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<head> <title> Gri Frequently Asked Questions </title></head>

<body>

<h1> Introduction</h1>

This is the FAQ ("frequently asked questions") document for the Gri
scientific graphing language, (c) 1991-1999 Dan Kelley <A
HREF="http://www.phys.ocean.dal.ca/~kelley">
(<CODE>Dan.Kelley@Dal.Ca</CODE>)</A>, to whom you are asked to <A
HREF="mailto:Dan.Kelley@Dal.Ca"> 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>
</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 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>
</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="#Q6.1">What computers does Gri work on?</A>
<LI>
<A NAME="Q6.2">Q6.2</A>
<A HREF="#Q6.2">What kind of compiler is required to compile gri?</A>
<LI>
<A NAME="Q6.3">Q6.3</A>
<A HREF="#Q6.3">Why can't I link my compiled gri? (on HP computer)</a>
<LI>
<A NAME="Q6.4">Q6.4</A>
<A HREF="#Q6.4">Is there a Macintosh version of Gri?</A>
<LI>
<A NAME="Q6.5">Q6.5</A>
<A HREF="#Q6.5">Is there a DOS/Windows version of Gri?</A>
<LI>
<A NAME="Q6.6">Q6.6</A>
<A HREF="#Q6.6">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 `gr-interactive', and `gr' 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 `try'.


<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> (rhymes with
`tree') will be made available in 1999.  It
contains most of Gri as a subset, but also contains quite a lot of the
Perl 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 <A
HREF="ftp://ftp.phys.ocean.dal.ca/users/kelley/gri">FTP site</A>
<code>ftp://ftp.phys.ocean.dal.ca/users/kelley/gri</code> (the base
address is 129.173.3.50).  The PostScript file <code>refcard.ps</code>
is an overview of Gri syntax and usage, while
<code>cmdrefcard.ps</code> is a full list of Gri commands.  Each of
these files is also available in TeX format.


<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 FTP site
<A HREF="ftp://ftp.phys.ocean.dal.ca/users/kelley/gri">FTP site</A>
<code>ftp://ftp.phys.ocean.dal.ca/users/kelley/gri</code> (the base
address is 129.173.3.50).  Check out the FAQ file (which you are
reading now), <CODE>cmdrefcard.ps</CODE> (a PostScript reference card
listing all Gri commands), <CODE>refcard.ps</CODE> (a PostScript
reference card overviewing Gri), and a file called something like
<CODE>gri_manual_2.051.tar.gz</CODE> (which is a complete PostScript
manual including figures).  To save time and paper, you should look at
the FAQ and the two reference cards first.

<P> The Gri manual is available on the WWW (world wide web) at the URL
<a href="http://www.phys.ocean.dal.ca/~kelley/gri/gri1.html">
http://www.phys.ocean.dal.ca/~kelley/gri/gri1.html </A>.  A searchable
index is available there, which is very useful.

<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://www.phys.ocean.dal.ca/~kelley/gri/cookbook/cookbook.html"> 
<code>http://www.phys.ocean.dal.ca/~kelley/gri/cookbook/cookbook.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> No, but there is a mail-list type newsgroup.  The group is
maintained automatically by a program called <code>majordomo</code>.
Operations like getting on or off the list are done by mailing to <A
HREF="mailto:majordomo@phys.ocean.dal.ca"><CODE>majordomo@phys.ocean.dal.ca</CODE></A>;
to subscribe, send a message containing just the two words
<code>subscribe gri</code>, and to unsubscribe send the words
<code>unsubscribe gri</code>.  You can also send the message
<code>help</code> to find out other usefull majordomo commands.

<p> To see what messages have been posted to the group, send a message
to <a
HREF="mailto:majordomo@phys.ocean.dal.ca"><CODE>majordomo@phys.ocean.dal.ca</CODE></A>
containing the line <code>send gri gri.archive</code>.

