Ubuntu Manpage: Scalar::Properties - Run-time properties on scalar variables

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Provided by: libscalar-properties-perl_1.100860-1_all

NAME

       Scalar::Properties - Run-time properties on scalar variables

VERSION

       version 1.100860

SYNOPSIS

         use Scalar::Properties;
         my $val = 0->true;
           if ($val && $val == 0) {
           print "yup, its true alright...\n";
         }

         my @text = (
           'hello world'->greeting(1),
           'forget it',
           'hi there'->greeting(1),
         );
         print grep { $_->is_greeting } @text;

         my $l =  'hello world'->length;

DESCRIPTION

Scalar::Properties attempts to make Perl more object-oriented by taking an idea from Ruby: Everything you
manipulate is an object, and the results of those manipulations are objects themselves.

'hello world'->length
(-1234)->abs
"oh my god, it's full of properties"->index('g')

The first example asks a string to calculate its length. The second example asks a number to calculate
its absolute value. And the third example asks a string to find the index of the letter 'g'.

Using this module you can have run-time properties on initialized scalar variables and literal values.
The word 'properties' is used in the Perl 6 sense: out-of-band data, little sticky notes that are
attached to the value. While attributes (as in Perl 5's attribute pragma, and see the "Attribute::*"
family of modules) are handled at compile-time, properties are handled at run-time.

Internally properties are implemented by making their values into objects with overloaded operators. The
actual properties are then simply hash entries.

Most properties are simply notes you attach to the value, but some may have deeper meaning. For example,
the "true" and "false" properties plays a role in boolean context, as the first example of the Synopsis
shows.

Properties can also be propagated between values. For details, see the EXPORTS section below. Here is an
example why this might be desirable:

pass_on('approximate');
my $pi = 3->approximate(1);
my $circ = 2 * $rad * $pi;

# now $circ->approximate indicates that this value was derived
# from approximate values

Please don't use properties whose name start with an underscore; these are reserved for internal use.

You can set and query properties like this:

"$var->myprop(1)"
sets the property to a true value.

"$var->myprop(0)"
sets the property to a false value. Note that this doesn't delete the property (to do so, use the
"del_props" method described below).

"$var->is_myprop", "$var->has_myprop"
returns a true value if the property is set (i.e., defined and has a true value). The two alternate
interfaces are provided to make querying attributes sound more natural. For example:

$foo->is_approximate;
$bar->has_history;

Values thus made into objects also expose various utility methods. All of those methods (unless noted
otherwise) return the result as an overloaded value ready to take properties and method calls itself, and
don't modify the original value.

METHODS

   get_props
       Get a list of names of the value's properties.

   del_props(LIST)
       Deletes one or more properties from the value. This is different than setting the property value to zero.

   del_all_props
       Deletes all of the value's properties.

   plus(EXPR)
       Returns the value that is the sum of the value whose method has been called and the argument value. This
       method also overloads addition, so:

         $a = 7 + 2;
         $a = 7->plus(2);    # the same

   minus(EXPR)
       Returns the value that is the the value whose method has been called minus the argument value. This
       method also overloads subtraction.

   times(EXPR)
       Returns the value that is the the value whose method has been called times the argument value. This
       method also overloads multiplication.

   divide(EXPR)
       Returns the value that is the the value whose method has been called divided by the argument value. This
       method also overloads division.

   modulo(EXPR)
       Returns the value that is the the value whose method has been called modulo the argument value. This
       method also overloads the modulo operator.

   exp(EXPR)
       Returns the value that is the the value whose method has been called powered by the argument value. This
       method also overloads the exponentiation operator.

   abs
       Returns the absolute of the value.

   zero
       Returns a boolean value indicating whether the value is equal to 0.

   length
       Returns the result of the built-in "length" function applied to the value.

   size
       Same as "length()".

   reverse
       Returns the reverse string of the value.

   uc
       Returns the result of the built-in function "uc()" applied to the value.

