name => 'optional',
default_arguments => 1,
check_argument_count => 0,
- attrs => ':method',
+ attributes => ':method',
shift => '$class',
},
);
$clean{shift} = delete $type{shift} || '';
_assert_valid_identifier $clean{shift}, 1 if $clean{shift};
- $clean{attrs} = delete $type{attrs} || '';
+ $clean{attrs} = join ' ', map delete $type{$_} || (), qw(attributes attrs);
_assert_valid_attributes $clean{attrs} if $clean{attrs};
$clean{default_arguments} =
use Function::Parameters;
+ # simple function
fun foo($bar, $baz) {
return $bar + $baz;
}
+ # function with prototype
fun mymap($fun, @args) :(&@) {
my @res;
for (@args) {
print "$_\n" for mymap { $_ * 2 } 1 .. 4;
+ # method with implicit $self
method set_name($name) {
$self->{name} = $name;
}
+ # function with default arguments
+ fun search($haystack, $needle = qr/^(?!)/, $offset = 0) {
+ ...
+ }
+
+ # method with default arguments
+ method skip($amount = 1) {
+ $self->{position} += $amount;
+ }
+
=cut
=pod
+ # use different keywords
use Function::Parameters {
proc => 'function',
meth => 'method',
The effect of C<fun foo($bar, $baz) {> is as if you'd written
C<sub foo { my ($bar, $baz) = @_; >, i.e. the parameter list is simply
-copied into C<my> and initialized from L<@_|perlvar/"@_">.
+copied into L<my|perlfunc/my> and initialized from L<@_|perlvar/"@_">.
In addition you can use C<method>, which understands the same syntax as C<fun>
but automatically creates a C<$self> variable for you. So by writing
=head2 Customizing the generated keywords
You can customize the names of the keywords injected into your scope. To do
-that you pass a hash reference in the import list:
+that you pass a reference to a hash mapping keywords to types in the import
+list:
+
+ use Function::Parameters {
+ KEYWORD1 => TYPE1,
+ KEYWORD2 => TYPE2,
+ ...
+ };
+
+Or more concretely:
use Function::Parameters { proc => 'function', meth => 'method' }; # -or-
use Function::Parameters { proc => 'function' }; # -or-
The first line creates two keywords, C<proc> and C<meth> (for defining
functions and methods, respectively). The last two lines only create one
-keyword. Generally the hash keys can be any identifiers you want while the
-values have to be either C<function>, C<method>, C<classmethod> or a hash
-reference (see below). The difference between C<function> and C<method> is that
-C<method>s automatically L<shift|perlfunc/shift> their first argument into
-C<$self> (C<classmethod>s are similar but shift into C<$class>).
+keyword. Generally the hash keys (keywords) can be any identifiers you want
+while the values (types) have to be either C<'function'>, C<'method'>,
+C<'classmethod'>, or a hash reference (see below). The main difference between
+C<'function'> and C<'method'> is that C<'method'>s automatically
+L<shift|perlfunc/shift> their first argument into C<$self> (C<'classmethod'>s
+are similar but shift into C<$class>).
The following shortcuts are available:
=pod
The following shortcuts are deprecated and may be removed from a future version
-of the module:
+of this module:
# DEPRECATED
use Function::Parameters 'foo';
That is, if you want to pass arguments to L<Function::Parameters>, use a
hashref, not a list of strings.
-You can customize things even more by passing a hashref instead of C<function>
-or C<method>. This hash can have the following keys:
+You can customize the properties of the generated keywords even more by passing
+a hashref instead of a string. This hash can have the following keys:
=over
this keyword will automatically L<shift|perlfunc/shift> its first argument into
a local variable whose name is specified here.
-=item C<attrs>
+=item C<attributes>, C<attrs>
Valid values: strings that are valid source code for attributes. Any value
specified here will be inserted as a subroutine attribute in the generated
code. Thus:
- use Function::Parameters { sub_l => { attrs => ':lvalue' } };
+ use Function::Parameters { sub_l => { attributes => ':lvalue' } };
sub_l foo() {
...
}
...
}
+It is recommended that you use C<attributes> in new code but C<attrs> is also
+accepted for now.
+
+=item C<default_arguments>
+
+Valid values: booleans. This property is on by default, so you have to pass
+C<< default_arguments => 0 >> to turn it off. If it is disabled, using C<=> in
+a parameter list causes a syntax error. Otherwise it lets you specify
+default arguments directly in the parameter list:
+
+ fun foo($x, $y = 42, $z = []) {
+ ...
+ }
+
+turns into
+
+ sub foo {
+ my ($x, $y, $z) = @_;
+ $y = 42 if @_ < 2;
+ $z = [] if @_ < 3;
+ ...
