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perldl - Simple shell for PDL |
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.
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 ...
-w warnings)
turned-on.
perl switch.
perl switch.
perl switch.
perldlA perldl session can be terminated with any of the commands
quit, exit or the shorthands x or q.
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 sigints this should throw you back at the perldl
command prompt:
perldl> $result = start_lengthy_computation() <Ctrl-C> Ctrl-C detected
perldl>
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]
]
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 help
instead of
help 'help'
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 distribution 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 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: (Note: if you don't like the defaults change them in ~/.perldlrc)
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.
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).
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.
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 particular,
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.
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.
The user's home directory
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.
perldl promptA 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'.
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 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!
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
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 command 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 normal 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::NiceSlicePDL::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 the PDL::NiceSlice manpage.
PDL::NiceSlice installs a filter in the
preprocessing pipeline (see above) to enable the enhanced slicing
syntax. You can use a few commands 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.
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perldl - Simple shell for PDL |