Partial translation of perl tutorial

2024-12-23 17:41:41 +00:00 · 2020-05-27 23:42:46 +08:00 · 2020-05-27 23:42:46 +08:00 · ad5c9cde75
commit ad5c9cde75
parent 54c34420f8
1 changed files with 348 additions and 0 deletions
--- a/zh-tw/perl-tw.html.markdown
+++ b/zh-tw/perl-tw.html.markdown
@ -0,0 +1,348 @@
 ---
 name: perl
 category: language
 language: perl
 filename: learnperl-tw.pl
 contributors:
    - ["Korjavin Ivan", "http://github.com/korjavin"]
    - ["Dan Book", "http://github.com/Grinnz"]
 translators:
    - ["Kang-min Liu", "https://gugod.org"]
 lang: zh-tw
 ---
 Perl 5 為超過 25 年以來持續地發展，是具高度能力、豐富機能之程式語言。
 自大型主機至攜帶裝置，Perl 5 能於上百種平台上執行，既適於快速打造產品原型、亦合於大規模專案之發展。
 ```perl
 # 註解列皆以井字號為開頭
 #### 嚴謹度
 use strict;
 use warnings;
 # 所有的 perl 程式檔案都應當包含此兩列程式碼。在如變數名稱有拼寫錯誤之時，
 # strict 能使編譯過程失敗。而對於像是將未定義值接到字串中等等易犯之錯誤，
 # warnings 則能提供適當的警告訊息。
 #### Perl 變數與其型別
 # 變數的開頭皆為一印記（sigil），是為一符號，用以標示其型別。
 # 變數名稱唯有以字母或底線開頭，後接字母、數字、底線若干，方為有效。
 ### 在 Perl 語言中，主要的變數型別有三種：$純量、@陣列、%雜湊。
 ## 純量
 #  一個純量變數，只能裝一個值：
 my $animal = "camel";
 my $answer = 42;
 my $display = "You have $answer ${animal}s.\n";
 # 純量值可為字串、整數、浮點數。Perl 會自動地在需要之時進行轉換。
 # 以單引號括住的字串內容與其字面之值完全相同。而以雙引號括住的字串，其中則能內插變數
 # 與像是表示換列的 "\n" 這種控制碼。
 ## 陣列
 # 一個陣列，可以裝下很多值：
 my @animals = ("camel", "llama", "owl");
 my @numbers = (23, 42, 69);
 my @mixed   = ("camel", 42, 1.23);
 # 陣列元素的存取，需要角括號。前方的印記為 $ 符號，表示只取一個值。
 my $second = $animals[1];
 # The size of an array is retrieved by accessing the array in a scalar
 # context, such as assigning it to a scalar variable or using the
 # "scalar" operator.
 # 欲知陣列之大小，在純量語境之下使用陣列便可。例如，將陣列裝到一個純量變數中。
 # 又或者是使用 scalar 算符。
 my $num_animals = @animals;
 print "Number of numbers: ", scalar(@numbers), "\n";
 # 陣列也能夠被安插在雙引號字串之內。各內容元素間隔，預設是一個空白字符。
 print "We have these numbers: @numbers\n";
 # 雙引號字串中，若有像電子郵件地址的部分，會被視為是在內插某個陣列的內容物。
 # 請稍加留意。
 my @example = ('secret', 'array');
 my $oops_email = "foo@example.com"; # 'foosecret array.com'
 my $ok_email = 'foo@example.com';
 ## Hashes
 #   A hash represents a set of key/value pairs:
 my %fruit_color = ("apple", "red", "banana", "yellow");
 #  You can use whitespace and the "=>" operator to lay them out more
 #  nicely:
 my %fruit_color = (
  apple  => "red",
  banana => "yellow",
 );
 # Hash elements are accessed using curly braces, again with the $ sigil.
 my $color = $fruit_color{apple};
 # All of the keys or values that exist in a hash can be accessed using
 # the "keys" and "values" functions.
 my @fruits = keys %fruit_color;
 my @colors = values %fruit_color;
 # Scalars, arrays and hashes are documented more fully in perldata.
 # (perldoc perldata).
 #### References
 # More complex data types can be constructed using references, which
 # allow you to build arrays and hashes within arrays and hashes.
 my $array_ref = \@array;
 my $hash_ref = \%hash;
 my @array_of_arrays = (\@array1, \@array2, \@array3);
 # You can also create anonymous arrays or hashes, returning a reference:
 my $fruits = ["apple", "banana"];
 my $colors = {apple => "red", banana => "yellow"};
 # References can be dereferenced by prefixing the appropriate sigil.
 my @fruits_array = @$fruits;
 my %colors_hash = %$colors;
 # As a shortcut, the arrow operator can be used to dereference and
 # access a single value.
 my $first = $array_ref->[0];
 my $value = $hash_ref->{banana};
 # See perlreftut and perlref for more in-depth documentation on
 # references.
 #### Conditional and looping constructs
 # Perl has most of the usual conditional and looping constructs.
 if ($var) {
  ...
 } elsif ($var eq 'bar') {
  ...
 } else {
  ...
