What about built-in functions?
################################# From: This is perl, v5.6.1 built for MSWin32-x86-multi-thread (with 1 registered patch, see perl -V for more detail) Copyright 1987-2001, Larry Wall Binary build 628 provided by ActiveState Tool Corp. http://www.ActiveS +tate.com Built 15:41:05 Jul 4 2001 Perl may be copied only under the terms of either the Artistic License + or the GNU General Public License, which may be found in the Perl 5 source ki +t. Complete documentation for Perl, including FAQ lists, should be found +on this system using `man perl' or `perldoc perl'. If you have access to + the Internet, point your browser at http://www.perl.com/, the Perl Home Pa +ge. ################################# the documentation NAME attributes - get/set subroutine or variable attributes SYNOPSIS sub foo : method ; my ($x,@y,%z) : Bent ; my $s = sub : method { ... }; use attributes (); # optional, to get subroutine declarations my @attrlist = attributes::get(\&foo); use attributes 'get'; # import the attributes::get subroutine my @attrlist = get \&foo; DESCRIPTION Subroutine declarations and definitions may optionally have attrib +ute lists associated with them. (Variable "my" declarations also may, +but see the warning below.) Perl handles these declarations by passing + some information about the call site and the thing being declared along + with the attribute list to this module. In particular, the first exampl +e above is equivalent to the following: use attributes __PACKAGE__, \&foo, 'method'; The second example in the synopsis does something equivalent to th +is: use attributes __PACKAGE__, \$x, 'Bent'; use attributes __PACKAGE__, \@y, 'Bent'; use attributes __PACKAGE__, \%z, 'Bent'; Yes, that's three invocations. WARNING: attribute declarations for variables are an *experimental +* feature. The semantics of such declarations could change or be rem +oved in future versions. They are present for purposes of experimentati +on with what the semantics ought to be. Do not rely on the current implementation of this feature. There are only a few attributes currently handled by Perl itself ( +or directly by this module, depending on how you look at it.) However +, package-specific attributes are allowed by an extension mechanism. + (See the section on "Package-specific Attribute Handling" below.) The setting of attributes happens at compile time. An attempt to s +et an unrecognized attribute is a fatal error. (The error is trappable, +but it still stops the compilation within that "eval".) Setting an attrib +ute with a name that's all lowercase letters that's not a built-in att +ribute (such as "foo") will result in a warning with -w or "use warnings 'reserved'". Built-in Attributes The following are the built-in attributes for subroutines: locked Setting this attribute is only meaningful when the subroutine +or method is to be called by multiple threads. When set on a meth +od subroutine (i.e., one marked with the method attribute below), + Perl ensures that any invocation of it implicitly locks its first argument before execution. When set on a non-method subroutine +, Perl ensures that a lock is taken on the subroutine itself before execution. The semantics of the lock are exactly those of one explicitly taken with the "lock" operator immediately after th +e subroutine is entered. method Indicates that the referenced subroutine is a method. This has + a meaning when taken together with the locked attribute, as desc +ribed there. It also means that a subroutine so marked will not trig +ger the "Ambiguous call resolved as CORE::%s" warning. lvalue Indicates that the referenced subroutine is a valid lvalue and + can be assigned to. The subroutine must return a modifiable value +such as a scalar variable, as described in the perlsub manpage. There are no built-in attributes for anything other than subroutin +es. Available Subroutines The following subroutines are available for general use once this +module has been loaded: get This routine expects a single parameter--a reference to a subr +outine or variable. It returns a list of attributes, which may be emp +ty. If passed invalid arguments, it uses die() (via Carp::croak) to r +aise a fatal exception. If it can find an appropriate package name fo +r a class method lookup, it will include the results from a "FETCH_*type*_ATTRIBUTES" call in its return list, as describe +d in the section on "Package-specific Attribute Handling" below. Otherwise, only built-in attributes will be returned. reftype This routine expects a single parameter--a reference to a subr +outine or variable. It returns the built-in type of the referenced variable, ignoring any package into which it might have been blessed. This can be useful for determining the *type* value w +hich forms part of the method names described in the section on "Package-specific Attribute Handling" below. Note that these routines are *not* exported by default. Package-specific Attribute Handling WARNING: the mechanisms described here are still experimental. Do +not rely on the current implementation. In particular, there is no pro +vision for applying package attributes to 'cloned' copies of subroutines +used as closures. (See the section on "Making References" in the perlre +f manpage for information on closures.) Package-specific attribute handling may change incompatibly in a future