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<!-- 
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<html>
<head> <title>
Gri Frequently Asked Questions
</title>
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<body bgcolor="#FFFFFF">

<h1> Introduction</h1>

This is the FAQ ("frequently asked questions") document for the Gri
scientific graphing language, (c) 1991-2003 Dan Kelley,
to whom you are asked to <A
HREF="mailto:dankelley@users.sourceforge.net"> email</A> reports of Gri errors, or
suggestions for Gri improvements or new features.



<h1> The Questions</h1>

<h2> Q1 Features</h2>
<UL>
<LI>
<A NAME="Q1.1">Q1.1</A>
<A HREF="#A1.1">What is Gri?</A>
<LI>
<A NAME="Q1.2">Q1.2</A>
<A HREF="#A1.2">What does `Gri' stand for?  How is it pronounced?</A>
<LI>
<A NAME="Q1.3">Q1.3</A>
<A HREF="#A1.3">What does Gri cost?</A>
<LI>
<A NAME="Q1.4">Q1.4</A>
<A HREF="#A1.4">How long will it take to learn Gri?</A>
</UL>


<h2> Q2 Documentation </h2>
<UL>
<LI>
<A NAME="Q2.1">Q2.1</A>
<A HREF="#A2.1">Is there a quick-reference card for Gri?</A>
<LI>
<A NAME="Q2.2">Q2.2</A>
<A HREF="#A2.2">Where can I get documentation for Gri?</A>
<LI>
<A NAME="Q2.3">Q2.3</A>
<A HREF="#A2.3">Is there a cookbook of Gri program to use for guidance?</A>
<LI>
<A NAME="Q2.4">Q2.4</A>
<A HREF="#A2.4">Is there a newsgroup for Gri?</A>
<LI>
<A NAME="Q2.5">Q2.5</A>
<A HREF="#A2.5">Where can I get some sample Gri input files?</A>
</UL>


<h2> Q3 Can Gri do ... ?</h2>
<UL>
<LI>
<A NAME="Q3.1">Q3.1</A>
<A HREF="#A3.1"> Can Gri do barcharts?</A>
<LI>
<A NAME="Q3.2">Q3.2</A>
<A HREF="#A3.2"> Can Gri do histograms?</A>
<LI>
<A NAME="Q3.3">Q3.3</A>
<A HREF="#A3.3"> Can Gri do error bars?</A>
<LI>
<A NAME="Q3.4">Q3.4</A>
<A HREF="#A3.4"> Can Gri draw labels for Tukey box plots?</A>
<LI>
<A NAME="Q3.5">Q3.5</A>
<A HREF="#A3.5"> Can Gri read compressed data files?</A>
<LI>
<A NAME="Q3.6">Q3.6</A>
<A HREF="#A3.6"> Can Gri use scientific notation on axes?</A>
<LI>
<A NAME="Q3.7">Q3.7</A>
<A HREF="#A3.7"> Can Gri label x-axis with day of week?</A>
<LI>
<A NAME="Q3.8">Q3.8</A>
<A HREF="#A3.8"> Can Gri draw maps?</A>
<LI>
<A NAME="Q3.9">Q3.9</A>
<A HREF="#A3.9"> Can Gri draw residuals on regressions?</A>

</UL>


<h2> Q4 Gri and other programs</h2>
<UL>
<LI>
<A NAME="Q4.1">Q4.1</A>
<A HREF="#A4.1">Is Gri better than Fortran/C/... plotting subroutines?</A>
<LI>
<A NAME="Q4.2">Q4.2</A>
<A HREF="#A4.2">How can I include Gri plots in LaTeX/word/... files?</A>
<LI>
<A NAME="Q4.3">Q4.3</A>
<A HREF="#A4.3">How may I convert Gri output to GIF format?</A>
<LI>
<A NAME="Q4.4">Q4.4</A>
<A HREF="#A4.4">Is there an Emacs mode for Gri?</A>
<LI>
<A NAME="Q4.5">Q4.5</A>
<A HREF="#A4.5">Is there a Gri module for perl/python/R/octave/...?</A>
</UL>


<h2> Q5 Evolution of Gri</h2>
<UL>
<LI>
<A NAME="Q5.1">Q5.1</A>
<A HREF="#A5.1">Where can I get the latest version of Gri?</A>
<LI>
<A NAME="Q5.2">Q5.2</A>
<A HREF="#A5.2">How can I find out the most recent features of Gri?</A>
<LI>
<A NAME="Q5.3">Q5.3</A>
<A HREF="#A5.3">Should I keep my copy of Gri up-to-date?</A>
<LI>
<A NAME="Q5.4">Q5.4</A>
<A HREF="#A5.4">How can I protect myself against changes to Gri?</A>
</UL>

<h2> Q6 Gri on various computers</h2>
<UL>
<LI>
<A NAME="Q6.1">Q6.1</A>
<A HREF="#A6.1">What computers does Gri work on?</A>
<LI>
<A NAME="Q6.2">Q6.2</A>
<A HREF="#A6.2">What kind of compiler is required to compile gri?</A>
<LI>
<A NAME="Q6.3">Q6.3</A>
<A HREF="#A6.3">Why can't I link my compiled gri? (on HP computer)</a>
<LI>
<A NAME="Q6.4">Q6.4</A>
<A HREF="#A6.4">Is there a Macintosh version of Gri?</A>
<LI>
<A NAME="Q6.5">Q6.5</A>
<A HREF="#A6.5">Is there a DOS/Windows version of Gri?</A>
<LI>
<A NAME="Q6.6">Q6.6</A>
<A HREF="#A6.6">Is there a linux version of Gri?</A>
</UL>


