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Problem with 'switch' statement

Started by Koen VB Dec 18, 2002 at 1:04 PM 5 replies 200+ views

Original Post

Dec 18, 2002 at 1:04 PM

Hi, I''m writing a breakout clone and I have some problems with a switch statement. This is the function that causes the problems: void TBreakout::UpdateGrid(int R, int C) { switch (Grid[R][C]) { case 1: Grid[R][C] = 0; break; case 2: Grid[R][C] = 0; break; case 3: Grid[R][C] = 0; break; case 4: Grid[R][C] = 5; break; case 5: Grid[R][C] = 6; break; case 6: Grid[R][C] = 7; break; case 7: Grid[R][C] = 8; break; case 8: Grid[R][C] = 0; break; case 9: Grid[R][C] = 0; break; } } The grid cells contain the type of block. 0 is empty, 1 to 3 are colored blocks, 4 to 8 are blocks with cracks in them that become larger and 9 is an exploding block. The effect should be that if you hit a block with cracks, they become bigger until the block is destroyed (wich should take 5 hits). The problem is that the blocks are always destroyed immediately. So if I hit a block with index 4, the index should become 5 and not 0. It seems like the rest of the switch statement is executed regardless of the break statement. Any suggestions on how to solve this? --------- http://users.pandora.be/koen.van.baelen ---------

ISOPimp

Dec 18, 2002 at 1:17 PM

Im pretty sure that is because after say Case 4: the grid is now equal to 5, then it goes to the next statement which is Case 5: which is also true, so it changes the grid to equal 6, and so on.

what about

  
void TBreakout::UpdateGrid(int R, int C)
{
	if((Grid[R][C] > 0 && Grid[R][C] < 4) || Grid[R][C] == 9)
	{
		Grid[R][C] = 0;
	}
	else if(Grid[R][C] >=4 && Grid[R][C] < 9)
	{
		Grid[R][C]++;
	}
	else
	{
		//Handle unexpected call

	}
}

davepermen

160

davepermen

Dec 18, 2002 at 1:25 PM

assuming the grid value type is int..

  
void TBreakout::UpdateGrid(int R, int C)
{
	const int updateValue[] = { -1,0,0,5,6,7,8,0,0 };
	Grid[R][C] = updateValue[Grid[R][C]];
	// or, as you can shift the index, you don''t need the -1 at the zero position..

	const int updateValue[] = { 0,0,5,6,7,8,0,0 };
	Grid[R][C] = updateValue[Grid[R][C]-1];
}

i love small lookuptables for stuff like this..

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Koen VB

Author

Koen VB

Dec 18, 2002 at 1:38 PM

Hi,
I''ve solved the problem. The UpdateGrid function was executed more than once if a collision occurred.

---------
http://users.pandora.be/koen.van.baelen
---------

Stan100

Dec 18, 2002 at 3:50 PM

Regarding the switch statement...
Can I use or|| in a switch statement?
case ''r'' || ''R'':
{
//
}
Or can you only use one statement?

Beatles are the best!

Plasmadog

Dec 18, 2002 at 4:06 PM

quote:
Original post by Stan100
Regarding the switch statement...
Can I use or|| in a switch statement?
case ''r'' || ''R'':
{
//
}
Or can you only use one statement?

I don''t think so. But if you are looking for a way to shorten your switch block you could do this:
void TBreakout::UpdateGrid(int R, int C)
{
switch (Grid[R][C])
{
case 1:
case 2:
case 3:
case 8:
case 9:
Grid[R][C] = 0;
break;
case 4:
case 5:
case 6:
case 7:
Grid[R][C]++;
break;
}
}

Plasmadog

Dec 18, 2002 at 4:11 PM

Or alternatively:

void TBreakout::UpdateGrid(int R, int C)
{
switch (Grid[R][C])
{
case 4:
case 5:
case 6:
case 7:
Grid[R][C]++;
break;
default:
Grid[R][C] = 0;
break;
}
}

Or even better:
void TBreakout::UpdateGrid(int R, int C)
{
if ( (Grid[R][C] >= 4) && (Grid[R][C] <= 7) )
Grid[R][C]++;
else
Grid[R][C] = 0;
}

[edited by - Plasmadog on December 18, 2002 5:13:01 PM]

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