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
150 value.
151 ucfirst
153 Returns the result of the built-in function "ucfirst()" applied to the
154 value.
155 lc
157 Returns the result of the built-in function "lc()" applied to the
158 value.
159 lcfirst
161 Returns the result of the built-in function "lcfirst()" applied to the
162 value.
163 hex
165 Returns the result of the built-in function "hex()" applied to the
166 value.
167 oct
169 Returns the result of the built-in function "oct()" applied to the
170 value.
171 concat(EXPR)
173 Returns the result of the argument expression appended to the value.
174 append(EXPR)
176 Same as "concat(EXPR)".
177 swapcase
179 Returns a version of the value with every character's case reversed,
180 i.e. a lowercase character becomes uppercase and vice versa.
181 split /PATTERN/, LIMIT
183 Returns a list of overloaded values that is the result of splitting
184 (according to the built-in "split" function) the value along the
185 pattern, into a number of values up to the limit.
186 numcmp(EXPR)
188 Returns the (overloaded) value of the numerical three-way comparison.
189 This method also overloads the "<=>" operator.
190 cmp(EXPR)
192 Returns the (overloaded) value of the alphabetical three-way
193 comparison. This method also overloads the "cmp" operator.
194 eq(EXPR)
196 Return the (overloaded) boolean value of the "eq" string comparison.
197 This method also overloads that operators.
198 ne(EXPR)
200 Return the (overloaded) boolean value of the "ne" string comparison.
201 This method also overloads that operators.
202 lt(EXPR)
204 Return the (overloaded) boolean value of the "lt" string comparison.
205 This method also overloads that operators.
206 gt(EXPR)
208 Return the (overloaded) boolean value of the "gt" string comparison.
209 This method also overloads that operators.
210 le(EXPR)
212 Return the (overloaded) boolean value of the "le" string comparison.
213 This method also overloads that operators.
214 ge(EXPR)
216 Return the (overloaded) boolean value of the "ge" string comparison.
217 This method also overloads that operators.
218 eqi
220 Same as "eq()", but is case-insensitive.
221 nei>
223 Same as "ne()", but is case-insensitive.
224 lti
226 Same as "lt()", but is case-insensitive.
227 gti
229 Same as "gt()", but is case-insensitive.
230 lei
232 Same as "le()", but is case-insensitive.
233 gei
235 Same as "ge()", but is case-insensitive.
236 is_true
238 Returns whether the (overloaded) boolean status of the value is true.
239 is_false
241 Returns whether the (overloaded) boolean status of the value is false.
242 create
244 FIXME
245 del_prop
247 FIXME
248 do_downto
250 FIXME
251 do_downto_step
253 FIXME
254 do_upto
256 FIXME
257 do_upto_step
259 FIXME
260 false
262 FIXME
263 gen_meth
265 FIXME
266 handle
268 FIXME
269 times_do
271 FIXME
272 true
274 FIXME
275 value
277 FIXME
278
280 pass_on(LIST)
281 Sets (replaces) the list of properties that are passed on. There is
282 only one such list for the whole mechanism. The whole property
283 interface is experimental, but this one in particular is likely to
284 change in the future. This function is exported automatically.
285 passed_on(STRING)
287 Tests whether a property is passed on and returns a boolean value. This
288 function is exported automatically.
289 get_pass_on
291 Returns a list of names of properties that are passed on. This function
292 is exported automatically.
293
295 See perlmodinstall for information and options on installing Perl
296 modules.
297
299 No bugs have been reported.
300 Please report any bugs or feature requests through the web interface at
302 <http://rt.cpan.org/Public/Dist/Display.html?Name=Scalar-Properties>.
303
305 The latest version of this module is available from the Comprehensive
306 Perl Archive Network (CPAN). Visit <http://www.perl.com/CPAN/> to find
307 a CPAN site near you, or see
308 <http://search.cpan.org/dist/Scalar-Properties/>.
309 The development version lives at
311 <http://github.com/hanekomu/Scalar-Properties/>. Instead of sending
312 patches, please fork this project using the standard git and github
313 infrastructure.
314
316 Marcel Gruenauer <marcel@cpan.org>
317
319 This software is copyright (c) 2001 by Marcel Gruenauer.
320 This is free software; you can redistribute it and/or modify it under
322 the same terms as the Perl 5 programming language system itself.
323perl v5.32.1 2021-01-27 Scalar::Properties(3)