3 # This document is in the public domain.
5 # The purpose is to document by example some of the new Perl5 features.
6 # It also functions as a mini test suite; you can extracted the
7 # expected output using:
8 # perl -ne 'm/.*prints ``(.*)..$/ && print $1,"\n";'
9 # There are a couple of places that print out internal address so it's
10 # not perfect yet, those should be fixed.
12 # Thanks to the following for their input:
13 # Johan.Vromans@NL.net
14 # Daniel Faken <absinthe@viva.chem.washington.edu>
15 # Tom Christiansen <tchrist@wraeththu.cs.colorado.edu>
16 # Dean Roehrich <roehrich@ferrari.cray.com>
17 # Larry Wall <lwall@netlabs.com>
19 # TODO when I get perl5a6 to play with
20 # *foo = \&func; # replaces only function (etc)
21 # AUTOLOAD { ...; } # called if method not found
22 # goto &func; # goto's a function
23 # require FOOBAR; # loads FOOBAR.pm
26 # import()/@EXPORT/etc
30 sub samp1 { print $z,"\n"; }
31 sub samp2 { my($z) = "world"; &samp1; }
32 $z = "hello"; &samp2; # prints ``hello''
35 # for catching non-local variable references
37 my $x = shift; # local() would work also
38 package; # empty package
39 $main::count += $x; # this is ok.
40 # $y = 1; # compile time error
44 # works like comma (,); use for key/value pairs
45 # sometimes used to disambiguate the final expression in a block
46 # might someday supply warnings if you get out of sync
47 %foo = ( abc => foo );
48 print $foo{abc},"\n"; # prints ``foo''
51 # works like tick (') (use of ' is deprecated in perl5)
52 print $main::foo{abc},"\n"; # prints ``foo''
55 # Bless takes a reference and returns an "object"
56 $oref = bless \$scalar;
59 # dereferences an "object"
60 $x = { def => bar }; # $x is ref to anonymous hash
61 print $x->{def},"\n"; # prints ``bar''
63 # method derefs must be bless'ed
66 sub samp4 { my($this) = shift; print $this->{def},"\n"; }
67 sub samp5 { print "samp5: @_\n"; }
68 $main::y = bless $main::x; # $x is ref, $y is "object"
70 $y->samp4(); # prints ``bar''
72 # indirect object calls
73 samp5 $y arglist; # prints ``samp5: sample=HASH(0xa85e0) arglist''
75 # static method calls (often used for constructors, see below)
76 samp5 sample arglist; # prints ``samp5: sample arglist''
78 # function calls without &
79 sub samp6 { print "look ma\n"; }
80 samp6; # prints ``look ma''
83 # returns "object" type
86 $x = bless \$y; # returns "object" $x in "class" OBJ1
87 print ref $x,"\n"; # prints ``OBJ1''
90 # and non-references return undef.
92 print "non-ref\n" if !defined(ref $z); # prints ``non-ref''
94 # ref's to "builtins" return type
95 print ref \$ascalar,"\n"; # prints ``SCALAR''
96 print ref \@array,"\n"; # prints ``ARRAY''
97 print ref \%hash,"\n"; # prints ``HASH''
98 sub func { print shift,"\n"; }
99 print ref \&func,"\n"; # prints ``CODE''
100 print ref \\$scalar,"\n"; # prints ``REF''
103 # bind a variable to a package with magic functions:
104 # new, fetch, store, delete, firstkey, nextkey (XXX: others???)
105 # Usage: tie variable, PackageName, ARGLIST
108 sub new { print "NEW: @_\n"; my($class, $x) = @_; bless \$x }
109 sub fetch { print "fetch @_\n"; my($this) = @_; ${$this} }
110 sub store { print "store @_\n"; my($this, $x) = @_; ${$this} = $x }
111 sub DESTROY { print "DESTROY @_\n" }
113 tie $h, TIEPACK, "black_tie"; # prints ``NEW: TIEPACK black_tie''
114 print $h, "\n"; # prints ``fetch TIEPACK=SCALAR(0x882a0)''
115 # prints ``black_tie''
116 $h = 'bar'; # prints ``store TIEPACK=SCALAR(0x882a0) bar''
117 untie $h; # DESTROY (XXX: broken in perl5a5???)
119 # References and Anonymous data-structures
120 $sref = \$scalar; # $$sref is scalar
121 $aref = \@array; # @$aref is array
122 $href = \%hash; # %$href is hash table
123 $fref = \&func; # &$fref is function
124 $refref = \$fref; # ref to ref to function
125 &$$refref("call the function"); # prints ``call the function''
127 %hash = ( abc => foo ); # hash (just like perl4)
128 print $hash{abc},"\n"; # prints ``foo''
129 $ref = { abc => bar }; # reference to anon hash
130 print $ref->{abc},"\n"; # prints ``bar''
132 @ary = ( 0, 1, 2 ); # array (just like perl4)
133 print $ary[1],"\n"; # prints ``1''
134 $ref = [ 3, 4, 5 ]; # reference to anon array
135 print $ref->[1],"\n"; # prints ``4''
137 # Nested data-structures
138 @foo = ( 0, { name => foobar }, 2, 3 ); # $#foo == 3
139 $aref = [ 0, { name => foobar }, 2, 3 ]; # ref to anon array
140 $href = { # ref to hash of arrays
141 John => [ Mary, Pat, Blanch ],
142 Paul => [ Sally, Jill, Jane ],
143 Mark => [ Ann, Bob, Dawn ],
145 print $href->{Paul}->[0], "\n"; # prints ``Sally''
146 print $href->{Paul}[0],"\n"; # shorthand version, prints ``Sally''
148 # Multiple Inheritence (get rich quick :-)
150 package OBJ2; sub abc { print "abc\n"; }
151 package OBJ3; sub def { print "def\n"; }
152 package OBJ4; @ISA = ("OBJ2", "OBJ3");
153 $x = bless { foo => bar };
154 $x->abc; # prints ``abc''
155 $x->def; # prints ``def''
158 # Packages, Classes, Objects, Methods, Constructors, Destructors, etc.
159 # XXX: I'll add more explinations/samples about the above here
162 sub new { print "NEW: @_\n"; my($x) = "empty"; bless \$x }
163 sub DESTROY { print "DESTROY\n" }
164 sub output { my($this) = shift; print "value = $$this\n"; }
166 # Constructors are often written as static method calls:
167 $x = new OBJ5; # prints ``NEW: OBJ5''
168 $x->output; # prints ``value = empty''
169 # The destructor is responsible for calling any base class destructors.