<h2> Q7 Gri bugs</h2>
<UL>
<LI>
<A NAME="Q7.1">Q7.1</A>
<A HREF="#A7.1"> What are known bugs in Gri?</A>
<LI>
<A NAME="Q7.2">Q7.2</A>
<A HREF="#A7.2"> How can I report Gri bugs?</A>
</UL>


<h1> The Answers</h1>

<hr>

<h2> A1 Features </h2>

<A NAME="A1.1"></A>
<A HREF="#Q1.1"><h3>A1.1 What is Gri?</h3></A>

<p> Gri is a program for drawing scientific graphs.  It makes xy plots
(linegraphs and scattergraphs), contour plots, and image plots.
Unlike many scientific plotting packages, Gri provides precise control
over fonts, line widths, grayscales, colors, etc.  Since Gri was
written by a scientist, it does the kinds of plots scientists want.
It has few frills; e.g., it does not do 3D mesh plots, because the
author dislikes them.  Gri is command-driven, not mouse driven.

<p>
<A NAME="A1.2"></A>
<A HREF="#Q1.2"><h3>A1.2 What does `Gri' stand for?  How is it pronounced?</h3></A>

<p> Gri stands for `<tt>gr-interactive</tt>', and `<tt>gr</tt>' is the
name of a subroutine library that preceded Gri.  The `interactive'
adjective indicates that Gri can be used interactively -- that is, Gri
is an interpreted language whereas Gr is a compiled language.  `Gri'
rhymes with `tree'.


<p>
<A NAME="A1.3"></A>
<A HREF="#Q1.3"><h3>A1.3 What does Gri cost?</h3></a>

<p> Gri is free.  A commercial version, called <A
HREF="http://www.phys.ocean.dal.ca/~kelley/gre">Gre</A>
will be made available soon.  It
contains most of Gri as a subset, but also contains quite a lot of the
<tt>Perl</tt> language as well, making it a fully functional and
efficient programming language.


<p>
<A NAME="A1.4"></A>
<A HREF="#Q1.4"><h3>A1.4 How long will it take to learn Gri?</h3></a>

<p> Most users can get Gri working after spending half an hour with
manual (see <a href="#Q2.1">Q2.1</a>).  Familiarity with your
operating system (for example for viewing PostScript files) will speed
this somewhat.  After that, it's best to learn new features only as
you come to need them.  To begin with, you should skim the manual and
the cookbook (see <a href="#Q2.3">Q2.3</a>), looking just at the
illustrations.  This will take no more than an hour.

<p> The Gri manual is like most computer manuals: it would be a waste
of time to read it cover to cover before starting to use Gri.  But
you'll find the manual helpful as you branch out, modifying the
existing examples and inventing code of your own.

<p> Learning how to use a new command usually takes only a minute but
realizing that the command exists can take longer.  That's why many
users with sophisticated needs find it useful to spend an afternoon
leafing through the entire manual at some point.

<p> Most things in Gri can be done elegantly or crudely.  The elegant
approach may require a little investment in time at the beginning, but
this will pay off constantly as your needs grow.  For example, folks
who like computer programming often start using Gri "newcommands" (a
form of subroutines) within a few days.  Other folks might avoid
newcommands, instead putting their entire program in one long "main
routine".  What's right for you depends on how you think and the sort
of work you do.




<hr>
<h2> A2 Documentation </h2>

<A NAME="A2.1"></A>
<A HREF="#Q2.1"><h3>A2.1 Is there a quick-reference card for Gri?</h3></A>

<p> Yes, two quick-reference cards are stored on the 
Gri development site
<A HREF="http://gri.sourceforge.net">
<code>http://gri.sourceforge.net</code>,
</A>
and these are also installed when gri is installed.
<p> 
<A NAME="A2.2"></A>
<A HREF="#Q2.2"><h3>A2.2 Where can I get documentation for Gri?</h3></A>

<p> Full documentation is available in several forms on the Gri 
development site
Gri development site
<A HREF="http://gri.sourceforge.net">
<code>http://gri.sourceforge.net</code>,
</A>
Check out the FAQ file (which you are
reading now), reference cards (see previous answer), etc.

<P> The Gri manual is available on the WWW (world wide web) at the URL
<a href="http://gri.sourceforge.net/gridoc/html/index.html">
http://gri.sourceforge.net/gridoc/html/index.html
</A>.

<A NAME="A2.3"></A>
<A HREF="#Q2.3"><h3>A2.3 Is there a cookbook of Gri programs to use for guidance?</h3></A>

Yes, at the website
<A HREF="http://gri.sourceforge.net/gri-cookbook/index.html"> 
<code>
http://gri.sourceforge.net/gri-cookbook/index.html
</code>
</a>


<p>
<A NAME="A2.4"></A>
<A HREF="#Q2.4"><h3>A2.4 Is there a newsgroup for Gri?</h3></A>

<p> Gri has several discussion forums at the development site
<A HREF="http://gri.sourceforge.net">
<code>http://gri.sourceforge.net</code>,
</A> and users are highly encouraged to participate!


