  %$hashref = (KEY => "RING", BIRD => "SING");
  $$hashref{KEY} = "VALUE";
  @$hashref{"KEY1","KEY2"} = ("VAL1", "VAL2");

  &$coderef(1,2,3);

2. Using a BLOCK as a Variable Name
  $bar = ${$scalarref};

  push (@{$arrayref}, $filename);
  ${$arrayref}[0] = "January";
  @{$arrayref}[4..6] = qw/May June July/;

  %{$hashref} = (KEY => "RING", BIRD => "SING");
  ${$hashref}{KEY} = "VALUE";
  @{$hashref}{"KEY1","KEY2"} = ("VAL1", "VAL2");

  &{$coderef}(1,2,3);

3. Using the Arrow Operator
  $$arrayref[0] = "January";
  ${$arrayref}[0] = "January";
  $arrayref->[0] = "January";
  (上記のどの書き方でもOK)

  &$coderef(1,2,3);
  &{$coderef}(1,2,3);
  $coderef->(1,2,3);
  (上記のどの書き方でもOK)

  $listref->[2][2] = "hello";
  $$listref[2][2] = "hello";
  (上記のどの書き方でもOK)

■Array of Arrays
※以下はすべて同じ

for $i (1..10) {
 @array = somefunc ($i);
 $AoA[$i] = [@array];
}

for $i (1..10) {
 @array = somefunc ($i);
 @{$AoA[$i]} = @array;
}

for $i (1..10) {
 my @array = somefunc ($i);
 $AoA[$i] = \@array;
}

for $i (1..10) {
 $AoA[$i] = [somefunc ($i)];
}

■Hash of Arrays

for $group ("simpsons", "jetsons","flintstones") {
 $HoA{$group} = [get_famly($group)];
}

$HoA{$group}[1] =~ s/(\w)/\u$1/; #最初の文字を大文字に

for $family (sort {@{$HaA{$b}} <=> @{$HaA{$a}}} keys %HoA) {
 print "$family: ", join(",", sort @{$HaA{$family}}), "\n";
} #各Arrayの要素数で、Hashのキーを多い方からソートして、キーと要素(アスキー順にソートしたもの)を順にプリント

■Hash of Hashes

for $family (sort {keys %{$HaH{$b}} <=> keys %{$HaH{$a}}} keys %HoH) {
 print "$family: ";
 for $role (sort keys %{$HaH{$family}}) {
  print "$role=$HaH{$family}{$role}";
 }
 print "\n";
} #各Hashの要素数(キーの数)で、Hashのキーを多い方からソートして、キーと要素(アスキー順にソートしたもの)を順にプリント
2003年10月30日(木)   No.47

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