OpenEuphoria

Re: Case/switch

• Posted by Derek Parnell <ddparnell at bigpond.com> Feb 15, 2002
• 442 views

----- Original Message -----
From: "SR.Williamson" <writeneu at hotmail.com>
To: "EUforum" <EUforum at topica.com>
Subject: Case/switch


>
> Kat brought up case/switch. I'd love to see this become part of the
> language.
>
> I was writing an artificial life program for Windows. Basically, it was
> a bunch of buttons in a grid. If a button was "hot", the program would
> check to see whether the button in the row above and to either side was
> "hot" to determine whether to make that button itself "hot".
>
> Well, as you can imagine, that works fine for the buttons in the middle
> of the grid. But when you get to the buttons in the grid above, you have
> to check to see if a button is at a window edge. So there are a lot of
> "if button1 = leftedge or button2 = rightedge" kind of stuff. It got
> really tedious. The only think I could think was "This would be so much
> easier with a Case statement".
>
> Is there some easy way to do that that I'm missing?
>

As a general principle, I try to use a data-oriented programming style. In
the case (no pun intended) you describe, you could try something like
this...
 --------------
function doTopLeft( ... )
   . . .
end function
function doTop( ... )
   . . .
end function
function doTopRight( ... )
   . . .
end function
.
.
.
function doMiddle( ... )
  . . .
end function
constant TL = routine_id("doTopLeft"),
         TP = routine_id("doTop"),
         TR = routine_id("doTopRight"),
         .
         .
         .
         MD = routine_id("doMiddle")

-- For each button in the grid, you assign it's position handler.
-- Assuming you have a sequence holding the button ids and
-- another for the position property.

sequence GridBtns, GridPosns
GridBtns = repeat(0, ButtonCount)
GridPosn = repeat(0, ButtonCount)

for i = 1 to GridWidth do
  for j = 1 to GridHeight do
     if i = 1 then -- top row
         if j = 1 then
             x = TL -- top left
         elsif j = GridHeight then
             x = BL -- bottom left
         else
             x = LF -- left
         end if
     elsif i = GridWidth then
         if j = 1 then
             x = TR -- top right
         elsif j = GridHeight then
             x = BR -- bottom right
         else
             x = RT -- right
         end if
     else
         if j = 1 then
             x = TP -- top
         elsif j = GridHeight then
             x = BT -- bottom
         else
             x = MD -- middle
         end if
     end if
     -- Calc the index for the position.
     z = (j-1)* GridWidth + i
     GridPosn[z] = x
  next
next

-- Once this data is initialised, in the click handler do this.
procedure onClickBtn()
   integer b
   object rc

   b = find(getSelf(), GridBtns)
   rc = call_func( GridPosn[b], { . . .})
   .
   .
   .
end procedure
 -------

The idea is that you do a once-only set up of data that you can quickly use
during the running of your code. This is much quicker than making the
position decision everytime a button is pressed. This way, you only make
that decision once (so long as the button doesn't move).

cheers,
Derek