<p> 
<A NAME="A2.5"></A>
<A HREF="#Q2.5"><h3>A2.5 Where can I get some sample Gri input files?</h3></A>

Sample files are scattered throughout the Gri manual and cookbook; the
manual also contains a test-suite that you may find helpful in
learning the language syntax, especially for programming.



<hr>
<h2> A3 Can Gri do ... ?</h2>
<A NAME="A3.1"></A>
<A HREF="#Q3.1"><h3>A3.1 Can Gri do barcharts?</h3></A>

<P> Gri has no specific command for barcharts, but the operating
system can easily rearrange your data into a form that lets Gri draw
barcharts.  In the following example, the synonym <CODE>\width</CODE>
is set to the desired width of the bars and <CODE>\missing</CODE> is
set to an arbitrary missing value.  The rest of the code will make
sense to any Perl programmer.  If you don't know Perl, you should
learn it.

<pre>
    \width = "1"                    // width of bars, in x units
    \missing = "-99"                // missing value
    set missing value \missing
    set x axis 0 6 1
    set y axis 0 20 10 
    draw axes none                  // will get whited out by the chart anyway

    // Create dataset
    system cat &gt; barchart.dat &lt;&lt; "EOF"
    1 12
    2 14
    3 15
    4 13
    5 10
    EOF

    // Create barchart style dataset and plot it
    system perl &lt;&lt;"EOF"
    open (IN, "barchart.dat") || die "Cannot open barchart.dat";
    while(&lt;IN&gt;) {
	($x[$i], $y[$i]) = split(' ');
	$i++;
    }
    $n = $i;
    open (TMP, "&gt;tmp") || die "Cannot open tmp";
    for ($i = 0; $i &lt; $n; $i++) {
	print TMP $x[$i] - \width / 2, " ",      0, "\n";
	print TMP $x[$i] - \width / 2, " ", $y[$i], "\n";
	print TMP $x[$i] + \width / 2, " ", $y[$i], "\n";
	print TMP $x[$i] + \width / 2, " ",      0, "\n";
	print TMP \missing, " ", \missing, "\n";
    }
    EOF
    open tmp
    read columns x y
    set graylevel 0.95
    draw curve filled to 0 y
    set graylevel 0
    draw curve
    draw axes
    draw title "Demonstrate Gri barchart"

</pre>

<A NAME="A3.2"></A>
<A HREF="#Q3.2"><h3>A3.2 Can Gri do histograms?</h3></A>

<P> Gri has no specific command for histograms, but the operating
system can easily rearrange your data into a histogram format.

<P> Here is Gri code to do it:
<pre>
    open "histogram -l 0 -h 10 -i 0.5 &lt inputfile |"
    read columns x y // y is number of obs
    draw curve filled to 0 y
</pre>

<P> where <code>histogram</code> is a perlscript which creates a
histogram file named <code>inputfile</code>.  An example of histogram
is:

<pre>
    #!/opt/bin/perl
    # Calculate histogram of 1-column data
    $usage ="\
    NAME\
	 histogram -- create histogram file, given data file (1 column)\
    \
    SYNOPSIS\
	 histogram -l low -h high -i increment &lt input_file &gt output_file\
    \
    DESCRIPTION\
	 Scans the input values and finds the percentage of data in bins\
	 starting at value `low', ending at value `high', and incrementing by\
	 value `inc'.\
    \
    FILES\
	 Standard input:  column of numbers\
	 Standard output: columns: (bin_centre, per, cum_per, num, cum_num)\
	     where 'per'=percentage and 'num'=number.\
    ";
    require "getopts.pl";
    $opt_l = 0;
    $opt_h = 0;
    $opt_i = 0;
    &Getopts('l:h:i:');
    die "You must supply commandline arguments!\n$usage" if ($opt_l == $opt_h || $opt_i == 0);
    $n = ($opt_h - $opt_l) / $opt_i;
    print STDERR "Will have $n bins, running from $opt_l to $opt_h in steps of $opt_i\n";
    for ($i = 0; $i &lt= $n; $i++) {
	$bin[$i] = 0;
    }
    while(&lt&gt) {
	chop;
	($x) = split;
	$i = int(0.5 + ($x - $opt_l) / $opt_i);
	$i =  0 if ($i &lt 0);
	$i = $n if ($i &gt $n);
	$bin[$i]++;
    }
    for ($i = 0; $i &lt= $n; $i++) {
	$x = $opt_l + $opt_i * ($i - 0.5);
	print "$x $bin[$i]\n";
	$x = $opt_l + $opt_i * ($i + 0.5);
	print "$x $bin[$i]\n";
    }
</pre>


<p>
<A NAME="A3.3"></A>
<A HREF="#Q3.3"><h3>A3.3 Can Gri do error bars?</h3></A>

<P> Gri has no specific command for error bars.  It has no internal
representation of error bar data -- that is, you can't get them by a
<code>read columns</code> command.  However, you can get error bars
quite easily, simply by reading the data line by line, plotting each
one as individually.  Here's an example of error bars in y, where the
third column stores the error:

<pre>
    open a.dat
    while 1
	read .x. .y. .ey.
	if ..eof..
	    break
	end if
	draw symbol bullet at .x. .y.
	draw line from .x. {rpn .y. .ey. -} to .x. {rpn .y. .ey. +}
    end while
</pre>


<A NAME="A3.4"></A>
<A HREF="#Q3.4"><h3>A3.4 Can Gri draw labels for Tukey box plots?</h3></A>