   ucfirst
       Returns the result of the built-in function "ucfirst()" applied to the value.

   lc
       Returns the result of the built-in function "lc()" applied to the value.

   lcfirst
       Returns the result of the built-in function "lcfirst()" applied to the value.

   hex
       Returns the result of the built-in function "hex()" applied to the value.

   oct
       Returns the result of the built-in function "oct()" applied to the value.

   concat(EXPR)
       Returns the result of the argument expression appended to the value.

   append(EXPR)
       Same as "concat(EXPR)".

   swapcase
       Returns a version of the value with every character's case reversed, i.e. a lowercase character becomes
       uppercase and vice versa.

   split /PATTERN/, LIMIT
       Returns a list of overloaded values that is the result of splitting (according to the built-in "split"
       function) the value along the pattern, into a number of values up to the limit.

   numcmp(EXPR)
       Returns the (overloaded) value of the numerical three-way comparison.  This method also overloads the
       "<=>" operator.

   cmp(EXPR)
       Returns the (overloaded) value of the alphabetical three-way comparison.  This method also overloads the
       "cmp" operator.

   eq(EXPR)
       Return the (overloaded) boolean value of the "eq" string comparison. This method also overloads that
       operators.

   ne(EXPR)
       Return the (overloaded) boolean value of the "ne" string comparison. This method also overloads that
       operators.

   lt(EXPR)
       Return the (overloaded) boolean value of the "lt" string comparison. This method also overloads that
       operators.

   gt(EXPR)
       Return the (overloaded) boolean value of the "gt" string comparison. This method also overloads that
       operators.

   le(EXPR)
       Return the (overloaded) boolean value of the "le" string comparison. This method also overloads that
       operators.

   ge(EXPR)
       Return the (overloaded) boolean value of the "ge" string comparison. This method also overloads that
       operators.

   eqi
       Same as "eq()", but is case-insensitive.

   nei>
       Same as "ne()", but is case-insensitive.

   lti
       Same as "lt()", but is case-insensitive.

   gti
       Same as "gt()", but is case-insensitive.

   lei
       Same as "le()", but is case-insensitive.

   gei
       Same as "ge()", but is case-insensitive.

   is_true
       Returns whether the (overloaded) boolean status of the value is true.

   is_false
       Returns whether the (overloaded) boolean status of the value is false.

   create
       FIXME

   del_prop
       FIXME

   do_downto
       FIXME

   do_downto_step
       FIXME

   do_upto
       FIXME

   do_upto_step
       FIXME

   false
       FIXME

   gen_meth
       FIXME

   handle
       FIXME

   times_do
       FIXME

   true
       FIXME

   value
       FIXME

FUNCTIONS

   pass_on(LIST)
       Sets (replaces) the list of properties that are passed on. There is only one such list for the whole
       mechanism. The whole property interface is experimental, but this one in particular is likely to change
       in the future. This function is exported automatically.

   passed_on(STRING)
       Tests whether a property is passed on and returns a boolean value. This function is exported
       automatically.

   get_pass_on
       Returns a list of names of properties that are passed on. This function is exported automatically.

INSTALLATION

       See perlmodinstall for information and options on installing Perl modules.

BUGS AND LIMITATIONS

       No bugs have been reported.

       Please report any bugs or feature requests through the web interface at
       <http://rt.cpan.org/Public/Dist/Display.html?Name=Scalar-Properties>.

AVAILABILITY

       The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit
       <http://www.perl.com/CPAN/> to find a CPAN site near you, or see
       <http://search.cpan.org/dist/Scalar-Properties/>.

       The development version lives at <http://github.com/hanekomu/Scalar-Properties/>.  Instead of sending
       patches, please fork this project using the standard git and github infrastructure.

AUTHOR

         Marcel Gruenauer <marcel@cpan.org>

COPYRIGHT AND LICENSE

       This software is copyright (c) 2001 by Marcel Gruenauer.

       This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5
       programming language system itself.