PERLDL(1) User Contributed Perl Documentation PERLDL(1)
NAME
perldl - Simple shell for PDL
SYNOPSIS
%> perldl
perldl> $a=sequence(10) # or any other PDL command
DESCRIPTION
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.
e.g.:
% 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) turned-on.
-M module
Loads the module before processing any user input. Compare corresponding "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>
Ctrl-C detected
perldl>
Shortcuts and aliases
o The shell aliases "p" to be a convenient short form of "print", e.g.
perldl> p ones 5,3
[
[1 1 1 1 1]
[1 1 1 1 1]
[1 1 1 1 1]
]
o "q" and "x" are short-hand for "quit".
o "l" lists the history buffer
perldl> l # list last 20 commands
perldl> l 40 # list last 40 commands
o "?" is an alias for help
perldl> ? wpic
o "??" is an alias for apropos
perldl> ?? PDL::Doc
o 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 compatibil-
ity 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 current 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 ~/.perldlrc)
o $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.
o $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).
o $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 cur-
rent time into the prompt.
o $HOME
The user's home directory
o $PERLDL::TERM
This is the Term::ReadLine object associated with the perldl shell. It can be used by routines called from perldl if your command is
interactive.
Executing scripts from the "perldl" prompt
A useful idiom for developing perldl scripts or editing functions on-line is
perldl> # emacs script &
-- add perldl code to script and save the file
perldl> do 'script'
-- substitute your favourite window-based editor for 'emacs' (you may also need to change the '&' on non-Unix systems).
Running "do 'script'" again updates any variables and function definitions from the current version of 'script'.
Automatically execute your own hooks
The variable @PERLDL::AUTO is a simple list of perl code strings and/or code reference. It is used to define code to be executed automati-
cally every time the user enters a new line.
A simple example would be to print the time of each command:
perldl> push @PERLDL::AUTO,'print scalar(gmtime),"\n"'
perldl> print zeroes(3,3)
Sun May 3 04:49:05 1998
[
[0 0 0]
[0 0 0]
[0 0 0]
]
perldl> print "Boo"
Sun May 3 04:49:18 1998
Boo
perldl>
Or to make sure any changes in the file 'local.perldlrc' are always picked up :-
perldl> push @PERLDL::AUTO,"do 'local.perldlrc'"
This code can of course be put *in* 'local.perldlrc', but be careful :-) [Hint: add "unless ($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 quot-
ing 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 "preproc_add" function. "preproc_add" takes one argument which is the filter
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 "preproc_del" with the filter to be removed as argument. To find out if
a filter is currently installed in the preprocessing pipeline use "preproc_registered":
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
to
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 nor-
mal list (and so does not require automatic quoting) or variable interpolation 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
enabled/disabled.
"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
makes.
You can switch the PDL::NiceSlice filter on and off by typing
perldl> trans # switch niceslicing on
and
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 v5.8.0 2003-01-29 PERLDL(1)