<P> Yes.  Here is sample code, in which a label "My Label" is drawn to
the right of the median of a Tukey plot extending in the y direction:

<pre>
    read columns x y
    1 11
    2 22
    1.2 3
    3 5
    2 20
    3 10

    draw y box plot at 2
    draw label "My Label" at {rpn 2 xusertocm 0.4 +} \
	{rpn y median yusertocm "M" ascent 2 / -} \
	cm
</pre>


<p> 
<A NAME="A3.5"></A>
<A HREF="#Q3.5"><h3>A3.5 Can Gri read compressed data files?</h3></A>

<P> Yes, as of version 2.6 Gri can read compressed files, e.g.
<pre>
    open myfile.gz
    read columns x y
</pre>
will work.  You may also, of course, do
<pre>
    open "zcat myfile.gz |"
    read columns x y
</pre>
if you like.


<p>
<A NAME="A3.6"></A>
<A HREF="#Q3.6"><h3>A3.6  Can Gri use scientific notation on axes?</h3></A>

<P> You have to trick it.  Here's an example:
<pre>
    // NOTE: this requires manual setting of axes.
    read columns x y
    1 1.1e3
    2 1.0e3
    3 1.4e3
    4 2.3e3
    4 1.0e4

    y /= 1e3
    set y axis 1 5 1
    set y format "%g$\times10^3$"
    draw curve
</pre>


<p>
<A NAME="A3.7"></A>
<A HREF="#Q3.7"><h3>A3.7 Can Gri label x-axis with day of week?</h3></A>

<P> A future version of Gri will have much more powerful and general
ways of handling axes labelling.  In the meantime, you have to trick
Gri to get such special effects.  Here's an example:

<pre>
    set x axis 1 8 1
    set y axis 0 1 .1
    set font size 0
    draw x axis at top
    draw y axis at right
    draw x axis at bottom
    set font size 12
    draw y axis at left
    draw label "Mon" centered at 1.5 {rpn ..ymargin.. 0.7 - ycmtouser}
    draw label "Tue" centered at 2.5 {rpn ..ymargin.. 0.7 - ycmtouser}
    draw label "Wed" centered at 3.5 {rpn ..ymargin.. 0.7 - ycmtouser}
    draw label "Thu" centered at 4.5 {rpn ..ymargin.. 0.7 - ycmtouser}
    draw label "Fri" centered at 5.5 {rpn ..ymargin.. 0.7 - ycmtouser}
    draw label "Sat" centered at 6.5 {rpn ..ymargin.. 0.7 - ycmtouser}
    draw label "Sun" centered at 7.5 {rpn ..ymargin.. 0.7 - ycmtouser}
</pre>

Note that the offset of <code>0.7</code> centimeters looks OK to me,
with a 12 point font, but you may wish to experiment if you don't like
the placement.


<p>
<A NAME="A3.8"></A>
<A HREF="#Q3.8"><h3>A3.8 Can Gri draw maps?</h3></A>

<P> Gri can draw maps, but it lacks builtin support for map
projections.  (A previous version had projections, but they were not
working correctly and were removed.)  Gri does not have builtin
coastline files, either.  Many good coastline files are on the web;
see, for example, Rich Signell's site
<A HREF="http://crusty.er.usgs.gov/coast/getcoast.html">
http://crusty.er.usgs.gov/coast/getcoast.html </A> or the USGS mapping
site <A HREF="http://www.usgs.gov"> http://www.usgs.gov </A> or the
Global Self-consistent Hierarchical High-resolution Shoreline site <A
HREF="http://www.ngdc.noaa.gov/mgg/shorelines/gshhs.html">
http://www.ngdc.noaa.gov/mgg/shorelines/gshhs.html </A>

<p>
<A NAME="A3.9"></A>
<A HREF="#Q3.9"><h3>A3.9 Can Gri draw residuals on regressions?</h3></A>
<p>There is no builtin command for that, but it's easy enough to
code, as follows:</p>
<pre>
read columns x y
0.05 12.5  
0.25 19    
0.5  15    
0.75 15    
0.95 13

draw regression line
# Draw the residuals individually
.i. = 0
while {rpn .i. ..num_col_data.. >}
    .x. = {rpn x .i. @}
    .y. = {rpn y .i. @}
    .ypred. = {rpn .x. ..coeff1.. * ..coeff0.. +}
    draw line from .x. .y. to .x. .ypred.
    .i. += 1
end while
</pre>


<hr>
<h2> A4 Gri and other programs </h2>
<A NAME="A4.1"></A>
<A HREF="#Q4.1"><h3>A4.1 Is Gri better than Fortran/C/... plotting subroutines?</h3></A>

<P> Gri started out as a set of subroutines.  The set is called `gr';
the name `gri' means gr-interactive.  Although I wrote both `gr' and
`gri', I haven't used gr in years.  I am unaware of anybody else who
ever used `gr'.  Thus, in at least this case, the interpreted Gri
language is superior to subroutines.

<P> In some applications the graphics are hard-wired into the
computation so using Gri might not make sense.  An example is the SPEM
numerical model, which has builtin NCAR plotting calls.  But this
approach is inefficient in user-time and computer-time, because
changing the format of the output may require re-running a model.  The
best approach is to decouple preparation of data from presentation of
data.

