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.\" ========================================================================
.\"
.IX Title "Kavorka::Manual::Functions 3pm"
.TH Kavorka::Manual::Functions 3pm "2019-01-17" "perl v5.28.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.SH "NAME"
Kavorka::Manual::Functions \- fun keyword
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Kavorka provides the \f(CW\*(C`fun\*(C'\fR keyword for the purpose of defining
functions (as against methods, etc).
.PP
The anatomy of a function:
.IP "1." 4
The keyword introducing the function.
.IP "2." 4
The function name (optional).
.IP "3." 4
The signature (optional).
.IP "4." 4
Traits (optional).
.IP "5." 4
The prototype (optional).
.IP "6." 4
The attribute list (optional).
.IP "7." 4
The function body.
.PP
Example:
.PP
.Vb 2
\&   #  (1) (2)    (3)          (4)     (5)   (6)     (7)
\&      fun foobar ($foo, $bar) is cool :($$) :cached { return $foo + $bar }
\&   
\&   #          (1) (6)
\&      my $f = fun { return $_[0] + $_[1] };
.Ve
.SS "The Keyword"
.IX Subsection "The Keyword"
This requires very little explanation. If you're no fun, and don't like
the name \f(CW\*(C`fun\*(C'\fR, you can export it with a different name:
.PP
.Vb 1
\&   use Kavorka fun => { \-as => \*(Aqfunction\*(Aq };
.Ve
.SS "The Function Name"
.IX Subsection "The Function Name"
If present, it specifies the name of the function being defined. If no
name is present, the declaration is an expression that evaluates to a
reference to the function in question.
.PP
Functions are automatically forward-declared; a la
.PP
.Vb 1
\&   sub foobar ($$);
.Ve
.PP
but are installed into the symbol table at run-time. So this works:
.PP
.Vb 6
\&   if ($ENV{DEBUG}) {
\&      fun foobar { ... }
\&   }
\&   else {
\&      fun foobar { ... }
\&   }
.Ve
.PP
It is possible to install the function at compile time using the
\&\f(CW\*(C`begin\*(C'\fR trait:
.PP
.Vb 1
\&   fun foobar but begin { ... }
.Ve
.PP
It is possible to define lexical functions using a lexical variable
for a function name:
.PP
.Vb 3
\&   fun my $add ($x, $y) {
\&      $x + $y;
\&   }
\&   
\&   my $sum = $add\->(20, 22);
.Ve
.SS "The Signature"
.IX Subsection "The Signature"
See Kavorka::Manual::Signatures.
.SS "Traits"
.IX Subsection "Traits"
See Kavorka::Manual::ExtendingKavorka.
.SS "The Prototype"
.IX Subsection "The Prototype"
See Kavorka::Manual::PrototypeAndAttributes.
.SS "The Attributes"
.IX Subsection "The Attributes"
Attributes may alternatively be provided \fIbefore the signature\fR.
.PP
See Kavorka::Manual::PrototypeAndAttributes.
.SS "The Function Body"
.IX Subsection "The Function Body"
This is more or less what you'd expect from the function body you'd
write with sub, however the lexical variables for parameters
are pre-declared and pre-populated.
.ie n .SS """f"", ""func"", and ""function"""
.el .SS "\f(CWf\fP, \f(CWfunc\fP, and \f(CWfunction\fP"
.IX Subsection "f, func, and function"
These are all aliases for \f(CW\*(C`fun\*(C'\fR, though not exported by default.
.PP
.Vb 2
\&   use v5.14;
\&   use Kavorka qw( function f );
\&   
\&   function make_plusser (Num $x = 1)
\&   {
\&      return f(Num $y) { $x + $y };
\&   }
\&   
\&   my $plusser = make_plusser();
\&   say $plusser\->(41);   # says 42
.Ve
.SH "BUGS"
.IX Header "BUGS"
Please report any bugs to
<http://rt.cpan.org/Dist/Display.html?Queue=Kavorka>.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Kavorka::Manual,
Kavorka::Manual::Signatures,
Kavorka::Manual::PrototypeAndAttributes,
Kavorka::Manual::MultiSubs.
.SH "AUTHOR"
.IX Header "AUTHOR"
Toby Inkster <tobyink@cpan.org>.
.SH "COPYRIGHT AND LICENCE"
.IX Header "COPYRIGHT AND LICENCE"
This software is copyright (c) 2013\-2014, 2017 by Toby Inkster.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
.SH "DISCLAIMER OF WARRANTIES"
.IX Header "DISCLAIMER OF WARRANTIES"
\&\s-1THIS PACKAGE IS PROVIDED \*(L"AS IS\*(R" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.\s0