+ }
+
+except that none of the parameters are in scope in the expressions that specify
+default values. Thus:
+
+ my $var = "outer";
+
+ fun foo($var, $wat = $var) {
+ # $wat will default to "outer", not to what was passed
+ # as the first argument!
+ ...
+ }
+
+This may change in a future version of this module.
+
+=item C<check_argument_count>
+
+Valid values: booleans. This property is off by default. If it is enabled, the
+generated code will include checks to make sure the number of passed arguments
+is correct (and otherwise throw an exception via L<Carp::croak|Carp>):
+
+ fun foo($x, $y = 42, $z = []) {
+ ...
+ }
+
+turns into
+
+ sub foo {
+ Carp::croak "Not enough arguments for fun foo" if @_ < 1;
+ Carp::croak "Too many arguments for fun foo" if @_ > 3;
+ my ($x, $y, $z) = @_;
+ $y = 42 if @_ < 2;
+ $z = [] if @_ < 3;
+ ...
+ }
+
=back
-Plain C<'function'> is equivalent to C<< { name => 'optional' } >>, plain
-C<'method'> is equivalent to
-C<< { name => 'optional', shift => '$self', attrs => ':method' } >>, and plain
-C<'classmethod'> is equivalent to
-C<< { name => 'optional', shift => '$class', attrs => ':method' } >>.
+Plain C<'function'> is equivalent to:
+
+ {
+ name => 'optional',
+ default_arguments => 1,
+ check_argument_count => 0,
+ }
+
+(These are all default values so C<'function'> is also equivalent to C<{}>.)
+
+C<'method'> is equivalent to:
+
+ {
+ name => 'optional',
+ default_arguments => 1,
+ check_argument_count => 0,
+ attributes => ':method',
+ shift => '$self',
+ }
+
+C<'classmethod'> is equivalent to:
+
+ {
+ name => 'optional',
+ default_arguments => 1,
+ check_argument_count => 0,
+ attributes => ':method',
+ shift => '$class',
+ }
=head2 Syntax and generated code
C<$bar-E<gt>foo([1], $bar[0])>. Yes. You can add parens to change the
interpretation of this code, but C<foo($bar[1], $bar[0])> will only trigger
a I<foo() called too early to check prototype> warning. This module attempts
-to fix all of this by adding a subroutine declaration before the definition,
+to fix all of this by adding a subroutine declaration before the function body,
so the parser knows the name (and possibly prototype) while it processes the
body. Thus C<fun foo($x) :($) { $x }> really turns into
-C<sub foo ($); sub foo ($) { my ($x) = @_; $x }>.
+C<sub foo ($) { sub foo ($); my ($x) = @_; $x }>.
If you need L<subroutine attributes|perlsub/"Subroutine Attributes">, you can
put them after the parameter list with their usual syntax.
because normal attributes have to start with a letter while a prototype starts
with C<(>).
-As an example, the following declaration uses every feature available
-(subroutine name, parameter list, prototype, attributes, and implicit
-C<$self>):
+As an example, the following declaration uses every available feature
+(subroutine name, parameter list, default arguments, prototype, default
+attributes, attributes, argument count checks, and implicit C<$self>):
- method foo($x, $y, @z) :($;$@) :lvalue :Banana(2 + 2) {
+ method foo($x, $y, $z = sqrt 5) :($$$;$) :lvalue :Banana(2 + 2) {
...
}
And here's what it turns into:
- sub foo ($;$@); sub foo ($;$@) :lvalue :Banana(2 + 2) { my $self = shift; my ($x, $y, @z) = @_;
+ sub foo ($$$;$) :method :lvalue :Banana(2 + 2) {
+ sub foo ($$$;$);
+ Carp::croak "Not enough arguments for method foo" if @_ < 2;
+ Carp::croak "Too many arguments for method foo" if @_ > 4;
+ my $self = shift;
+ my ($x, $y, $z) = @_;
+ $z = sqrt 5 if @_ < 3;
...
}
And the generated code:
- my $coderef = sub (;$$) :lvalue :Gazebo((>:O)) { my ($p, $q) = @_;
+ my $coderef = sub (;$$) :lvalue :Gazebo((>:O)) {
+ # vvv only if check_argument_count is enabled vvv
+ Carp::croak "Not enough arguments for fun (anon)" if @_ < 2;
+ Carp::croak "Too many arguments for fun (anon)" if @_ > 2;
+ my ($p, $q) = @_;
...
};
use Function::Parameters ();
sub import {
Function::Parameters->import;
- # or Function::Parameters->import(@other_import_args);
+ # or Function::Parameters->import(@custom_import_args);
}
=head1 AUTHOR
projects / p5sagit/Function-Parameters.git / commitdiff