<P> In highly interactive applications, such as many uses of matlab
and statistical programs such as S and S-plus, it may make sense to
use the builtin graphics routines because they are so tightly bound to
the processing.



<A NAME="A4.2"></A>
<A HREF="#Q4.2"><h3>A4.2 How can I include Gri plots in LaTeX/Word/... files?</h3></A>

<h4>Latex</h4>
<P> There are several schemes for including PostScript figures, such
as those created by Gri, into LaTeX files.  That's unfortunate, in the
sense that it can confuse folks who are not experts.  The example
below works great at the moment, but 5 years ago a typical user might
have another command instead of <tt>includegraphics</tt>, and 5 years
from now there may be something new.  Still, I've found that
decade-old LaTeX files still work for me, so you shouldn't worry about
the chagnes.

<p>The example below includes the file <tt>fig.ps</tt> as a figure.
To test this, you may run a Gri script named <tt>fig.gri</tt>
consisting of the single command <tt>draw axes</tt>, and then save the
following into a file named <tt>test.tex</tt>, and then run LaTeX on
it, which in unix would mean typing <tt>latex test</tt> at the prompt.

<pre>
    \documentclass{article}
    \usepackage[dvips]{graphicx}

    \begin{document}

    \begin{figure}
    \includegraphics{fig.ps}
    \caption{Isn't this a nice graph?}
    \end{figure}

    Nice graph, eh?

    \end{document}
</pre>
<p>
It is worth noting that LaTeX has handled graphics in various ways
over the years.  The above indicates the preferred scheme as of 2001
or so, but other older schemes still work.

<h4>MS Word</h4>

All you need to do is to convert the file to GIF or PNG (see the next
question), or to another file format that MS word handles.  It is a
bad idea to use a JPEG format, since that doesn't work well on
linegraphs.

<p>
<A NAME="A4.3"></A>
<A HREF="#Q4.3"><h3>A4.3 How may I convert Gri output to GIF format?</h3></A>

<p> Conversion of the Gri PostScript output to GIF is normally done
for inclusion in web-pages.  For a discussion of the merits of various
image formats, see <A
HREF="http://www.lanl.gov/projects/ia">Information Architecture</A>.
I have been told that GIF images suffer from both technical
limitations (no gamma value is stored in the file) and license
restrictions.  The PNG format was designed to overcome these
limitations, and is expected to replace GIF over time.

<p> It should also be noted that there is no generally acceptable way
to convert PostScript to gif, especially when the PostScript is vector
based.  One problem is that of resolution: if the output GIF is
low-resolution, then the text may be drawn roughly because of
rasterization.  In many convertors one may specify the size of the
output image, which permits control over this resolution problem,
giving the user the task of weighing file size against output quality.
Note also that the colour table frequently gets reordered in the
conversion, possibly leading to inaccurate results.  Simply stated,
PostScript is superior to GIF and other raster-based formats.  That's
why Gri chose PostScript for the output model.

<p> There are several ways to convert Gri PostScript into GIF or PNG images.

<ul>

<LI> METHOD 1.  Use the <code>convert</code> program, which is a part
of the <code>ImageMagick</code> set of software.  The
<code>convert</code> software is quite powerful, being able to convert
from almost any format into almost any other, e.g.
<pre>
$ convert gri-1.ps gri-1.png
</pre>
If the output is to be used for the web, the above is fine.  If it's to be
imported into a word processor such as MS-Word, then the pixel resolution
is insufficient because the default is 72 dpi.  Try this instead:
<pre>
$ convert -density 300x300 gri-1.ps gri-1.png
</pre>
The <code>ImageMagick</code> software is free, and available on the
world-wide-web at URL <a
href="http://www.wizards.dupont.com/cristy/ImageMagick.html">
<code>http://www.wizards.dupont.com/cristy/ImageMagick.html</code>
</a>

<p>
<LI> METHOD 2: The GNU program <code>gs</code> can also do this
conversion.  In newer versions, this conversion to GIF is builtin.
Here is a shellscript
<pre>
    #!/usr/bin/sh
    gri -y -p -b $1.gri
    gs -q -dNOPAUSE -sDEVICE=ppm -sOutputFile=$1.ppm $1.ps -c quit
    ppmtogif -interlace -transparent rgb:ff/ff/ff $1.ppm > $1.gif
    rm -f $1.ppm
</pre>

<p>
<LI> METHOD 3: In older versions of <code>gs</code>, you must run a
little program in the <code>gs</code> interpreter, by typing  
<pre>
    $ gs foo.ps
    GS> (pstoppm.ps)run
    GS> (foo) ppm1run
    GS> quit
</pre>

This creates a file called <code>foo.ppm</code>, in the so-called PPM
format.  Various programs exist for converting image types,
e.g. <code>convert</code>.

</ul>

<p> Availability of software: ImageMagick uses Aladdin Ghostscript,
another free program, to rasterize the PostScript file created by gri.
Ghostscript is available from <A
HREF="http://www.cs.wisc.edu/~ghost/index.html">
<code>http://www.cs.wisc.edu/~ghost/index.html</code> </A> and many
other sites (including any CTAN archive).  Older version of
ghostscript are available under the GNU GPL.  Speaking of GNU,
<code>gs</code> and other GNU software are freely available at many
locations on the web, e.g.  <a href="ftp://prep.ai.mit.edu/pub/gnu">
<code>ftp://prep.ai.mit.edu/pub/gnu</code> </a>.


