###################################################
   #                                                 #
   #  Lout keywords and @Code symbol.                #
   #                                                 #
   ###################################################

   def @Code right x
   { { Helvetica Base -1p } @Font lines @Break x }

   def @@BackEnd           { @Code "@BackEnd"           }
   def @@Begin             { @Code "@Begin"             }
   def @@Break             { @Code "@Break"             }
   def @@Case              { @Code "@Case"              }
   def @@Database          { @Code "@Database"          }
   def @@End               { @Code "@End"               }
   def @@Font              { @Code "@Font"              }
   def @@Char              { @Code "@Char"              }
   def @@Galley            { @Code "@Galley"            }
   def @@Graphic           { @Code "@Graphic"           }
   def @@HAdjust           { @Code "@HAdjust"           }
   def @@HContract         { @Code "@HContract"         }
   def @@HCover            { @Code "@HCover"            }
   def @@HExpand           { @Code "@HExpand"           }
   def @@HScale            { @Code "@HScale"            }
   def @@High              { @Code "@High"              }
   def @@HShift            { @Code "@HShift"            }
   def @@Include           { @Code "@Include"           }
   def @@Insert            { @Code "@Insert "           }
   def @@IncludeGraphic    { @Code "@IncludeGraphic"    }
   def @@Key               { @Code "@Key"               }
   def @@LClos             { @Code "@LClos"             }
   def @@LEnv              { @Code "@LEnv"              }
   def @@LInput            { @Code "@LInput"            }
   def @@LVis              { @Code "@LVis"              }
   def @@Moment            { @Code "@Moment"            }
   def @@Next              { @Code "@Next"              }
   def @@Null              { @Code "@Null"              }
   def @@OneCol            { @Code "@OneCol"            }
   def @@OneRow            { @Code "@OneRow"            }
   def @@Open              { @Code "@Open"              }
   def @@Outline           { @Code "@Outline"             }
   def @@PAdjust           { @Code "@PAdjust"           }
   def @@PrependGraphic    { @Code "@PrependGraphic"    }
   def @@Rotate            { @Code "@Rotate"            }
   def @@Scale             { @Code "@Scale"             }
   def @@SetColor          { @Code "@SetColor"          }
   def @@SetColour         { @Code "@SetColour"         }
   def @@Language          { @Code "@Language"          }
   def @@CurrLang          { @Code "@CurrLang"          }
   def @@Space             { @Code "@Space"             }
   def @@SysDatabase       { @Code "@SysDatabase"       }
   def @@SysInclude        { @Code "@SysInclude"        }
   def @@SysIncludeGraphic { @Code "@SysIncludeGraphic" }
   def @@SysPrependGraphic { @Code "@SysPrependGraphic" }
   def @@Tag               { @Code "@Tag"               }
   def @@Tagged            { @Code "@Tagged"            }
   def @@Use               { @Code "@Use"               }
   def @@VAdjust           { @Code "@VAdjust"           }
   def @@VContract         { @Code "@VContract"         }
   def @@VCover            { @Code "@VCover"            }
   def @@VExpand           { @Code "@VExpand"           }
   def @@VScale            { @Code "@VScale"            }
   def @@VShift            { @Code "@VShift"            }
   def @@Wide              { @Code "@Wide"              }
   def @@Yield             { @Code "@Yield"             }


   ###################################################
   #                                                 #
   #  Miscellaneous symbols used in the guide.       #
   #                                                 #
   ###################################################

   def @TeX
   { @OneCol { T &0.4fo {-0.2f @VShift E} &0.45fo X }
   }

   def @LaTeX
   { @OneCol { L &0.3fo { +0.1f @VShift 0.8f @Font A } &0.4fo @TeX }
   }

   import @BasicSetup
   def @Batlow { Batlow Food Distributors Pty. Ltd. }

   import @BasicSetup
   def @GreyBox right x { @Box paint { lightgrey } x }

   import @BasicSetup
   def @HeadingBox left x right y
   {
       @Box { @CentredDisplay @Heading x y }
   }

   def @FilledBox
   {
     @BackEnd @Case {
       PostScript @Yield {
         { "0 0 moveto xsize 0 lineto xsize ysize lineto 0 ysize lineto"
           "closepath fill"
         } @Graphic { 0.6f @High ^/ 0.4f @High 4f @Wide }
       }
       PDF @Yield {
         { "0 0 m __xsize 0 l __xsize __ysize l 0 __ysize l h f"
         } @Graphic { 0.6f @High ^/ 0.4f @High 4f @Wide }
       }
     }
   }

   import @Eq
   def epi { p sub i ` log sub 2 ` p sub i }
 
   import @Eq
   def ep right x { p sub x ` log sub 2 ` p sub x }
 
   def @Dbl left x right y
   { 1.95i @Wide
     { 1.25i @Wide { |1rt @Code x } |0.2i @Eq {non y} }
   }
 
   import @Eq
   def @ExA { 1 over sqrt { 1 - 4 x sup 2 } }

   def @@Diag { @Code "@Diag" }

   extend @DiagSetup @Diag
   macro @MyNode {
    @Node
	outline {
	    LR:: { xsize 0 }
	    LR:< 0d
	    UL:: { 0 ysize }
	    UL:< 270d
	    0 0 LR UL 0 0
	}
   }

   extend @DiagSetup @Diag
   macro @MyLink {
    @Link
	path {
	    FROM:: from
	    TO:: to
	    FROM TO
	}
   }

   def @ShowHMark right x
   {
      {
        "-0.3 cm ymark moveto xsize 0.3 cm add ymark lineto"
        "[ 0.1 cm ] 0 setdash stroke"
      } @Graphic x
   }
 
   def @ZeroWidth right x { @OneCol { |0io x |0io } }
 
   def @SomeText
   {
Johnson suddenly uttered, in a strong determined tone, an apophegm, at
which many will start:  `Patriotism is the last refuge of a scoundrel.'
   }
 
   import @DiagSetup
   def @OpenCircle { @Diag { @Circle margin { 0.2f } } }
 
   import @DiagSetup
   def @ClosedCircle { @Diag { @Circle paint { black } margin { 0.2f } } }
 
   import @TblSetup @BasicSetup
   def @AmberLight
   {
       @OneRow @Tbl
           aformat { @Cell indentvertical { align } A }
           marginhorizontal { 0i }
           marginvertical { 0i }
           strut { no }
           rule { no }
           paint { no }
        {
            @Rowa A { @OpenCircle }
            @MarkRowa A { @ClosedCircle }
            @Rowa A { @OpenCircle }
        }
   }

   import @DiagSetup @Diag
   def @Four named code { } right x
   {
       3.8c @Wide @Code code    ||0.3c
       2.7c @Wide @StartRight x ||0.3c
       2.7c @Wide @StartUp    x ||0.3c
       2.7c @Wide @StartLeft  x ||0.3c
       2.2c @Wide @StartDown  x
   }

   import @BasicSetup
   def @TextureSample right x
   {
      @Box margin { 0i }
      x @Texture @Box margin { 2.0f } paint { black } {}
   }

   import @BasicSetup
   def @XRGBTest right col
   {
      def @Thing {
	@HContract @VContract { 0.9c @Wide 0.5f @High ^/ 0.5f @High }
      }

      @HContract {
          @Box paint { @Xrgb col } margin { 0i } @Thing
          &0.2c
          2.8c @Wide downifneeded @Scale @Code col
      }
   }

   def @XRGBNoTest
   {
      @HContract { 0.9c @Wide &0.2c 2.8c @Wide {} }
   }