1Scalar::Properties(3) User Contributed Perl DocumentationScalar::Properties(3)
2
6 Scalar::Properties - Run-time properties on scalar variables
7
9 version 1.100860
10
12 use Scalar::Properties;
13 my $val = 0->true;
14 if ($val && $val == 0) {
15 print "yup, its true alright...\n";
16 }
17 my @text = (
19 'hello world'->greeting(1),
20 'forget it',
21 'hi there'->greeting(1),
22 );
23 print grep { $_->is_greeting } @text;
24 my $l = 'hello world'->length;
26
28 Scalar::Properties attempts to make Perl more object-oriented by taking
29 an idea from Ruby: Everything you manipulate is an object, and the
30 results of those manipulations are objects themselves.
31 'hello world'->length
33 (-1234)->abs
34 "oh my god, it's full of properties"->index('g')
35 The first example asks a string to calculate its length. The second
37 example asks a number to calculate its absolute value. And the third
38 example asks a string to find the index of the letter 'g'.
39 Using this module you can have run-time properties on initialized
41 scalar variables and literal values. The word 'properties' is used in
42 the Perl 6 sense: out-of-band data, little sticky notes that are
43 attached to the value. While attributes (as in Perl 5's attribute
44 pragma, and see the "Attribute::*" family of modules) are handled at
45 compile-time, properties are handled at run-time.
46 Internally properties are implemented by making their values into
48 objects with overloaded operators. The actual properties are then
49 simply hash entries.
50 Most properties are simply notes you attach to the value, but some may
52 have deeper meaning. For example, the "true" and "false" properties
53 plays a role in boolean context, as the first example of the Synopsis
54 shows.
55 Properties can also be propagated between values. For details, see the
57 EXPORTS section below. Here is an example why this might be desirable:
58 pass_on('approximate');
60 my $pi = 3->approximate(1);
61 my $circ = 2 * $rad * $pi;
62 # now $circ->approximate indicates that this value was derived
64 # from approximate values
65 Please don't use properties whose name start with an underscore; these
67 are reserved for internal use.
68 You can set and query properties like this:
70 "$var->myprop(1)"
72 sets the property to a true value.
73 "$var->myprop(0)"
75 sets the property to a false value. Note that this doesn't delete
76 the property (to do so, use the "del_props" method described
77 below).
78 "$var->is_myprop", "$var->has_myprop"
80 returns a true value if the property is set (i.e., defined and has
81 a true value). The two alternate interfaces are provided to make
82 querying attributes sound more natural. For example:
83 $foo->is_approximate;
85 $bar->has_history;
86 Values thus made into objects also expose various utility methods. All
88 of those methods (unless noted otherwise) return the result as an
89 overloaded value ready to take properties and method calls itself, and
90 don't modify the original value.
91
93 get_props
94 Get a list of names of the value's properties.
95 del_props(LIST)
97 Deletes one or more properties from the value. This is different than
98 setting the property value to zero.
99 del_all_props
101 Deletes all of the value's properties.
102 plus(EXPR)
104 Returns the value that is the sum of the value whose method has been
105 called and the argument value. This method also overloads addition, so:
106 $a = 7 + 2;
108 $a = 7->plus(2); # the same
109 minus(EXPR)
111 Returns the value that is the the value whose method has been called
112 minus the argument value. This method also overloads subtraction.
113 times(EXPR)
115 Returns the value that is the the value whose method has been called
116 times the argument value. This method also overloads multiplication.
117 divide(EXPR)
119 Returns the value that is the the value whose method has been called
120 divided by the argument value. This method also overloads division.
121 modulo(EXPR)
123 Returns the value that is the the value whose method has been called
124 modulo the argument value. This method also overloads the modulo
125 operator.
126 exp(EXPR)
128 Returns the value that is the the value whose method has been called
129 powered by the argument value. This method also overloads the
130 exponentiation operator.
131 abs
133 Returns the absolute of the value.
134 zero
136 Returns a boolean value indicating whether the value is equal to 0.
137 length
139 Returns the result of the built-in "length" function applied to the
140 value.
141 size
143 Same as length().
144 reverse
146 Returns the reverse string of the value.
147 uc
149 Returns the result of the built-in function uc() applied to the value.
150 ucfirst
152 Returns the result of the built-in function ucfirst() applied to the
153 value.