<p> <i>Author's note</i>: this answer was compiled with advice from
Peter Galbraith, Toru Suzuki, and George White, to each of whom I am
very grateful for the help.  In fact, the answer is mostly a patchwork
of their suggestions, and all the helpful pointers to information on
the web are theirs, not mine.


<p> 
<A NAME="A4.4"></A>
<A HREF="#Q4.4"><h3>A4.4 Is there an Emacs mode for Gri?</h3></A>

<p> Yes.  Peter Galbraith has written a very powerful mode for Gri
commandfiles which is supplied with Gri and which is fully documented
in the manual.  The capabilities of the mode include the following.

<UL>

<LI> Indents loops, if statements, newcommands, etc.

<LI> Uses built-in knowledge of Gri commands to 'complete' your
commands. For example, typing 'drM-TAB' (where M-TAB is the completion
keystroke) causes the mode to write 'draw' in place of the
'dr'. Pressing M-TAB again gives a list of all Gri commands starting
with 'draw'.

<LI> Provides complete access to Gri help on commands, including the
full Gri 'info' manual if your machine has that installed.  There is
even an 'apropos' feature to let you search for commands you're not
sure even exist.  

<LI> Lets you run Gri from within the buffer.  If syntax or runtime
Gri errors are encountered, the cursor (usually) moves to the
offending line in the Gri editing buffer.

<LI>  Lets you run Ghostview without leaving Emacs.

</UL>


<p> 
<A NAME="A4.5"></A>
<A HREF="#Q4.5"><h3>A4.5 Is there a Gri module for perl/python/R/octave/...?</h3></A>

<p> No.  The task of creating such modules is so time-consuming that
the Gri author cannot undertake it without help.  (Note: Gri contains
about 40,000 lines of C++ code.)

<hr>
<h2> A5 Evolution of Gri </h2>
<A NAME="A5.1"></A>
<A HREF="#Q5.1"><h3>A5.1 Where can I get the latest version of Gri?</h3></A>

Gri is available at the
Gri development site
<A HREF="http://gri.sourceforge.net">
<code>http://gri.sourceforge.net</code>,
</A>


<p>
<A NAME="A5.2"></A>
<A HREF="#Q5.2"><h3>A5.2 How can I find out the most recent features of Gri?</h3></A>

<P> Just visit the 
<a href="http://gri.sourceforge.net">
gri website
</a>
and look around; it's pretty simple.


<A NAME="A5.3"></A>
<A HREF="#Q5.3"><h3>A5.3 Should I keep my copy of Gri up-to-date?</h3></A>


<P> The advantages of being up-do-date are:

<UL>
<LI>You get new features.

<LI> There is a better chance of getting your bugs repaired, since all
bug fixes are applied only to the current version.)  The disadvantages
of being up-to-date are:

<LI> You can get clobbered by new bugs.  (You should avoid this by
keeping your old versions of Gri.  That means archiving both
<code>gri</code>, the executable, and <code>gri.cmd</code>, the
startup file.)

<LI> You can get clobbered by changes in the syntax.  This is the
penalty you pay for using a program under active development.  To
protect yourself, use the <code>expecting version</code> command,
which will warn you of any incompatibilites between the version you
expect and the version that is presently installed.

</UL>

<P> Most people should not be more than 5-10 versions out of date.  To
keep in touch, subscribe to the gri maillist (...see <a
href="#Q2.3">Q2.3</A>).  Also, keep track of the file ChangeLog in the FTP
location.  As with most software, the supplier may be more
enthusiastic about new versions than the users are.  Other Gri users
may therefore provide the best advice on whether it is worth
upgrading.



<p>
<A NAME="A5.4"></A>
<A HREF="#Q5.4"><h3>A5.4 How can I protect myself against changes to Gri?</h3></A>


<P> The most important thing is to save old versions of Gri.  At
hard-disk street prices of about a cent per megabyte, an archive will
cost under a nickle.

<p> Archiving the source is just a matter of copying the files you've
downloaded to a location of your choosing.  Since the directory name
is of the form <code>gri-VERSION</code>, keeping track of old sources
is trivial.

<p> If you're using a prepackaged version of Gri (e.g. in RedHat or in
Debian linux), then you'll probably know how to update Gri already.
At any rate, you can skip some of the steps below, since <code> rpm
-ql gri</code> will list all the relevant files, saving you the part
of the steps below that involves locating files.

<p> Archiving the Gri binary and library file is quite easy, but
archiving the documentation is complicated since there are a
<emph>lot</emph> of documentation files, and they are scattered across
your filesystem.  For example, 'info' files go in the
<code>/usr/info</code> directory, while 'manpage' files go in the
<code>/usr/man/man*</code> directory, and the 'html' files go
someplace else).  This isn't specific to Gri; the filesystem is just
defined that way, for historical reasons.  Your first step is to
determine whether you wish to archive the documentation.  In most case
you won't want to.  The point is just that you have an old set of
scripts that you need to work; you won't be writing new scripts, and
if you wrote these ones, then you understand Gri well enough anyway.
Besides, Gri doesn't change that much from version to version, and the
changes mostly involve additions.