<p> Mailing to the list -- that is, to other Gri users -- is
different.  Then you mail to <A
HREF="mailto:gri@phys.ocean.dal.ca"><CODE>gri@phys.ocean.dal.ca</CODE></A>.
There is not very much traffic on the list, but please use it
responsibly because everything you send will be mailed to dozens of
other folks who are just as busy as you are.  In particular please do
<em>not</em> mail any requests intended for majordomo to the Gri list.


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

<p> You can get them from the anonymous <A
HREF="ftp://ftp.phys.ocean.dal.ca/users/kelley/gri">FTP site</A>
<code>ftp://ftp.phys.ocean.dal.ca/users/kelley/gri</code> (the base
address is 129.173.3.50).  It is in the compressed tarfile with the
word 'example' contained in it.  The file is compressed with the
program "gzip," so you'll type
<pre>
	gunzip gri-examples-2.1.10.tar.gz
	tar xvf  gri-examples-2.1.10.tar
</pre>
(where 2.1.10 will be changed to the current version number), and the
tar program will create a directory called 'examples' which contains
the example .gri programs and datafiles.  The 'examples' directory
also contains subdirectories with names that reflect computer names
(e.g., SGI, SUN4).  To get run gri on all the examples, go into the
appropriate subdirectory and type 'make examples'.  For example:
<pre>
	cd examples/SUN4
	make examples
</pre>
creates files <code>examples/SUN4/example1.ps</code>,
<code>examples/SUN4/example2.ps</code>, etc.



<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> Gri has no specific way to read compressed data files, but it is
trivial to trick it to do so, by using the unix-style piped open
command, as in this example:

<pre>
open "zcat compressed_file.Z |"
// do any normal 'read' commands 
</pre>

Naturally, this works for files that have been compressed with the GNU
compressor also, so long as you have the uncompressing software
installed on your system.

<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>


<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 files?</h3></A>

<P> This is done outside LaTeX (or TeX), with the program that
converts from DVI format to PostScript format.  This conversion is
done differently on different computers; you'll have to enquire
locally.  With `dvips', you can use the `\special' command or the
`\espfbox' command.  The epsfbox command is smarter, since it figures
the plot dimensions from the PostScript file itself.  Unfortunately,
old versions of Gri do not insert the correct plot dimensions in the
PostScript file.  Here's an example, for a 15cm tall figure, of how to
insert a Gri PostScript file into a figure:

<pre>
\documentstyle{article}
\begin{document}

... Figure \ref{fig1} shows ...

\begin{figure}
\vspace*{15cm}			% MAKE ENOUGH SPACE
\special{psfile=fig1.ps}	% THIS INSERTS THE PLOT
\caption[Short caption, which appears in list of figures.]
{\label{fig1} Long caption, which appears with the figure.}
\end{figure}

\end{document}
</pre>

In other LaTeX and TeX dialects, of course (e.g. the lovely agu++
format), you'll do things differently; the above will give you enough
of a guide.


<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 before the year 2000.

<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 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.  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.  To convert this to GIF format, you may use the
<code>xv</code> image viewer program (which is licensed shareware, not
freeware), or use the <code>ppmtogif</code> program in the pbmplus
package, available on the web at <a
href="ftp://ftp.x.org/congrib/utilities/netpbm-1mar1994.p1.tar.gz">
<code>ftp://ftp.x.org/congrib/utilities/netpbm-1mar1994.p1.tar.gz</code>
</a>.


