simplegraph.fsp - Frink Server Pages Highlighter

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  <TITLE>Interval Graph</TITLE>
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<% // Read in arguments to be graphed, or set up interesting defaults.

    if (! func)
    {
       func = "x^2 + y^2 = 81 sin[x]^2"
       xmin = ymin = -10
       xmax = ymax = 10
       xsteps = 121
       ysteps = 39
       pscale = 1
    } else
    {
       xmin = eval[xmin]
       ymin = eval[ymin]
       xmax = eval[xmax]
       ymax = eval[ymax]
       xsteps = eval[xsteps]
       ysteps = eval[ysteps]
       pscale = eval[pscale]
    }
%>

<BODY>
  <H1>Interval Graph</H1>
  <P>
  <FORM ACTION="simplegraph.fsp" METHOD="get">
   Equation: <INPUT TYPE="text" SIZE=60 NAME="func" VALUE="$func"><BR>
   x-axis:
     min:<INPUT TYPE="text" SIZE=5 VALUE="$xmin" NAME="xmin">
     max:<INPUT TYPE="text" SIZE=5 VALUE="$xmax" NAME="xmax">
     steps:<INPUT TYPE="text" SIZE=5 VALUE="$xsteps" NAME="xsteps"><BR>
   y-axis:
     min <INPUT TYPE="text" SIZE=5 VALUE="$ymin" NAME="ymin">
     max <INPUT TYPE="text" SIZE=5 VALUE="$ymax" NAME="ymax">
     steps:<INPUT TYPE="text" SIZE=5 VALUE="$ysteps" NAME="ysteps"><BR>
   pixel subscaling: <INPUT TYPE="text" SIZE="5" VALUE="$pscale" NAME="pscale">
   <INPUT TYPE="SUBMIT">
  </FORM>
  </P>
  <P>
   <TT>

<%     // This section performs the actual graphing.  Tiny, isn't it?

if func
{
   func =~ %s/=/ PEQ /            // Replace = with possibly equals

   xstep = (xmax-xmin) / xsteps
   ystep = (ymax-ymin) / ysteps
   xscale = xstep * pscale
   yscale = ystep * pscale

   for yy=ymax to ymin step -ystep
   {
      y = new interval[yy, yy+yscale]
      for xx=xmin to xmax step xstep
      {
         x = new interval[xx, xx+xscale]

         res = eval[func]
         if res
            print["""<SPAN TITLE="$x, $y">X</SPAN>"""]
         else
            if res == false
               print["."]
            else
               print["!"]    // Evaluation problem (probably divide by zero)
      }
      println["<BR>"]
   }
}
%>

</TT>
</P>
  <HR>
  <P>
   This page uses <A HREF="/frinkdocs/#IntervalArithmetic">Interval
   Arithmetic</A> techniques in <A HREF="/frinkdocs/">Frink</A> to graph
   arbitrary equations that would be very difficult otherwise.  This is
   amazingly powerful and subtle, but the code is incredibly simple!  You
   should <A HREF="highlight.fsp?f=simplegraph.fsp">view the source</A>
   of this page to see how little code it actually takes!
  </P>
  <P>
   <I><A HREF="mailto:eliasen@mindspring.com">Alan Eliasen</A></I> was born
   <%= round[now[] - #1969-08-19 04:54 PM Mountain#, minute] -> ["days", "hours", "minutes"] %> ago.
  </P>

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   Back to <A HREF="/frinkdocs/fspdocs.html">Frink Server Pages
    documentation.</A>
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simplegraph.fsp - Frink Server Pages highlighter