<p> If you <emph>do</emph> wish to archive the documentation and emacs
files, locate the files and copy them.  (If you do not, skip the
remainder of this paragraph.)  In Redhat linux, do <code>rpm -ql
gri</code> to locate the files.  In debian linux, do something
similar.  If 'locate' is working on your computer, do <code>locate
gri</code> and examine the list that you get.  If none of the above is
true, look in the second-last paragraph above for directories where
Gri documentation files are often found, and move them to wherever
seems appropriate.  You'll probably have to alter other things as
well, to tell the <code>info</code> and <code>man</code> programs
where to find the documentation.  If you use the Emacs editing mode,
move that appropriately and edit whatever dot-files and system
configuration files that Emacs uses to locate mode files.  (Note that
all emacs modes understand about using different versions; see the
<code>C-c C-r</code> or by calling the command <code>M-x
gri-version</code>.  If, as is likely, you're only archiving Gri for
old scripts that you don't need to edit, you may not need to worry
about changes to gri-mode and you may as well go ahead and install the
new gri-mode and forget about the old one.)

<p> If you <emph>only</emph> wish to archive Gri itself, things are
<emph>much</emph> easier!  You need to copy only two files, the
executable (often <code>/usr/bin/gri</code>) and a library file (often
<code>/usr/share/gri/gri.cmd</code>) to a directory of your choosing,
and then create a shell alias (or a shellscript), which uses these two
files you've copied.  Let me take it step by step.

<p>
First, type
<pre>
    gri -version
</pre>
and make note of the present version number.  For concreteness, let's
say it is version 2.6.0.  

<p> 
Next, decide where you wish to keep this gri version.  For
concreteness, let's say that you'd like to keep it in
a directory named <code>/usr/local/gri/2.6.0</code>.  Create that
directory if it doesn't exist already:
<pre>
    mkdir -p /usr/local/gri/2.6.0
</pre>

<p>
Next, type
<pre>
    gri -directory_default
</pre>
to find out where the <code>gri.cmd</code> file is located.  Let's say
it's in the common location <code>usr/share/gri</code>, for
concreteness; then you need to move this to your chosen directory:
<pre>
    mv /usr/share/gri/gri.cmd /usr/local/gri/2.6.0
</pre>

<p>
Now, we need to copy the executable.  If you don't know where it is, type
<pre>
    which gri
</pre>
to find out.  Then move it also, e.g. if Gri is located in the
<code>/usr/bin</code> directory, you'd type
<pre>
    mv /usr/bin/gri /usr/local/gri/2.6.0
</pre>

<p>
Now we just have to make an alias to run this particular copy of Gri,
with this particular library file.  In the Bash shell, just put the
following line in your <code>~/.aliases</code> file:
<pre>
    alias gri2.6.0='/usr/local/gri/2.6.0/gri -directory /usr/local/gri/2.6.0'
</pre>
and then you have a new command, <code>gri2.6.0</code> that runs this
particular copy of Gri.  Alternatively, you could create a shellscript
to run this Gri, e.g. a script named <code>gri2.6.0</code> that
contains the lines:
<pre>
    #!/usr/bin/sh
    # Run numbered version of gri
    /usr/local/gri/2.6.0/gri -directory /usr/local/gri/2.6.0 "$@"
</pre>



<hr>
<h2> <strong>A6</strong> Gri on various computers </h2>

<A NAME="A6.1"></A>
<A HREF="#Q6.1"><h3>A6.1 What computers does Gri work on?</h3></A>

<P> Gri has been ported to several Unix machines (e.g. Sun solaris and
sunOS; IBM RISC; HP RISC; SGI; DEC alpha; and x86 linux) and to x86
MS-DOS.  An old version is available for DEC vax VMS.


<P>
<A NAME="A6.2"></A>
<A HREF="#Q6.2"><h3>A6.2 What kind of compiler is required to compile gri?</h3></A>

<p> Gri requires a C++ compiler capable of handling the language
feature called "templates," and it also needs the so-called "standard
template library" (STL).  Templates have been a feature of C++ since
about 1994, and STL became part of the draft C++ library standard in
early 1996.  If your compiler vendor does not support templates or
STL, you should obtain a newer compiler.

<p> The free C++ compiler called <code>g++</code>, available from the
Free Software Foundation, is known to compile Gri on at least a
half-dozen problems.  The compiler version must be 2.7.2 or higher for
success.


<P>
<A NAME="A6.3"></A>
<A HREF="#Q6.3"><h3>A6.3 Why can't I link my compiled gri? (on HP computer)</h3></A>

<p> Unfortunately, I made a bad programming decision several versions
ago -- I decided to start using the STL (the standard template
library).  The STL is part of the draft ANSI C++ standard, so I
figured I'd be safe.  And my tests on solaris and linux platforms
indicated that STL worked as advertised, in g++ 2.7.x.  However, I
should have checked further.  It turns out that g++ on some platforms
(e.g. HP's unix and IBMRS's AIX unix) does not handle templates
properly.  The linker cannot locate templates defined in one file and
used in another.  This issue is discussed at some length in the g++
documentation, where three methods are presented for solving the
problem.  (In the info-format documentation, you can find the relevant
parts by searching for the string "where's the template?")  In Gri
I've used what method 3 as defined in the g++ manual.  Apparently this
fails on some platforms.  Although I'd welcome tests by users on the
other two g++ methods, and I'd be happy to switch if one of them
appeared to work more universally, I have to say that I'm not
optimistic: from what I read on the newsgroups, nobody is having much
success on this.  The GNU folks say that g++ version 2.8 will handle
templates much better, so I'm waiting for that.  Unfortunately it's
been, so far, a two-year wait.

