Tide gauges

    An array of Gauge structures passed to output_gauges() will create a file (called name) for each gauge. Each time output_gauges() is called a line will be appended to the file. The line contains the time and the value of each scalar in list in the cell containing (x,y). The desc field can be filled with a longer description of the gauge.

    typedef struct {
      char * name;
      double x, y;
      char * desc;
      FILE * fp;
    } Gauge;
    void output_gauges (Gauge * gauges, scalar * list)
      int n = 0;
      for (Gauge * g = gauges; g->name; g++, n++);
      coord a[n];
      n = 0;
      for (Gauge * g = gauges; g->name; g++, n++) {
        double xp = g->x, yp = g->y;
        unmap (&xp, &yp);
        a[n].x = xp, a[n].y = yp;
      int len = list_len(list);
      double v[n*len];
      interpolate_array (list, a, n, v, false);
      if (pid() == 0) {
        n = 0;
        for (Gauge * g = gauges; g->name; g++) {
          if (!g->fp) {
    	g->fp = fopen (g->name, "w");
    	if (g->desc)
    	  fprintf (g->fp, "%s\n", g->desc);
          if (v[n] != nodata) {
    	fprintf (g->fp, "%g", t);
    	for (scalar s in list)
    	  fprintf (g->fp, " %g", v[n++]);
    	fputc ('\n', g->fp);
    	fflush (g->fp);
    	n += len;