improve comments

pub/src/dualplot.cpp

@@ -27,28 +27,31 @@ CPlot::CPlot( uint _iPlot, bool _logx, bool _logy ) :
     iPlot( _iPlot ), X( _logx ), Y( _logy ),
     maxpoints(20000), with_errors(true), equipoints(7), refine(true)
 {
-    // Start gnuplot. Use input redirection so that gnuplot receives
-    // commands from a gp_fifo which is created here.
+    // == Initialization for Gnuplot ==
 
+    // Create a named pipe (FIFO) that will transmit our commands to Gnuplot.
     string fn_fifo = string("/tmp/gnuplot-") + getenv( "LOGNAME" );
-
     mystd::system( "rm -f "+fn_fifo );
     if (mkfifo( fn_fifo.c_str(), 0666 ))
         throw "SYSTEM ERROR cannot make fifo " + fn_fifo +
             ": will not be able to print";
 
+    // Start a Gnuplot that will read from our pipe.
     mystd::system( "gnuplot -title " + strg(iPlot) + " -noraise" +
                    " < " + fn_fifo + " &" );
 
-    // we use open instead of fopen or ofstream,
-    // because we need non-blocking mode.
+    // Open our pipe so that we can write commands to it
+    //   (we use 'open' instead of 'fopen' or 'ofstream',
+    //    because we need non-blocking mode).
     if ( ! ( gp_fifo = open( fn_fifo.c_str(), O_WRONLY ) ) )
         throw "SYSTEM ERROR cannot open fifo " + fn_fifo +
             ": will not be able to print";
     fcntl( gp_fifo, F_SETFL, O_NONBLOCK );
 
+    // Now the initialization _within_ Gnuplot.
     gp_write( string("set terminal x11") );
 
+    // == Initialization for PostScript ==
     ps_fnum=0;
 }