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.IX Title "Demos 3pm"
.TH Demos 3pm 2024-04-22 "perl v5.38.2" "User Contributed Perl Documentation"
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.\" way too many mistakes in technical documents.
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.nh
.SH NAME
PDL::Demos \- PDL demo infrastructure
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 10
\&  # in a demo, if text\-orientated
\&  package PDL::Demos::Blah;
\&  sub info { (\*(Aqblah\*(Aq, \*(AqLonger description of demo\*(Aq) }
\&  sub init { \*(Aquse PDL::Graphics::PGPLOT;\*(Aq }
\&  my @demo = (
\&    [comment => "Welcome to the Blah demo"],
\&    [act => <<\*(AqEOF\*(Aq],
\&  output "PDL can make n\-dimensional sequences:\en";
\&  output $x = sequence(2,3);
\&  EOF
\&  );
\&  sub demo { @demo }
\&  sub done { "# return things to previous state\en" }
\&
\&  # a GUI\-orientated one
\&  package PDL::Demos::GUIBlah;
\&  use GUIBlah; # so demo won\*(Aqt show up in list if GUIBlah not installed
\&  sub info { (\*(Aqblahgui\*(Aq, \*(AqGUIBlah demo\*(Aq) }
\&  sub demo {[actnw => q|
\&    # starting up the GUI demo app
\&    |._\|_PACKAGE_\|_.q|::run();
\&  |]}
\&  sub run { # this is just a convention, but a good one
\&    # ...
\&  }
\&
\&  # iterate a demo of your own module \- call it PDL::Demos::(something)
\&  make && perl \-Mblib \-S perldl # run "demo" and it will see your demo
\&
\&  # in a CLI or REPL
\&  use PDL::Demos;
\&  sub demo {
\&    if (!$_[0]) {
\&      require List::Util;
\&      my @kw = sort grep $_ ne \*(Aqpdl\*(Aq, PDL::Demos\->keywords;
\&      my $maxlen = List::Util::max(map length, @kw);
\&      print "Use:\en";
\&      printf "   demo %\-${maxlen}s # %s\en", @$_[0,1] for map [PDL::Demos\->info($_)], \*(Aqpdl\*(Aq, @kw;
\&      return;
\&    }
\&    no strict;
\&    PDL::Demos\->init($_[0]);
\&    $_\->[0]\->($_\->[1]) for PDL::Demos\->demo($_[0]);
\&    PDL::Demos\->done($_[0]);
\&  }
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Provides utilities to make demos for PDL modules.
.PP
PDL demos should be in the \f(CW\*(C`PDL::Demos::*\*(C'\fR namespace so that they can
be auto-discovered.
.PP
Please ensure that your demo module is included in a CPAN distribution
and add it to the appropriate metadata (e.g. \f(CW\*(C`Makefile.PL\*(C'\fR and
\&\f(CW\*(C`MANIFEST\*(C'\fR).
.SH METHODS
.IX Header "METHODS"
.SS list
.IX Subsection "list"
Class method; goes through \f(CW@INC\fR finding all modules starting with
\&\f(CW\*(C`PDL::Demos::\*(C'\fR (with up to two \f(CW\*(C`::\*(C'\fR\-separated words). Cached after
first run. Does not distinguish demo modules that did not load.
.SS keywords
.IX Subsection "keywords"
Returns the list of keywords (first element of \f(CW\*(C`info\*(C'\fR return-list)
of all found modules that loaded successfully and implement an \f(CW\*(C`info\*(C'\fR
method. Caches results.
.SS info
.IX Subsection "info"
Given a keyword, returns the result of calling \f(CW\*(C`info\*(C'\fR on the relevant
module plus the module name (three elements) or throws exception if
unknown keyword.
.SS init
.IX Subsection "init"
Given a keyword, \f(CW\*(C`eval\*(C'\fRs the result of calling \f(CW\*(C`init\*(C'\fR on the relevant
module if it has one, or throws exception if unknown keyword.
.SS demo
.IX Subsection "demo"
Given a keyword, returns the result of calling \f(CW\*(C`demo\*(C'\fR on the relevant
module or throws exception if unknown keyword.
.SS done
.IX Subsection "done"
Given a keyword, \f(CW\*(C`eval\*(C'\fRs the result of calling \f(CW\*(C`done\*(C'\fR on the relevant
module if it has one, or throws exception if unknown keyword.
.SH "DEMO MODULE METHODS"
.IX Header "DEMO MODULE METHODS"
Each demo module must provide these class methods:
.IP info 4
.IX Item "info"
Return a two-element list of strings: a single keyword (probably
lower-case), and a short description of the demo.  Both will be displayed
when a user enters \f(CW\*(C`demo\*(C'\fR without giving a name.
.IP demo 4
.IX Item "demo"
Returns a list of array-refs of two elements: a function
provided by this module, and an argument for it.
.IP init 4
.IX Item "init"
Return a string of Perl code which will be evaluated in the package
running the demo. Use this e.g. for \f(CW\*(C`use\*(C'\fR statements that import
functions needed in your demo.
.SH FUNCTIONS
.IX Header "FUNCTIONS"
These are all exported.
.SS comment
.IX Subsection "comment"
Prints its argument, prompts user to press enter before returning.
.SS output
.IX Subsection "output"
Prints its argument (best for use in \f(CW\*(C`actnw\*(C'\fR etc).
.SS actnw
.IX Subsection "actnw"
The argument must be a string containing valid Perl code.  The string
is printed with a separator, then evaluated as Perl code in the
package running the demo, with \f(CW\*(C`PDL\*(C'\fR loaded. Doesn't prompt, so use
this for e.g. GUI demos that return when the user tells them to.
.PP
Multiline code string should start with a newline.
.SS act
.IX Subsection "act"
As above, but prompts before returning.
.SH "ERROR HANDLING"
.IX Header "ERROR HANDLING"
Check the prerequisites (e.g. optional Perl modules) for your demo in
your demo module and not only in the code string you pass to the
\&\f(CW\*(C`init\*(C'\fR routine.  If the code in your demo module dies, then the demo
will not be offered in the demo overview.  Fatal errors in the init
routine will be printed and mess up the output layout.  Also, error
messages might be difficult to understand if users just want to run
the demo.
.PP
If you want to show the demo in the overview though it can't run in
the current situation, then make sure that your \f(CW\*(C`demo\*(C'\fR method informs
the user what is missing, and where they can obtain it.
.SH AUTHOR
.IX Header "AUTHOR"
Copyright (C) 1998 Tuomas J. Lukka.
Tweaks by Ed J for PDL 2.077, 2022.