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• Using Divide and Conquer

  agp.cooper • 06/02/2019 at 10:27 • 2 comments

  Using Divide and Conquer

  Instead of a single hard coded procedure, use some intelligent sub-routines (i.e. procedures).

  What am I talking about? My BoxMaker code terrible. It is 800 lines long, hard coded and took forever to write and test.

  Intelligent code would be code that progressively breaks the problem down into sub-problems. Sub-problems are always easy to code and debug.

  Okay, here is the new and very short "makeBox" procedure (not yet fully featured but a start):

  static void makeBox(FILE *F1,char *LayerName,int LayerColour,double Length,double Width,double Height,double XOffset,double YOffset,bool Direction,double Tab,double Flange)
  {
    makeSquare(F1,LayerName,LayerColour,XOffset               ,YOffset         , Width,Length,Direction,-Tab,-Tab,Flange); // Top  #1 - Slot/Slot
    makeSquare(F1,LayerName,LayerColour,3*XOffset+Width       ,YOffset         ,Height,Length,Direction, Tab,-Tab,   0.0); // Side #1 - Slot/Tab
    makeSquare(F1,LayerName,LayerColour,5*XOffset+Width+Height,YOffset         ,Height, Width,Direction, Tab, Tab,   0.0); // End  #1 - Tab/Tab
    makeSquare(F1,LayerName,LayerColour,XOffset               ,YOffset*3+Length, Width,Length,Direction,-Tab,-Tab,Flange); // Top  #2 - Slot/Slot
    makeSquare(F1,LayerName,LayerColour,3*XOffset+Width       ,YOffset*3+Length,Height,Length,Direction, Tab,-Tab,   0.0); // Side #2 - Slot/Tab
    makeSquare(F1,LayerName,LayerColour,5*XOffset+Width+Height,YOffset*3+Length,Height, Width,Direction, Tab, Tab,   0.0); // End  #2 - Tab/Tab
  }

  So what does it do? It creates six squares that represent the sides of the box, like this:

  But to create those squares it has to call a "makeSquare" procedure:

  static void makeSquare(FILE *F1,char *LayerName,int LayerColour,double XStart,double YStart,double Width,double Height,bool Direction,double TabX,double TabY,double Flange)
  {
    DXF_PolylineBegin(F1,LayerName,LayerColour);
    if (Direction) { // Clockwise
      makeLine(F1,LayerColour,XStart      ,YStart       ,XStart      ,YStart+Height,Direction,TabX,Flange);
      makeLine(F1,LayerColour,XStart      ,YStart+Height,XStart+Width,YStart+Height,Direction,TabY,Flange);
      makeLine(F1,LayerColour,XStart+Width,YStart+Height,XStart+Width,YStart       ,Direction,TabX,Flange);
      makeLine(F1,LayerColour,XStart+Width,YStart       ,XStart      ,YStart       ,Direction,TabY,Flange);
    } else {         // Anti-clockwise
      makeLine(F1,LayerColour,XStart      ,YStart       ,XStart+Width,YStart       ,Direction,TabY,Flange);
      makeLine(F1,LayerColour,XStart+Width,YStart       ,XStart+Width,YStart+Height,Direction,TabX,Flange);
      makeLine(F1,LayerColour,XStart+Width,YStart+Height,XStart      ,YStart+Height,Direction,TabY,Flange);
      makeLine(F1,LayerColour,XStart      ,YStart+Height,XStart      ,YStart       ,Direction,TabX,Flange);
    }
    DXF_PolylineEnd(F1);
  }

  And makeSquare calls makeLine, that makes lines with "tabs", like this:

  You may have noticed TabX and TabY options in the code. This allow me to swap the tab direction as in the case of the second (or middle) square (above).

  The "makeLine" code is a little more complicated:

  static void makeLine(FILE *F1,int LayerColour,double xstart,double ystart,double xend,double yend,bool Direction,double Tab,double Flange)
  {
    double dl,dx,dy,x1,y1,x2,y2;
    ezx_color_t Clr=GetClr(LayerColour);
  
    dx=xend-xstart;
    dy=yend-ystart;
    dl=sqrt(dx*dx+dy*dy);
  
    if ((Flange<=0.0)||(Tab>0.0)) {
      // No Flange Case
      x1=xstart;
      y1=ystart;
      x2=xstart+dx/4;
      y2=ystart+dy/4;
      ezx_line_2d(disp,(int)(scale*x1),height-(int)(scale*y1),(int)(scale*x2),height-(int)(scale*y2),&Clr,1);
      DXF_PolylinePoint(F1,x1,y1,0.0);
      DXF_PolylinePoint(F1,x2,y2,0.0);
  
      x1=x2;
      y1=y2;
      if (Direction) {
        x2=x1-Tab*dy/dl;
        y2=y1+Tab*dx/dl;
      } else {
        x2=x1+Tab*dy/dl;
        y2=y1-Tab*dx/dl;
      }
      ezx_line_2d(disp,(int)(scale*x1),height-(int)(scale*y1),(int)(scale*x2),height-(int)(scale*y2),&Clr,1);
      DXF_PolylinePoint(F1,x2,y2,0.0);
  
      x1=x2;
      y1=y2;
      x2=x1+dx/4;
      y2=y1+dy/4;
      ezx_line_2d(disp,(int)(scale*x1),height-(...

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