global L
link printf

procedure main()

    L := list(24, repl(" ", 78))
    L[5][5:10] := "-----"
    L[6][5] := "|"
    L[6][9] := "|"
    L[7][5] := "|"
    L[7][9] := "|"
    L[8][5:10] := "-----"
    i := ?["north","south","east","west"]
    northwall := 5
    southwall := 8
    westwall := 5
    eastwall := 9
    write("Let's add a door on the ", i, " wall.")
    if i == ("north"|"south") then {
       j := westwall + ? (eastwall-westwall-1)
       if i == "north" then { # insert a + into north wall
	  L[northwall][j] := "+"
          }
       else { # south
	  L[southwall][j] := "+"
          }
       }
    else { # east or west wall
       j := northwall + ? (southwall-northwall-1)
       if i == "east" then {
	  L[j][eastwall] := "+"
          }
       else {
	  L[j][westwall] := "+"
          }
      }
    
    show(L)
end

procedure show(L)
    every write(!L)
end