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plasma_state_off? or on?

Started by April 12, 2002 08:49 PM
1 comment, last by edwinnie 22 years, 7 months ago
i am using the WGPFD book. there is this function>
  void Fire_Plasma(int x,int y, int vel)
{
// this function fires a plasma pulse at the given starting

// position and velocity, of course, one must be free for 

// this to work


// scan for a pulse that is available

for (int index=0; index<MAX_PLASMA; index++)
    {
    // is this one available

      // test if plasma pulse is in flight

    if (plasma[index].state == PLASMA_STATE_OFF)
       {
       // start this one up

       plasma[index].x  = x;
       plasma[index].y  = y;
       plasma[index].yv = -vel;
       plasma[index].curr_frame = 0;
       plasma[index].state =  PLASMA_STATE_ON;
       
       // later

       return;

       } // end if


    } // end for


} // end Fire_Plasma  
i am kinda confused to what actualli happen, that is, which states r being triggered...heres my understanding...see if find any stuff i misunderstood... "Initially, the plasma state is "off". and we have #define PLASMA_STATE_OFF 0 #define PLASMA_STATE_ON 1 When spacebar is pressed, Fire_Plasma() starts. If index is 0, plasma[0].state is checked to see if it is in "off" state. It is in "off" state, so now plasma[0].state is switched "on". now in Init_Plasma()"
  void Init_Plasma(void)
{
// this function initializes and loads all the plasma 

// weapon pulses


// load the plasma imagery 

Load_Bitmap_File(&bitmap8bit, "PLASMA8.BMP");


#if 1
// now create and load each plasma pulse

for (int pulse=0; pulse<MAX_PLASMA; pulse++)
    {
    // create the bob to hold pulse

    Create_BOB(&plasma[pulse],0,0,16,24,6,
               BOB_ATTR_VISIBLE | BOB_ATTR_MULTI_FRAME,
               DDSCAPS_SYSTEMMEMORY);
 
    // load animation frames

    for (int frame=0; frame<6; frame++)
         Load_Frame_BOB(&plasma[pulse],&bitmap8bit,frame,frame,0,BITMAP_EXTRACT_MODE_CELL);  

    // set animation rate

    Set_Anim_Speed_BOB(&plasma[pulse],1);

    // set state to off

    plasma[pulse].state = PLASMA_STATE_OFF;

    } // end for pulse

#endif

#if 0
// create the first bob

Create_BOB(&plasma[0],0,0,16,24,6,
            BOB_ATTR_VISIBLE | BOB_ATTR_MULTI_FRAME,
            DDSCAPS_SYSTEMMEMORY);

// load animation frames

for (int frame=0; frame<6; frame++)
     Load_Frame_BOB(&plasma[0],&bitmap8bit,frame,frame,0,BITMAP_EXTRACT_MODE_CELL);  

// set animation rate

Set_Anim_Speed_BOB(&plasma[0],1);

// set state to off

plasma[0].state = PLASMA_STATE_OFF;

for (int pulse=1; pulse<MAX_PLASMA; pulse++)
    {
    memcpy(&plasma[pulse], &plasma[0], sizeof(BOB));
    } // end for pulse


#endif


// unload data infile

Unload_Bitmap_File(&bitmap8bit);

} // end Init_Plasma  
"so now [#if 1] from the Init_Plasma() starts, plasma[0].state will be switched "off". If MAX_PLASMA is 8, and all plasma[0-7] undergone [#if 1], and then their states are switched "off" towards the end of [#if 1]. If the spacebar is always pressed, i assume that Fire_Plasma() continue to occur." But why do we need [#if 0] in Init_Plasma()? Does it mean that the next set of 8 plasma pulses will be continued to fire by undergoing [#if 0], since the PLASMA_STATE_OFF is now in effect? (since Fire_Plasma() will set the attributes globally)
RTFM on the C preprocessor.

Code within a #if 0... #endif block will not even be compiled as the preprocessor silently cuts it off.

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Stolen from Magmai Kai Holmlor, who held it from Oluseyi, who was inspired by Kylotan...
"Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." — Brian W. Kernighan
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ya...that i noe...so what about it?

so what if i changed to "if statements" instead, like
if (PLASMA_STATE_OFF == 0) { }
?

[edited by - edwinnie on April 12, 2002 10:40:50 PM]

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