PERLDL(1)             User Contributed Perl Documentation            PERLDL(1)


       perldl - Simple shell for PDL


               %> perldl
               perldl> $a=sequence(10) # or any other PDL command


       The program perldl is a simple shell (written in perl) for interactive
       use of PDL.  perl/PDL commands can simply be typed in - and edited if
       you have appropriate version of the ReadLines and ReadKeys modules
       installed. In that case perldl also supports a history mechanism where
       the last 50 commands are always stored in the file .perldl_hist in your
       home directory between sessions. The command "l [number]" shows you the
       last "number" commands you typed where "number" defaults to 20.


          % perldl
          ReadLines enabled
          perldl> $a = rfits "foo.fits"
          BITPIX =  -32  size = 88504 pixels
          Reading  354016 bytes
          BSCALE =  &&  BZERO =

          perldl> imag log($a+400)
          Displaying 299 x 296 image from 4.6939525604248 to 9.67116928100586 ...

       Command-line options

       -tk Load Tk when starting the shell (the perl Tk module, which is
           available from CPAN must be installed). This enables readline event
           loop processing.

       -f file
           Loads the file before processing any user input. Any errors during
           the execution of the file are fatal.

       -w  Runs with warning messages (i.e. the normal perl "-w" warnings)

       -M module
           Loads the module before processing any user input.  Compare corre-
           sponding "perl" switch.

       -m module
           Unloads the module before processing any user input.

       -I directory
           Adds directory to the include path. (i.e. the @INC array) Compare
           corresponding "perl" switch.

       -V  Prints a summary of PDL config. This information should be included
           with any PDL bug report. Compare corresponding "perl" switch.

       Terminating "perldl"

       A "perldl" session can be terminated with any of the commands "quit",
       "exit" or the shorthands "x" or "q".

       Terminating commands (Ctrl-C handling)

       Commands executed within "perldl" can be terminated prematurely using
       "Ctrl-C" (or whichever key sequence sends an INT signal to the process
       on your terminal). Provided your PDL code does not ignore "sigint"s
       this should throw you back at the "perldl" command prompt:

         perldl> $result = start_lengthy_computation()
        Ctrl-C detected


       Shortcuts and aliases

       ·   The shell aliases "p" to be a convenient short form of "print",

              perldl> p ones 5,3

               [1 1 1 1 1]
               [1 1 1 1 1]
               [1 1 1 1 1]

       ·   "q" and "x" are short-hand for "quit".

       ·   "l" lists the history buffer

             perldl> l # list last 20 commands

             perldl> l 40 # list last 40 commands

       ·   "?" is an alias for help

             perldl> ? wpic

       ·   "??" is an alias for apropos

             perldl> ?? PDL::Doc

       ·   help, apropos, usage and sig: all words after these commands are
           used verbatim and not evaluated by perl. So you can write, e.g.,

               help help

           instead of

               help ’help’

       The startup file ~/.perldlrc

       If the file ~/.perldlrc is found it is sourced at start-up to load
       default modules, set shell variables, etc. If it is NOT found the dis-
       tribution file PDL/default.perldlrc is read instead. This loads various
       modules considered useful by default, and which ensure compatibility
       with v1.11. If you don’t like this and want a more streamlined set of
       your own favourite modules simple create your own ~/.perldlrc

       To set even more local defaults the file  local.perldlrc (in the cur-
       rent directory) is sourced if found. This lets you load modules and
       define subroutines for the project in the current directory.

       The name is chosen specfically because it was found hidden files were
       NOT wanted in these circumstances.

       Shell variables

       Shell variables: (Note: if you don’t like the defaults change them in

       ·   $PERLDL::ESCAPE  - default value ’#’

           Any line starting with this character is treated as a shell escape.
           The default value is chosen because it escapes the code from the
           standard perl interpreter.

       ·   $PERLDL::PAGER - default value "more"

           External program to filter the output of commands.  Using "more"
           prints output one screenful at a time.  On Unix, setting page(1)
           and $PERLDL::PAGER to "tee -a outfile" will keep a record of the
           output generated by subsequent perldl commands (without paging).

       ·   $PERLDL::PROMPT - default value ’perldl> ’

           Enough said  But can also be set to a subroutine reference, e.g.
           $PERLDL::PROMPT = sub {join(’:’,(gmtime)[2,1,0]).’> ’} puts the
           current time into the prompt.

       ·   $PERLDL::MULTI - default value 1

           If this is set to a true value, then perldl will parse multi-line
           perl blocks: your input will not be executed until you finish a
           line with no outstanding group operators (such as quotes, blocks,
           parenthesis, or brackets) still active.  Continuation lines have a
           different prompt that shows you what delimiters are still active.

           Note that this is not (yet!) a complete perl parser.  In particu-
           lar, Text::Balanced appears to be able to ignore quoting operatores
           like "q/ ... /" within a line, but not to be able to extend them
           across lines.  Likewise, there is no support for the ’<<’ operator.

           Multiline conventional strings and {}, [], and () groupings are
           well supported.

       ·   $PERLDL::NO_EOF - default value 0

           Protects against accidental use of "^D" from the terminal.  If this
           is set to a true value, then you can’t accidentally exit perldl by
           typing "^D".  If you set it to a value larger than 1 (and
           PERLDL::MULTI is set), then you can’t use "^D" to exit multiline
           commands either.  If you’re piping commands in from a file or pipe,
           this variable has no effect.

       ·   $HOME

           The user’s home directory

       ·   $PERLDL::TERM

           This is the Term::ReadLine object associated with the perldl shell.
           It can be used by routines called from perldl if your command is

       Executing scripts from the "perldl" prompt

       A useful idiom for developing perldl scripts or editing functions on-
       line is

             perldl> # emacs script &
                             -- add perldl code to script and save the file
             perldl> do ’script’

       -- substitute your favourite window-based editor for ’emacs’ (you may
       also need to change the ’&’ on non-Unix systems).

