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Chris Marshall > PDL > PDL::AutoLoader


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PDL::AutoLoader - MatLab style AutoLoader for PDL


 use PDL::AutoLoader;
 $a = func1(...);   # Load file func1.pdl
 $b = func2(...);   # Load file func2.pdl

 $PDL::AutoLoader::Rescan = 1; # Enable re-scanning


This module implements a MatLab style AutoLoader for PDL. If an unknown function func() is called, PDL looks for a file called func.pdl. If it finds one, it compiles the file and calls the function func.

The list of directories to search in is given by the shell environment variable PDLLIB. This is a colon-separated list of directories. On MSWindows systems, is it a semicolon -separated list of directories.

For example, in csh:

  setenv PDLLIB "/home/joe/pdllib:/local/pdllib"

Note: This variable is unrelated to Perl's PERL5LIB.

If you add a leading '+' on a directory name, PDL will search the entire directory tree below that point. Internally, PDL stores the directory list in the variable @PDLLIB, which can be modified at run time.

For example, in csh:

  setenv PDLLIB "+/home/joe/PDL"

will search /home/joe/PDL and all its subdirectories for .pdl files.


The variable $PDL::AutoLoader::Rescan controls whether files are automatically re-scanned for changes at the perldl or pdl2 command line.

If $PDL::AutoLoader::Rescan == 1 and the file is changed then the new definition is reloaded auto-matically before executing the perldl or pdl2 command line. Which means in practice you can edit files, save changes and have perldl or pdl2 see the changes automatically.

The default is '0' - i.e. to have this feature disabled.

As this feature is only pertinent to the PDL shell it imposes no overhead on PDL scripts. Yes Bob you can have your cake and eat it too!

Note: files are only re-evaled if they are determined to have been changed according to their date/time stamp.

No doubt this interface could be improved upon some more. :-)

Sample file:

 sub foo { # file 'foo.pdl' - define the 'foo' function
   my $x=shift;
   return sqrt($x**2 + $x**3 + 2);
 1; # File returns true (i.e. loaded successfully)


Copyright(C) 1997 Karl Glazebrook (; several extensions by Craig DeForest ( All rights reserved. There is no warranty. You are allowed to redistribute this software / documentation under certain conditions. For details, see the file COPYING in the PDL distribution. If this file is separated from the PDL distribution, the copyright notice should be included in the file.


No doubt this interface could be improved upon some more. :-)

Will probably be quite slow if $PDL::AutoLoader::Rescan == 1 and thousands of functions have been autoloaded.

There could be a race condition in which the file changes while the internal autoloader code is being executed but it should be harmless.

Probably has not been tested enough!


For an alternative approach to managing a personal collaction of modules and functions, see local::lib.


Expand a compactified path into a dir list

You supply a pathlist and leading '+' and '~' characters get expanded into full directories. Normally you don't want to use this -- it's internal to the autoloader -- but some utilities, like the online documentation searcher, need to be able to use it.

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