<p> Almost certainly, commercial compilers handle templates better,
but I lack resources to purchase these for the various platforms.  I'd
be happy, though, to act as a broker for anyone who is able to compile
Gri on the problematic platforms, and who is willing to share their
results.


<p> 
<A NAME="A6.4"></A>
<A HREF="#Q6.4"><h3>A6.4 Is there a Macintosh version of Gri?</h3></A>

<P> There once was a clicky-pointy Macintosh version of gri, but I got
frustrated with modifying the code each time Apple upgraded the OS and
stopped maintaining the code.  After several years of living (happily)
without the Macintosh, I flushed the Mac code down the drain.

<P> However, with the advent of OS-X, Gri compiles without
modification.  It has also been packaged for this system; check out
the 
<a href="http://fink.sourceforge.net/pdb/package.php/gri">
FINK</a> site to learn more about this project.

<p>
<A NAME="A6.5"></A>
<A HREF="#Q6.5"><h3>A6.5 Is there a DOS/Windows version of Gri?</h3></A>

<P> Versions of Gri have been available for MSDOS/Windows platforms
for years, kindly provided by Gri users with MSDOS/Windows machines.
In summer 2001, the porting procedure was systematized within the
GnuWin32 project.  This project provides win32 ports of GNU tools.  It
has been keeping very up-to-date with Gri development, trailing the
Unix versions by only a week or so.

Please visit
<A HREF="http://gnuwin32.sourceforge.net">
<code>http://gnuwin32.sourceforge.net</code>
</A>
for more on the GnuWin32 project, and to download Gri (and other GNU
software) for your windows platform.

<p> If, for some reason, you'd like to compile your own MSDOS/Windows
version, check the Gri manual under the heading 
<A HREF="http://gri.sourceforge.net/gridoc/html/msdos-install.html#Msdos-install">
Compilation on x86 (PC-style) Computers</A>.

<p> As for viewing Gri output, I recommend obtaining a copy of the
Ghostview program (which is a general PostScript display program), in
the version called 
<A HREF="http://www.cs.wisc.edu/~ghost/index.html">
GSview</A>.

<p>
<A NAME="A6.6"></A>
<A HREF="#Q6.6"><h3>A6.6 Is there a linux version of Gri?</h3></A>

<p> For non-RedHat versions of linux, one compiles and installs Gri in
the usual way; see 
<a href="http://gri.sourceforge.net/gridoc/html/index.html">
the manual
</a> for more details.

<P> Users of RedHat linux have it much easier though!  A RPM (RedHat
Program Manager) version of Gri exists, so that installing it takes
just one line of typing, or one mouse-click in a GUI interface to RPM.

<p> The RPM (RedHat Package Manager) version exists at the
Gri development site
<A HREF="http://gri.sourceforge.net">
<code>http://gri.sourceforge.net</code>,
</a>
Once you've downloaded this, install Gri by typing
<pre>
    rpm -i gri-2.1.17-1.i386.rpm
</pre>

Later on, Gri may be uninstalled ('extracted') by typing
<pre>
    rpm -e gri
</pre>

<p>
Knowledgeable RedHat users will know that RPM can also give
information about Gri; for non-experts, here are a few examples:
<pre>
    rpm -qa       --  list all installed packages
    rpm -qi gri   --  summarize gri capabilities (if it's installed)
    rpm -ql gri   --  list all files related to gri
</pre>


<hr>
<h2> <strong>A7</strong> Gri bugs </h2>

<A NAME="A7.1"></A>
<A HREF="#Q7.1"><h3>A7.1 What are known bugs in Gri?</h3></A>

<p> Gri is used daily by many users, including the author, so that it
suffers few serious bugs.  Generally, more recent versions of Gri
suffer fewer bugs than earlier versions.  This improvement owes much
to the trial of daily usage by folks with differing working styles;
and all users can thank those who send in bug reports (see <A
HREF="#Q7.2">Q7.2</A>).

<p> One of the main problems with recent versions of Gri is that line
numbers of syntax errors are reported inaccurately, if the error
occured inside a new-command.

<p> A list of 
<A HREF="http://gri.sourceforge.net/gridoc/html/KnownBugs.html#KnownBugs">
Gri bugs
</A>
is maintained in the manual.

<p>
<A NAME="A7.2"></A>
<A HREF="#Q7.2"><h3>A7.2 How can I report Gri bugs?</h3></A>

<p> The first step is to make sure it is actually a bug.  You might
try, for example, posting a question to the Gri newsgroup (see <a
href="#Q2.3">Q2.3</A>), and getting advice from other users.  Please
be clear, so you don't waste others users' time.  If you think you've
found a bug, let the author know.  Here's the advice from the manual
(see especially item 4, for directions on emailing bug reports):

<P> Your bug reports help make Gri reliable and useful.  Reporting
bugs often results in quick changes to gri which will solve your
problem.  This is especially true if your version is reasonably
up-to-date, for then you can simply get the corrected version and
replace the version you were using.  Here is how to report bugs.

<p> The details of how to report bugs is in the <a
href="http://gri.sourceforge.net/gridoc/html/ReportingBugs.html#ReportingBugs">online
documents </a>, but the quick answer is to go to
the
<a href="http://sourceforge.net/bugs/?group_id=5511">
Sourceforge Gri/bug site</a> and use the slick GUI
interface there.

</body>

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