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.\"
.IX Title "Sub::Util 3"
.TH Sub::Util 3 "2017-09-08" "perl v5.26.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
Sub::Util \- A selection of utility subroutines for subs and CODE references
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    use Sub::Util qw( prototype set_prototype subname set_subname );
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\f(CW\*(C`Sub::Util\*(C'\fR contains a selection of utility subroutines that are useful for
operating on subs and \s-1CODE\s0 references.
.PP
The rationale for inclusion in this module is that the function performs some
work for which an \s-1XS\s0 implementation is essential because it cannot be
implemented in Pure Perl, and which is sufficiently-widely used across \s-1CPAN\s0
that its popularity warrants inclusion in a core module, which this is.
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.SS "prototype"
.IX Subsection "prototype"
.Vb 1
\&    my $proto = prototype( $code )
.Ve
.PP
\&\fISince version 1.40.\fR
.PP
Returns the prototype of the given \f(CW$code\fR reference, if it has one, as a
string. This is the same as the \f(CW\*(C`CORE::prototype\*(C'\fR operator; it is included
here simply for symmetry and completeness with the other functions.
.SS "set_prototype"
.IX Subsection "set_prototype"
.Vb 1
\&    my $code = set_prototype $prototype, $code;
.Ve
.PP
\&\fISince version 1.40.\fR
.PP
Sets the prototype of the function given by the \f(CW$code\fR reference, or deletes
it if \f(CW$prototype\fR is \f(CW\*(C`undef\*(C'\fR. Returns the \f(CW$code\fR reference itself.
.PP
\&\fICaution\fR: This function takes arguments in a different order to the previous
copy of the code from \f(CW\*(C`Scalar::Util\*(C'\fR. This is to match the order of
\&\f(CW\*(C`set_subname\*(C'\fR, and other potential additions in this file. This order has
been chosen as it allows a neat and simple chaining of other
\&\f(CW\*(C`Sub::Util::set_*\*(C'\fR functions as might become available, such as:
.PP
.Vb 5
\& my $code =
\&    set_subname   name_here =>
\&    set_prototype \*(Aq&@\*(Aq      =>
\&    set_attribute \*(Aq:lvalue\*(Aq =>
\&       sub { ...... };
.Ve
.SS "subname"
.IX Subsection "subname"
.Vb 1
\&    my $name = subname( $code )
.Ve
.PP
\&\fISince version 1.40.\fR
.PP
Returns the name of the given \f(CW$code\fR reference, if it has one. Normal named
subs will give a fully-qualified name consisting of the package and the
localname separated by \f(CW\*(C`::\*(C'\fR. Anonymous code references will give \f(CW\*(C`_\|_ANON_\|_\*(C'\fR
as the localname. If a name has been set using \*(L"set_subname\*(R", this name will
be returned instead.
.PP
This function was inspired by \f(CW\*(C`sub_fullname\*(C'\fR from Sub::Identify. The
remaining functions that \f(CW\*(C`Sub::Identify\*(C'\fR implements can easily be emulated
using regexp operations, such as
.PP
.Vb 3
\& sub get_code_info { return (subname $_[0]) =~ m/^(.+)::(.+?)$/ }
\& sub sub_name      { return (get_code_info $_[0])[0] }
\& sub stash_name    { return (get_code_info $_[0])[1] }
.Ve
.PP
\&\fIUsers of Sub::Name beware\fR: This function is \fBnot\fR the same as
\&\f(CW\*(C`Sub::Name::subname\*(C'\fR; it returns the existing name of the sub rather than
changing it. To set or change a name, see instead \*(L"set_subname\*(R".
.SS "set_subname"
.IX Subsection "set_subname"
.Vb 1
\&    my $code = set_subname $name, $code;
.Ve
.PP
\&\fISince version 1.40.\fR
.PP
Sets the name of the function given by the \f(CW$code\fR reference. Returns the
\&\f(CW$code\fR reference itself. If the \f(CW$name\fR is unqualified, the package of the
caller is used to qualify it.
.PP
This is useful for applying names to anonymous \s-1CODE\s0 references so that stack
traces and similar situations, to give a useful name rather than having the
default of \f(CW\*(C`_\|_ANON_\|_\*(C'\fR. Note that this name is only used for this situation;
the \f(CW\*(C`set_subname\*(C'\fR will not install it into the symbol table; you will have to
do that yourself if required.
.PP
However, since the name is not used by perl except as the return value of
\&\f(CW\*(C`caller\*(C'\fR, for stack traces or similar, there is no actual requirement that
the name be syntactically valid as a perl function name. This could be used to
attach extra information that could be useful in debugging stack traces.
.PP
This function was copied from \f(CW\*(C`Sub::Name::subname\*(C'\fR and renamed to the naming
convention of this module.
.SH "AUTHOR"
.IX Header "AUTHOR"
The general structure of this module was written by Paul Evans
<leonerd@leonerd.org.uk>.
.PP
The \s-1XS\s0 implementation of \*(L"set_subname\*(R" was copied from Sub::Name by
Matthijs van Duin <xmath@cpan.org>