release. When an attribute list is present in a declaration, a check is mad +e to see whether an attribute 'modify' handler is present in the approp +riate package (or its @ISA inheritance tree). Similarly, when "attributes::get" is called on a valid reference, a check is made +for an appropriate attribute 'fetch' handler. See the section on "EXAMPLE +S" to see how the "appropriate package" determination works. The handler names are based on the underlying type of the variable + being declared or of the reference passed. Because these attributes are associated with subroutine or variable declarations, this delibera +tely ignores any possibility of being blessed into some package. Thus, +a subroutine declaration uses "CODE" as its *type*, and even a bless +ed hash reference uses "HASH" as its *type*. The class methods invoked for modifying and fetching are these: FETCH_*type*_ATTRIBUTES This method receives a single argument, which is a reference t +o the variable or subroutine for which package-defined attributes ar +e desired. The expected return value is a list of associated attributes. This list may be empty. MODIFY_*type*_ATTRIBUTES This method is called with two fixed arguments, followed by th +e list of attributes from the relevant declaration. The two fixed arg +uments are the relevant package name and a reference to the declared subroutine or variable. The expected return value as a list of attributes which were not recognized by this handler. Note tha +t this allows for a derived class to delegate a call to its base clas +s, and then only examine the attributes which the base class didn't a +lready handle for it. The call to this method is currently made *during* the process +ing of the declaration. In particular, this means that a subroutine reference will probably be for an undefined subroutine, even i +f this declaration is actually part of the definition. Calling "attributes::get()" from within the scope of a null packag +e declaration "package ;" for an unblessed variable reference will n +ot provide any starting package name for the 'fetch' method lookup. T +hus, this circumstance will not result in a method call for package-def +ined attributes. A named subroutine knows to which symbol table entry i +t belongs (or originally belonged), and it will use the correspondin +g package. An anonymous subroutine knows the package name into which + it was compiled (unless it was also compiled with a null package declaration), and so it will use that package name. Syntax of Attribute Lists An attribute list is a sequence of attribute specifications, separ +ated by whitespace or a colon (with optional whitespace). Each attribut +e specification is a simple name, optionally followed by a parenthes +ised parameter list. If such a parameter list is present, it is scanned + past as for the rules for the "q()" operator. (See the section on "Quot +e and Quote-like Operators" in the perlop manpage.) The parameter list i +s passed as it was found, however, and not as per "q()". Some examples of syntactically valid attribute lists: switch(10,foo(7,3)) : expensive Ugly('\(") :Bad _5x5 locked method Some examples of syntactically invalid attribute lists (with annotation): switch(10,foo() # ()-string not balanced Ugly('(') # ()-string not balanced 5x5 # "5x5" not a valid identifier Y2::north # "Y2::north" not a simple identif +ier foo + bar # "+" neither a colon nor whitespa +ce EXPORTS Default exports None. Available exports The routines "get" and "reftype" are exportable. Export tags defined The ":ALL" tag will get all of the above exports. EXAMPLES Here are some samples of syntactically valid declarations, with annotation as to how they resolve internally into "use attributes" invocations by perl. These examples are primarily useful to see ho +w the "appropriate package" is found for the possible method lookups for package-defined attributes. 1. Code: package Canine; package Dog; my Canine $spot : Watchful ; Effect: use attributes Canine => \$spot, "Watchful"; 2. Code: package Felis; my $cat : Nervous; Effect: use attributes Felis => \$cat, "Nervous"; 3. Code: package X; sub foo : locked ; Effect: use attributes X => \&foo, "locked"; 4. Code: package X; sub Y::x : locked { 1 } Effect: use attributes Y => \&Y::x, "locked"; 5. Code: package X; sub foo { 1 } package Y; BEGIN { *bar = \&X::foo; } package Z; sub Y::bar : locked ; Effect: use attributes X => \&X::foo, "locked"; This last example is purely for purposes of completeness. You shou +ld not be trying to mess with the attributes of something in a package th +at's not your own. SEE ALSO the section on "Private Variables via my()" in the perlsub manpage + and the section on "Subroutine Attributes" in the perlsub manpage for details on the basic declarations; the attrs manpage for the obsol +escent form of subroutine attribute specification which this module repla +ces; the use entry in the perlfunc manpage for details on the normal invocation mechanism.
___crazyinsomniac_______________________________________
Disclaimer: Don't blame. It came from inside the void
perl -e "$q=$_;map({chr unpack qq;H*;,$_}split(q;;,q*H*));print;$q/$q;"
In reply to (crazyinsomniac) Re: Where in the Perl docs is use attributes documented?
by crazyinsomniac
in thread Where in the Perl docs is use attributes documented?
by princepawn
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