154 lc
156 Returns the result of the built-in function lc() applied to the value.
157 lcfirst
159 Returns the result of the built-in function lcfirst() applied to the
160 value.
161 hex
163 Returns the result of the built-in function hex() applied to the value.
164 oct
166 Returns the result of the built-in function oct() applied to the value.
167 concat(EXPR)
169 Returns the result of the argument expression appended to the value.
170 append(EXPR)
172 Same as concat(EXPR).
173 swapcase
175 Returns a version of the value with every character's case reversed,
176 i.e. a lowercase character becomes uppercase and vice versa.
177 split /PATTERN/, LIMIT
179 Returns a list of overloaded values that is the result of splitting
180 (according to the built-in "split" function) the value along the
181 pattern, into a number of values up to the limit.
182 numcmp(EXPR)
184 Returns the (overloaded) value of the numerical three-way comparison.
185 This method also overloads the "<=>" operator.
186 cmp(EXPR)
188 Returns the (overloaded) value of the alphabetical three-way
189 comparison. This method also overloads the "cmp" operator.
190 eq(EXPR)
192 Return the (overloaded) boolean value of the "eq" string comparison.
193 This method also overloads that operators.
194 ne(EXPR)
196 Return the (overloaded) boolean value of the "ne" string comparison.
197 This method also overloads that operators.
198 lt(EXPR)
200 Return the (overloaded) boolean value of the "lt" string comparison.
201 This method also overloads that operators.
202 gt(EXPR)
204 Return the (overloaded) boolean value of the "gt" string comparison.
205 This method also overloads that operators.
206 le(EXPR)
208 Return the (overloaded) boolean value of the "le" string comparison.
209 This method also overloads that operators.
210 ge(EXPR)
212 Return the (overloaded) boolean value of the "ge" string comparison.
213 This method also overloads that operators.
214 eqi
216 Same as eq(), but is case-insensitive.
217 nei>
219 Same as ne(), but is case-insensitive.
220 lti
222 Same as lt(), but is case-insensitive.
223 gti
225 Same as gt(), but is case-insensitive.
226 lei
228 Same as le(), but is case-insensitive.
229 gei
231 Same as ge(), but is case-insensitive.
232 is_true
234 Returns whether the (overloaded) boolean status of the value is true.
235 is_false
237 Returns whether the (overloaded) boolean status of the value is false.
238 create
240 FIXME
241 del_prop
243 FIXME
244 do_downto
246 FIXME
247 do_downto_step
249 FIXME
250 do_upto
252 FIXME
253 do_upto_step
255 FIXME
256 false
258 FIXME
259 gen_meth
261 FIXME
262 handle
264 FIXME
265 times_do
267 FIXME
268 true
270 FIXME
271 value
273 FIXME
274
276 pass_on(LIST)
277 Sets (replaces) the list of properties that are passed on. There is
278 only one such list for the whole mechanism. The whole property
279 interface is experimental, but this one in particular is likely to
280 change in the future. This function is exported automatically.
281 passed_on(STRING)
283 Tests whether a property is passed on and returns a boolean value. This
284 function is exported automatically.
285 get_pass_on
287 Returns a list of names of properties that are passed on. This function
288 is exported automatically.
289
291 See perlmodinstall for information and options on installing Perl
292 modules.
293
295 No bugs have been reported.
296 Please report any bugs or feature requests through the web interface at
298 <http://rt.cpan.org/Public/Dist/Display.html?Name=Scalar-Properties>.
299
301 The latest version of this module is available from the Comprehensive
302 Perl Archive Network (CPAN). Visit <http://www.perl.com/CPAN/> to find
303 a CPAN site near you, or see
304 <http://search.cpan.org/dist/Scalar-Properties/>.
305 The development version lives at
307 <http://github.com/hanekomu/Scalar-Properties/>. Instead of sending
308 patches, please fork this project using the standard git and github
309 infrastructure.
310
312 Marcel Gruenauer <marcel@cpan.org>
313
315 This software is copyright (c) 2001 by Marcel Gruenauer.
316 This is free software; you can redistribute it and/or modify it under
318 the same terms as the Perl 5 programming language system itself.
319perl v5.36.0 2023-01-20 Scalar::Properties(3)