</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.  Available on anonymous FTP at the site <a
href="ftp://ftp.phys.ocean.dal.ca/users/rhogee"> <code>
ftp.phys.ocean.dal.ca</code> in <code>users/rhogee </code></A>.  See
the files <code>gri-mode.el</code> and <code>gri-mode.readme</code>.
The capabilities include: <UL>

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

<LI> Uses builtin 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>




<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>

To get Gri, you use anonymous FTP to the site <a
href="ftp://ftp.phys.ocean.dal.ca/users/kelley/gri"> site</A> <code>
ftp.phys.ocean.dal.ca </code> or <code>129.173.3.50</code>.  (Use
'anonymous' as the username and your normal username as the password.)
Next, go to the Gri directory:
<pre>
        cd users/kelley/gri
</pre>
and get the instruction files:
<pre>
        mget README.*
</pre>

<P> These files tell you what to do next.  If you are not familiar with
such things, you might want to exit from FTP and read the README
files.  Otherwise, just do a directory listing and pick up the item
you want.  For example, to get the Sun binary version, get the file
with the word ``Sun'' in it:
<pre>
        binary
        get gri-binary-SunOS5-2.1.10.tar.gz
</pre>
and then type
<pre>
        quit
</pre>
to get out of FTP, and 
<pre>
        zcat gri-binary-SunOS5-2.1.10.tar.gz | gar xvf -
</pre>
to decode the contents.


<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> Do anonymous ftp to phys.ocean.dal.ca (129.173.3.50) and cd to the
directory /users/kelley/gri.  Pick up the file ChangeLog.  For
more details, see the chapter called "History" in the <a
href="http://www.phys.ocean.dal.ca/~kelley/gri/gri1.html"> manual</A>.

<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> Every time you get a new copy of Gri, you should get a new online
manual, and you should get/print the command reference card from the
<A HREF="ftp://ftp.phys.ocean.dal.ca/users/kelley/gri">FTP site</A>
<code>ftp://ftp.phys.ocean.dal.ca/users/kelley/gri</code> (the base
address is 129.173.3.50).


<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> Do three things:

<UL>

<LI> Use the <code>expecting version .n.</code> command, where you
replace <code>.n.</code> by the version number you are familiar with.
Then if the Gri you are using is more recent, it will tell you of any
changes in syntax since the version you've named.

<LI> When you download a new version of Gri, look at the file called
'changelog' in the
<A HREF="ftp://ftp.phys.ocean.dal.ca/users/kelley/gri">FTP site</A>
<code>ftp://ftp.phys.ocean.dal.ca/users/kelley/gri</code> (the base
address is 129.173.3.50).
It tells you what changes have taken place.

<LI> Archive old versions.  Each version takes about a Megabyte, which
costs less than a cup of coffee.  Since the author <em>does not</em>
archive old versions, you would be a little crazy not to do it
yourself, if you use Gri much at all.

<p> Archiving the source is just a matter of copying the files you've
downloaded to a location of your choosing.

<p> Archiving the binary is easy, since the process of installing a
new version automatically archives the old version.  On my machine,
and on other machines in the default configuration, the Gri files are
contained in a directory named <CODE>/opt/gri</CODE>.  Within the
<code>/opt/gri</code> directory are directories named
<code>bin</code>, which stores (a link to) the executable
<code>gri</code> file, and <code>lib</code>, which stores (links to)
the library file <code>gri.cmd</code> and the startup message file
<code>startup.msg</code>.  These links point to files within other
directories within <code>/opt/gri</code>, directories whose names are
Gri version numbers.  For example, if a system contained version 2.051
as the main Gri and 2.044 as an archived version,
<code>/opt/gri</code> would contain directories named
<code>bin</code>, <code>lib</code>, <code>2.051</code>, and
<code>2.044</code>.

<p> Each time a new version of Gri is installed, the remaining version
is left on disk, with the links in <code>/opt/gri/bin</code> and
<code>/opt/gri/lib</code> being severed and then reconnected to the
newer versions.  Thus, on my system I can run version 2.051 just by
typing

<pre>
    gri
</pre>

or I can run version 2.044 by explicitly naming it's source and the
directory for the library files, e.g. by typing.
<pre>
    /opt/gri/2.044/bin/gri -directory /opt/gri/2.044/lib
</pre>

