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[catagits/Gitalist.git] / local-lib5 / man / man3 / Data::Dump.3pm

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.\" ========================================================================
.\"
.IX Title "Data::Dump 3"
.TH Data::Dump 3 "2009-07-26" "perl v5.8.7" "User Contributed Perl Documentation"
.SH "NAME"
Data::Dump \- Pretty printing of data structures
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& use Data::Dump qw(dump ddx);
.Ve
.PP
.Vb 2
\& $str = dump(@list);
\& @copy_of_list = eval $str;
.Ve
.PP
.Vb 2
\& # or use it for easy debug printout
\& ddx localtime;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module provide functions that takes a list of values as their
argument and produces a string as its result.  The string contains
Perl code that, when \f(CW\*(C`eval\*(C'\fRed, produces a deep copy of the original
arguments.
.PP
The main feature of the module is that it strives to produce output
that is easy to read.  Example:
.PP
.Vb 2
\&    @a = (1, [2, 3], {4 => 5});
\&    dump(@a);
.Ve
.PP
Produces:
.PP
.Vb 1
\&    (1, [2, 3], { 4 => 5 })
.Ve
.PP
If you dump just a little data, it is output on a single line. If
you dump data that is more complex or there is a lot of it, line breaks
are automatically added to keep it easy to read.
.PP
The following functions are provided (only the dd* functions are exported by default):
.IP "dump( ... )" 4
.IX Item "dump( ... )"
.PD 0
.IP "pp( ... )" 4
.IX Item "pp( ... )"
.PD
Returns a string containing a Perl expression.  If you pass this
string to Perl's built-in \fIeval()\fR function it should return a copy of
the arguments you passed to \fIdump()\fR.
.Sp
If you call the function with multiple arguments then the output will
be wrapped in parenthesis \*(L"( ..., ... )\*(R".  If you call the function with a
single argument the output will not have the wrapping.  If you call the function with
a single scalar (non\-reference) argument it will just return the
scalar quoted if needed, but never break it into multiple lines.  If you
pass multiple arguments or references to arrays of hashes then the
return value might contain line breaks to format it for easier
reading.  The returned string will never be \*(L"\en\*(R" terminated, even if
contains multiple lines.  This allows code like this to place the
semicolon in the expected place:
.Sp
.Vb 1
\&   print '$obj = ', dump($obj), ";\en";
.Ve
.Sp
If \fIdump()\fR is called in void context, then the dump is printed on
\&\s-1STDERR\s0 and then \*(L"\en\*(R" terminated.  You might find this useful for quick
debug printouts, but the dd*() functions might be better alternatives
for this.
.Sp
There is no difference between \fIdump()\fR and \fIpp()\fR, except that \fIdump()\fR
shares its name with a not-so-useful perl builtin.  Because of this
some might want to avoid using that name.
.ie n .IP "quote( $string )" 4
.el .IP "quote( \f(CW$string\fR )" 4
.IX Item "quote( $string )"
Returns a quoted version of the provided string.
.Sp
It differs from \f(CW\*(C`dump($string)\*(C'\fR in that it will quote even numbers and
not try to come up with clever expressions that might shorten the
output.
.IP "dd( ... )" 4
.IX Item "dd( ... )"
.PD 0
.IP "ddx( ... )" 4
.IX Item "ddx( ... )"
.PD
These functions will call \fIdump()\fR on their argument and print the
result to \s-1STDOUT\s0 (actually, it's the currently selected output handle, but
\&\s-1STDOUT\s0 is the default for that).
.Sp
The difference between them is only that \fIddx()\fR will prefix the lines
it prints with \*(L"# \*(R" and mark the first line with the file and line
number where it was called.  This is meant to be useful for debug
printouts of state within programs.
.SH "LIMITATIONS"
.IX Header "LIMITATIONS"
Code references will be displayed as simply 'sub { \*(L"???\*(R" }' when
dumped. Thus, \f(CW\*(C`eval\*(C'\fRing them will not reproduce the original routine.
.PP
If you forget to explicitly import the \f(CW\*(C`dump\*(C'\fR function, your code will
core dump. That's because you just called the builtin \f(CW\*(C`dump\*(C'\fR function
by accident, which intentionally dumps core.  Because of this you can
also import the same function as \f(CW\*(C`pp\*(C'\fR, mnemonic for \*(L"pretty\-print\*(R".
.SH "HISTORY"
.IX Header "HISTORY"
The \f(CW\*(C`Data::Dump\*(C'\fR module grew out of frustration with Sarathy's
in-most-cases-excellent \f(CW\*(C`Data::Dumper\*(C'\fR.  Basic ideas and some code
are shared with Sarathy's module.
.PP
The \f(CW\*(C`Data::Dump\*(C'\fR module provides a much simpler interface than
\&\f(CW\*(C`Data::Dumper\*(C'\fR.  No \s-1OO\s0 interface is available and there are no
configuration options to worry about (yet :\-).  The other benefit is
that the dump produced does not try to set any variables.  It only
returns what is needed to produce a copy of the arguments.  This means
that \f(CW\*(C`dump("foo")\*(C'\fR simply returns \f(CW"foo"\fR, and \f(CW\*(C`dump(1..5)\*(C'\fR simply
returns \f(CW\*(C`(1, 2, 3, 4, 5)\*(C'\fR.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Data::Dumper, Storable
.SH "AUTHORS"
.IX Header "AUTHORS"
The \f(CW\*(C`Data::Dump\*(C'\fR module is written by Gisle Aas <gisle@aas.no>, based
on \f(CW\*(C`Data::Dumper\*(C'\fR by Gurusamy Sarathy <gsar@umich.edu>.
.PP
.Vb 2
\& Copyright 1998\-2000,2003\-2004,2008 Gisle Aas.
\& Copyright 1996\-1998 Gurusamy Sarathy.
.Ve
.PP
This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.