 }
 unless (condition) {
  ...
 }
 # This is provided as a more readable version of "if (!condition)"
 # the Perlish post-condition way
 print "Yow!" if $zippy;
 print "We have no bananas" unless $bananas;
 #  while
 while (condition) {
  ...
 }
 my $max = 5;
 # for loops and iteration
 for my $i (0 .. $max) {
  print "index is $i";
 }
 for my $element (@elements) {
  print $element;
 }
 map {print} @elements;
 # implicitly
 for (@elements) {
  print;
 }
 # iterating through a hash (for and foreach are equivalent)
 foreach my $key (keys %hash) {
  print $key, ': ', $hash{$key}, "\n";
 }
 # the Perlish post-condition way again
 print for @elements;
 # iterating through the keys and values of a referenced hash
 print $hash_ref->{$_} for keys %$hash_ref;
 #### Regular expressions
 # Perl's regular expression support is both broad and deep, and is the
 # subject of lengthy documentation in perlrequick, perlretut, and
 # elsewhere. However, in short:
 # Simple matching
 if (/foo/)       { ... }  # true if $_ contains "foo"
 if ($x =~ /foo/) { ... }  # true if $x contains "foo"
 # Simple substitution
 $x =~ s/foo/bar/;         # replaces foo with bar in $x
 $x =~ s/foo/bar/g;        # replaces ALL INSTANCES of foo with bar in $x
 #### Files and I/O
 # You can open a file for input or output using the "open()" function.
 # For reading:
 open(my $in,  "<",  "input.txt")  or die "Can't open input.txt: $!";
 # For writing (clears file if it exists):
 open(my $out, ">",  "output.txt") or die "Can't open output.txt: $!";
 # For writing (appends to end of file):
 open(my $log, ">>", "my.log")     or die "Can't open my.log: $!";
 # You can read from an open filehandle using the "<>" operator.  In
 # scalar context it reads a single line from the filehandle, and in list
 # context it reads the whole file in, assigning each line to an element
 # of the list:
 my $line  = <$in>;
 my @lines = <$in>;
 # You can write to an open filehandle using the standard "print"
 # function.
 print $out @lines;
 print $log $msg, "\n";
 #### Writing subroutines
 # Writing subroutines is easy:
 sub logger {
  my $logmessage = shift;
  open my $logfile, ">>", "my.log" or die "Could not open my.log: $!";
  print $logfile $logmessage;
 }
 # Now we can use the subroutine just as any other built-in function:
 logger("We have a logger subroutine!");
 #### Modules
 # A module is a set of Perl code, usually subroutines, which can be used
 # in other Perl code. It is usually stored in a file with the extension
 # .pm so that Perl can find it.
 package MyModule;
 use strict;
 use warnings;
 sub trim {
  my $string = shift;
  $string =~ s/^\s+//;
  $string =~ s/\s+$//;
  return $string;
 }
 1;
 # From elsewhere:
 use MyModule;
 MyModule::trim($string);
 # The Exporter module can help with making subroutines exportable, so
 # they can be used like this:
 use MyModule 'trim';
 trim($string);
 # Many Perl modules can be downloaded from CPAN (http://www.cpan.org/)
 # and provide a range of features to help you avoid reinventing the
 # wheel.  A number of popular modules like Exporter are included with
 # the Perl distribution itself. See perlmod for more details on modules
 # in Perl.
 #### Objects
 # Objects in Perl are just references that know which class (package)
 # they belong to, so that methods (subroutines) called on it can be
 # found there. The bless function is used in constructors (usually new)
 # to set this up. However, you never need to call it yourself if you use
 # a module like Moose or Moo (see below).
 package MyCounter;
 use strict;
 use warnings;
 sub new {
  my $class = shift;
  my $self = {count => 0};
  return bless $self, $class;
 }
 sub count {
  my $self = shift;
  return $self->{count};
 }
 sub increment {
  my $self = shift;
  $self->{count}++;
 }
 1;
 # Methods can be called on a class or object instance with the arrow
 # operator.
 use MyCounter;
 my $counter = MyCounter->new;
 print $counter->count, "\n"; # 0
 $counter->increment;
 print $counter->count, "\n"; # 1
 # The modules Moose and Moo from CPAN can help you set up your object
 # classes. They provide a constructor and simple syntax for declaring
 # attributes. This class can be used equivalently to the one above.
 package MyCounter;
 use Moo; # imports strict and warnings
 has 'count' => (is => 'rwp', default => 0, init_arg => undef);
 sub increment {
  my $self = shift;
  $self->_set_count($self->count + 1);
 }
 1;
 # Object-oriented programming is covered more thoroughly in perlootut,
 # and its low-level implementation in Perl is covered in perlobj.
 ```
 #### FAQ
 perlfaq contains questions and answers related to many common tasks, and often provides suggestions for good CPAN modules to use.
 #### Further Reading
 - [perl-tutorial](http://perl-tutorial.org/)
 - [Learn at www.perl.com](http://www.perl.org/learn.html)
 - [perldoc](http://perldoc.perl.org/)
 - and perl built-in : `perldoc perlintro`