On my system links are also created to put Gri in the system path,
e.g.
<pre>
    /opt/bin/bin/gri -> /opt/bin/bin/gri-2.048*
</pre>
and some users find it convenient to save typing with the old Gri
versions, by making additional links such as
<pre>
    /opt/bin/bin/gri-2.042 -> /opt/gri/2.042/bin/gri*
    /opt/bin/bin/gri-2.043 -> /opt/gri/2.043/bin/gri*
    /opt/bin/bin/gri-2.048 -> /opt/gri/2.048/bin/gri*
</pre>

<p> Also, the emacs mode understands about using different versions;
see the <code>C-c C-r</code> or by calling the command <code>M-x
gri-version</code>

</UL>


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

<A NAME="Q6.1"></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="Q6.2"></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="Q6.3"></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="Q6.4"></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 a version for Macintosh unix is <A
HREF="http://www.phys.ocean.dal.ca/~kelley/gri/Access.html#Mac-install">
available</A>.


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

<P> There is a version available for DOS, available at the normal Gri
FTP site, <A
HREF="ftp://ftp.phys.ocean.dal.ca/users/kelley/gri">
<code>ftp://ftp.phys.ocean.dal.ca/users/kelley/gri</code></A>, and copy
another at the anonymous FTP site 
<a href="ftp://shiho.tokyo-u-fish.ac.jp/pub/msdos/gri">
<code>
ftp://shiho.tokyo-u-fish.ac.jp/pub/msdos/gri
</code>
</a>
with filename of the form <code>gri2025b.zip</code> where 2025 refers
to the version name.  This binary version was prepared and very kindly
shared by Toru Suzuki <a href="mailto:toru@shiho.tokyo-u-fish.ac.jp">
<code>toru@shiho.tokyo-u-fish.ac.jp</code></a>.  Together with the distribution comes a file called <code>README</code>, which tells how to install and use Gri in an msdos context.


<p> Also, see the Gri manual under the heading <A
HREF="http://www.phys.ocean.dal.ca/~kelley/gri/Access.html#Msdos-install">
"Compilation on PC-style Computers" </A>

<p> As for viewing the 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="Q6.6"></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://www.phys.ocean.dal.ca/~kelley/gri">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 the RPM GUI-based
installer called `<tt>glint</tt>'.  requires just one line of typing
(or

<p> The RPM (RedHat Package Manager) version exists at FTP site <A
HREF="ftp://ftp.phys.ocean.dal.ca/users/kelley/gri"> <code>
ftp://ftp.phys.ocean.dal.ca/users/kelley/gri </code></a> in a file
with a name such as `<code>gri-2.1.17-1.i386.rpm</code>' (RedHat
readers will know immediately what all the numbers and dots stand
for!)  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 Gri bugs is maintained in the
<A HREF="http://www.phys.ocean.dal.ca/~kelley/gri/Bugs.html#Bugs">full manual</A>.


<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:

<UL>

<LI> 1. Determine the version number of your copy of Gri by running Gri as
<pre>
  gri -v
<pre>
and noting the number that is printed out.

<LI> 2. Prepare a command-file that illustrates your bug. Please pare
down the command-file to the *smallest* bit that causes the bug to
surface.

<LI> 3. It may be helpful to enclose the PostScript output file also,
if you need to tell me about aspects of the plot.  (This is because
the version of Gri I'm using might not give the badness on the page,
so I'd have no way to know what you were talking about!.)

<LI> 4. Email me 
(<A HREF="mailto:Dan.Kelley@Dal.CA">Dan.Kelley@Dal.Ca</A>) a description
of the bug, along with the enclosed command file and any necessary
data files.  Minimally, then, I'll need a README file that describes
the problem, and a gri commandfile that exercises the bug.  On a unix
machine, here is how you can the whole package to me:

<pre>
  tar -cvhf - ... | compress -c | uuencode a.gz | mail Dan.Kelley@Dal.Ca
</pre>
where you replace ... by a list of the files you want to send.
</UL>

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