       Running "do ’script’" again updates any variables and function defini-
       tions from the current version of ’script’.

       Automatically execute your own hooks

       The variable @PERLDL::AUTO is a simple list of perl code strings and/or
       code reference. It is used to define code to be executed automatically
       every time the user enters a new line.

       A simple example would be to print the time of each command:

        perldl> push @PERLDL::AUTO,’print scalar(gmtime),"\n"’

        perldl> print zeroes(3,3)
        Sun May  3 04:49:05 1998

         [0 0 0]
         [0 0 0]
         [0 0 0]

        perldl> print "Boo"
        Sun May  3 04:49:18 1998

       Or to make sure any changes in the file ’local.perldlrc’ are always
       picked up :-

        perldl> push @PERLDL::AUTO,"do ’local.perldlrc’"

       This code can of course be put *in* ’local.perldlrc’, but be careful
       :-) [Hint: add "unless ($started++)" to above to ensure it only gets
       done once!]

       Another example application is as a hook for Autoloaders (e.g.
       PDL::AutoLoader) to add code too which allows them to automatically re-
       scan their files for changes. This is extremely convenient at the
       interactive command line. Since this hook is only in the shell it
       imposes no inefficiency on PDL scripts.

       Finally note this is a very powerful facility - which means it should
       be used with caution!

       Command preprocessing

       NOTE: This feature is used by default by PDL::NiceSlice.  See below for
       more about slicing at the "perldl" prompt

       In some cases, it is convenient to process commands before they are
       sent to perl for execution. For example, this is the case where the
       shell is being presented to people unfamiliar with perl but who wish to
       take advantage of commands added locally (eg by automatically quoting
       arguments to certain commands).

       *NOTE*: The preprocessing interface has changed from earlier versions!
       The old way using $PERLDL::PREPROCESS will still work but is strongly
       deprecated and might go away in the future.

       You can enable preprocessing by registering a filter with the "pre-
       proc_add" function. "preproc_add" takes one argument which is the fil-
       ter to be installed. A filter is a Perl code reference (usually set in
       a local configuration file) that will be called, with the current com-
       mand string as argument, just prior to the string being executed by the
       shell. The modified string should be returned. Note that you can make
       "perldl" completely unusable if you fail to return the modified string;
       quitting is then your only option.

       Filters can be removed from the preprocessing pipeline by calling "pre-
       proc_del" with the filter to be removed as argument.  To find out if a
       filter is currently installed in the preprocessing pipeline use "pre-

         perldl> preproc_add $myfilter unless preproc_registered $myfilter;

       Previous versions of "perldl" used the variable $PERLDL::PREPROCESS.
       This will still work but should be avoided. Please change your scripts
       to use the "preproc_add" etc functions.

       The following code would check for a call to function ’mysub’ and
       bracket arguments with qw.

        $filter = preproc_add sub {
          my $str = shift;
          $str =~ s/^\s+//;  # Strip leading space
          if ($str =~ /^mysub/) {
            my ($command, $arguments) = split(/\s+/,$str, 2);
            $str = "$command qw( $arguments )"
              if (defined $arguments && $arguments !~ /^qw/);
          # Return the input string, modified as required
          return $str;

       This would convert:

         perldl> mysub arg1 arg2


         perldl> mysub qw( arg1 arg2 )

       which Perl will understand as a list.  Obviously, a little more effort
       is required to check for cases where the caller has supplied a normal
       list (and so does not require automatic quoting) or variable interpola-
       tion is required.

       You can remove this preprocessor using the "preproc_del" function which
       takes one argument (the filter to be removed, it must be the same
       coderef that was returned from a previous "preproc_add" call):

         perldl> preproc_del $filter;

       An example of actual usage can be found in the "perldl" script. Look at
       the function "trans" to see how the niceslicing preprocessor is

       "perldl" and PDL::NiceSlice

       PDL::NiceSlice introduces a more convenient slicing syntax for piddles.
       In current versions of "perldl" niceslicing is enabled by default (if
       the required CPAN modules are installed on your machine).

       At startup "perldl" will let you know if niceslicing is enabled. The
       startup message will contain info to this end, something like this:

          perlDL shell v1.XX
           PDL comes with ABSOLUTELY NO WARRANTY. For details, see the file
           ’COPYING’ in the PDL distribution. This is free software and you
           are welcome to redistribute it under certain conditions, see
           the same file for details.
          ReadLines, NiceSlice  enabled
          Reading /home/csoelle/.perldlrc...
          Type ’demo’ for online demos
          Loaded PDL v2.XX

       When you get such a message that indicates "NiceSlice" is enabled you
       can use the enhanced slicing syntax:

         perldl> $a = sequence 10;
         perldl> p $a(3:8:2)

       For details consult PDL::NiceSlice.

       PDL::NiceSlice installs a filter in the preprocessing pipeline (see
       above) to enable the enhanced slicing syntax. You can use a few com-
       mands in the "perldl" shell to switch this preprocessing on or off and
       also explicitly check the substitutions that the NiceSlice filter

       You can switch the PDL::NiceSlice filter on and off by typing

         perldl> trans # switch niceslicing on


         perldl> notrans # switch niceslicing off

       respectively. The filter is on by default.

       To see how your commands are translated switch reporting on:

         perldl> report 1;
         perldl> p $a(3:8:2)
        processed p $a->nslice([3,8,2])
        [3 5 7]

       Similarly, switch reporting off as needed

         perldl> report 0;
         perldl>  p $a(3:8:2)
        [3 5 7]

       Reporting is off by default.

perl v5.8.6                       2005-05-12                         PERLDL(1)

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