** Using WeBWorK **

Following up on a suggestion of Mike's, I've developed an extension to
PGbasicmacros.pl to enable the display of Latex pictures in dvipng mode
(which produces much crisper graphics than the GD library). The new
routine is EV4(), whose source I attach below. [I hope it doesn't get
munged by the discussion board editor.]

It is used in problems in the following way:

TEXT(EV4(<<'END_TEXT'));
begin{picture}
....
end{picture}
END_TEXT

If we are in dvipng mode, then EV4() evaluates all Perl variables in
the text block and then ships the resulting Latex text off to dvipng.
Otherwise EV4() calls EV3().

Happy New Year to all,
Zig Fiedorowicz

sub EV4{
if ($displayMode eq "HTML_dpng") {
my $string = join(" ",@_);
my ($evaluated_string,$PG_eval_errors,$PG_full_errors) =
PG_restricted_eval("</>/g;
$evaluated_string = "\n$string\nend_of_evaluation_string\n");>

$main::PAR % ERROR in $0:EV3, PGbasicmacros.pl: $main::PAR % There is an error occuring in the following 
code:$main::BR $string $main::BR % $main::BR % $errorLines[0]n % 
$errorLines[1]$main::BR % $main::BR % $main::BR 

$string = $envir{'imagegen'}->add($string);
$string;
} else {EV3(@_);}
}

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Here's a related question. Looking through PGbasicmacros.pl I noticed
the following lines in the function general_math_ev3():

} elsif ($displayMode eq "HTML_img") {
$out = math2img($in, $mode);

Grepping through all the WeBWorK scripts, I could find no other
references to either HTML_img or math2img(). What is this code
supposed to do?

Zig

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I've posted problems using the above-mentioned constructions on our
web site at

https://webwork.math.ohio-state.edu/examples/151demo.tar.gz
https://webwork.math.ohio-state.edu/examples/152demo.tar.gz

Mike, could you add them to the CVS problem repository?

Let me add one other comment about Latex constructions and dvipng,
which doesn't seem to be documented. Here's how to do tables
so as come out right both in hard copy and dvipng (typeset2):

if ($main::displayMode ne 'HTML_dpng') {
#not dvipng mode: eg. hard copy or latex2html(typeset)
BEGIN_TEXT
\centerline{
\begin{tabular}{l|l}
\(x\) &\(F(x)\) \\
\hline
0 &\{ans_rule()\}\\

..........
\end{tabular}
}
END_TEXT
} else {
#dvipng(typeset2) mode
BEGIN_TEXT
<center>
<table border=2>
<tr><th width="40">\(x\)</th><th>\(F(x)\)</th></tr>
<tr><td align="center">0</td><td>{ans_rule()}</td></tr>
.......
</table>
</center>
END_TEXT
}

Zig

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There will be a few more changes that need to be made. The goal is to have a common set of macro files that can be used either by those using the current CGI driven version of WeBWorK or the new, available RSN mod_perl version.

I'll try to post your examples before I head out to the AMS meeting and if not as soon as I get back. As evidenced by my late posting I'm running more behind than usual.

-- Mike

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