From: D M German <dmg@uvic.ca>
To: emacs-orgmode@gnu.org
Subject: bug in expansion of variables in babel Perl
Date: Sun, 24 Feb 2013 01:16:05 -0800 [thread overview]
Message-ID: <87ppzq138q.fsf@mn.cs.uvic.ca> (raw)
Hi Everybody,
I found a bug in the Babel perl code. When a table is used as input, the
values of the table are not escaped. In fact, they are surrounded by
double quotes " instead of single ones '. This means that special
characters are interpreted: $<string>, and @<variable are considered
variables. See below.
For example:
----------------------------------------------------------------------
#+RESULTS: patito
| alias | uniname |
|------------------------------------------------------+------------------------|
| Jon <tixy@xyz.org> | jon
#+name: output(data=patito)
#+begin_src perl :results output
print "Begin\n";
print $$data[0][0], "\n";
print "End\n";
#+end_src
#+RESULTS: output
: Begin
: Jon <tixy.org>
: End
----------------------------------------------------------------------
I see two ways to solve this. The first is simply to replace the output
format of the variable from "%S" to "'%s'" (use quotes '). The other one
is to optionally escape the fields of the table (which is more
complicated, and would require replacing each). The third one is a
combination of both: replace them only if desired, via some header
configuration variable.
diff --git a/lisp/ob-perl.el b/lisp/ob-perl.el
index ccd3826..2f795aa 100644
--- a/lisp/ob-perl.el
+++ b/lisp/ob-perl.el
@@ -75,7 +75,7 @@ The elisp value, VAR, is converted to a string of perl source code
specifying a var of the same value."
(if (listp var)
(concat "[" (mapconcat #'org-babel-perl-var-to-perl var ", ") "]")
- (format "%S" var)))
+ (format "'%s'" var)))
Debugging perl is very cumbersome in org-mode. It would be nice to have
a feature to export the source to a file. This is because the variable
expansion needs to be done before the code can be used (hence simply cut
and paste does not work, nor shell-command-on-region)
I used the org-babel-perl-command variable to replace perl with a script
that simply wrote to a file.
It would be nice to be able to write the script created by org a file,
so this can be debugged (it would have the variable definitions). Maybe
this is already a feature and I don't know about it.
As we are into it, I found this declaration to be very useful.
----------------------------------------------------------------------
(setq org-babel-perl-wrapper-method
"
use strict;
sub org_columns
{
my ($table) = @_;
my $y = $$table[0];
return scalar(@$y);
}
sub org_rows
{
my ($table) = @_;
return scalar(@$table);
}
sub main {
%s
}
my @r = main;
open(o, \">%s\");
print o join(\"\\n\", @r), \"\\n\"")
----------------------------------------------------------------------
It does two things: it uses strict, so undeclared variables create
errors, and it also creates two functions: org_columns and org_rows
that, when used on the variable declared as input, return its number of
columns and rows:
my $rows = org_rows($data);
my $columns = org_columns($data);
the only problem with using strict is that variables would have to be
defined with "my" too: so that would require this patch:
diff --git a/lisp/ob-perl.el b/lisp/ob-perl.el
index ccd3826..82f8086 100644
--- a/lisp/ob-perl.el
+++ b/lisp/ob-perl.el
@@ -62,7 +62,7 @@ This function is called by `org-babel-execute-src-block'."
"Return list of perl statements assigning the block's variables."
(mapcar
(lambda (pair)
- (format "$%s=%s;"
+ (format "my $%s=%s;"
(car pair)
(org-babel-perl-var-to-perl (cdr pair))))
(mapcar #'cdr (org-babel-get-header params :var))))
Finally, if interested, i can write a couple of examples for Perl that
could help people who want to use it.
thanks again,
--
Daniel M. German "Great algorithms are
Francis Sullivan -> the poetry of computation"
http://turingmachine.org/
http://silvernegative.com/
dmg (at) uvic (dot) ca
replace (at) with @ and (dot) with .
next reply other threads:[~2013-02-24 9:16 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-24 9:16 D M German [this message]
2013-02-24 9:45 ` bug in expansion of variables in babel Perl dmg
2013-02-24 10:23 ` D M German
2013-02-24 13:08 ` Achim Gratz
2013-02-24 18:20 ` D M German
2013-02-24 12:17 ` Achim Gratz
2013-02-24 16:52 ` Eric Schulte
2013-02-24 17:15 ` Achim Gratz
2013-02-24 18:03 ` Achim Gratz
2013-02-25 9:44 ` D M German
2013-02-24 17:05 ` [PATCH] " Achim Gratz
2013-02-25 9:42 ` D M German
2013-02-25 12:48 ` Achim Gratz
2013-02-25 21:54 ` D M German
2013-02-26 11:13 ` Achim Gratz
2013-03-02 22:01 ` Achim Gratz
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