Programming Forums > Application Development > C++

The Dark · Nov 30th, 2006, 7:26 PM

Nope, you can't delete the actual m_robots and m_sources arrays because they are not allocated using new (they are allocated as part of the Valley class, so they don't need to be deleted individually). What you need to do is loop through the arrays and delete each individual entry, because those were allocated individually.

aznballerlee · Nov 30th, 2006, 7:41 PM

Okay, thanks for clarifying this. I'm on the right track. Just a few more tasks I believe.

Next task I tried to do, but can't think of how, is the step function. I think knowing this would help me think of ideas for other functions:

I'm on bool Robot::step().

(Toggle Plain Text)

bool Robot::step()
{
	// If the robot has no energy left, return false
	// if (FULL_ENERGY == 0)
	//	return false;
	
       // Otherwise,
	else
	{	
		//    Randomly change direction with probability 1/3
		if (rand() % 3 == 0)    // 1/3 probability to pick a direction
			m_dir = Dir(rand() % 4);    // pick a random direction
		
	        //    Attempt to move one step in the direction we're currently facing.
		//      (E.g., to move north, decrement the row coordinate.)  If we can't
		//      move in that direction, don't move.
               if (r < 0  ||  r >= NROWS  ||  c < 0  ||  c >= NCOLS)
	    {
		cout << "***** Robot created with invalid coordinates (" << r << ","
			<< c << ")!" << endl;
		exit(1);
	    }
		switch (m_dir)
		{
		case NORTH:
			// TODO: Move one step north, if possible.
                        r--;
			break;
		case SOUTH:
                        r++;
		case WEST:
                        c++;
		case EAST:
                        c--;

The stuff I did was in blue. Can you tell me if I'm on the right track?
EDIT: Compiling said that r and c are undeclared! What must I do to use them?

The Dark · Nov 30th, 2006, 8:11 PM

To check energy levels you need to look at the m_energy variable.
To get the current position of the robot, you need to look at m_row and m_col.
What you have for the moves is right as far as it goes - you also need to check whether the move would put the robot out of bounds. If so, you should just return before changing the position.

Also note that, traditionally, WEST is left (c--) and EAST is right (c++).

Once you have done the move, follow the rest of the robot step instructions.

aznballerlee · Nov 30th, 2006, 8:17 PM

Okay, the code works now! I'll do the rest of the step function now.

EDIT:
I continued, tried, played around, and got stuck once again.

(Toggle Plain Text)

       //    The attempt to move consumes one unit of energy.
      //    If as a result of the attempt to move, the robot is at an energy
      //       source, it's recharged to the FULL_ENERGY level.
	m_energy--;
	if (m_sources[m_nsources] = new EnergySource(r,c))
		m_energy = FULL_ENERGY;
	
	//    If at this spot there's another robot whose energy level is 0,
	//       then if we have at least SHARE_THRESHHOLD units of energy,
	//       transfer SHARE_AMOUNT units to that other robot.  (If there
	//       are two or more dead robots here, we donate to only one.)
	//    Return true, indicating the robot attempted to move.
      	else if (// another robot's energy is 0)
		if (m_energy > SHARE_THRESHHOLD)
			// that robot's energy = SHARE_AMOUNT

		return true;

}

I don't know what to stick in the parts I // out.

aznballerlee · Nov 30th, 2006, 9:24 PM

Actually, I don't know why I put these lines, they're completely wrong:

(Toggle Plain Text)

if (m_sources[m_nsources] = new EnergySource(r,c))
		m_energy = FULL_ENERGY;

Using this made no difference, still error:

(Toggle Plain Text)

if (EnergySource(m_row, m_col)

I also tried the accessor for the Valley class:

(Toggle Plain Text)

bool energySourceAt(int r, int c) const
//      If there is an energy source at coordinates (r,c), return true;
//      otherwise, return false.
{
	if (EnergySource(r,c))
		return true;
	else
		return false;
}

For this, I once again got compilation errors.

The Dark · Nov 30th, 2006, 10:08 PM

In the robot step method, you need to call the energySourceAt accessor for the valley object for this robot, to determine if there is an energy source at the current location.

You also need to write the energySourceAt accessor. The Valley class has an array of energy sources - you need to look through that array to see if there is one at the current coordinates.

aznballerlee · Nov 30th, 2006, 10:24 PM

Quote:

In the robot step method, you need to call the energySourceAt accessor for the valley object for this robot, to determine if there is an energy source at the current location.

You are right, I was thinking about that too.

(Toggle Plain Text)

if (energySourceAt(r,c))
       m_energy = FULL_ENERGY;

Quote:

You also need to write the energySourceAt accessor

Here's my problem, it doesn't compile:

(Toggle Plain Text)

bool energySourceAt(int r, int c) const
//      If there is an energy source at coordinates (r,c), return true;
//      otherwise, return false.
{
	if (EnergySource(r,c))
		return true;
	else
		return false;
}

Quote:

The Valley class has an array of energy sources - you need to look through that array to see if there is one at the current coordinates.

(Toggle Plain Text)

if (m_sources[MAXSOURCES] =EnergySource(m_row, m_col))

EDIT: Ahh, this doesn't work.

The Dark · Nov 30th, 2006, 10:45 PM

Quote:

Originally Posted by aznballerlee

You are right, I was thinking about that too.
[code]
Here's my problem, it doesn't compile:

(Toggle Plain Text)

bool energySourceAt(int r, int c) const
//      If there is an energy source at coordinates (r,c), return true;
//      otherwise, return false.
{
	if (EnergySource(r,c))
		return true;
	else
		return false;
}

You need to take a step back and try to work out what you want the energySourceAt method to do, before throwing code at it.

Write down a list of steps, in English, of how the energySourceAt method could check whether there is an energy source at a particular location. Dont even worry about where the list is, just pretend you have a pile of pieces of paper with an energy location on each one, how would you go about finding whether a given location had an energy source.

The code you have at the moment just creates an EnergySource object inside the test of an if statement.

Quote:

Originally Posted by aznballerlee

(Toggle Plain Text)

if (m_sources[MAXSOURCES] = energySourceAt(m_row, m_col))

For one line, responding to "look through the array" you have a lot of problems:
- I'm not even sure where you were thinking of putting that code. If it is inside the energySourceAt method, then it will be infinitely recursive. If you were going to put it in the Robot step method, then Robot doesn't have an m_sources or and energySourceAt function.
- m_sources[MAXSOURCES] is outside the boundaries of m_sources, which may cause a crash.
- You shouldn't be doing an assignment inside an if test expression
- energySourceAt returns a boolean, you can't compare that with a pointer to an energySource.
- To look through an array you need a loop.

aznballerlee · Nov 30th, 2006, 10:54 PM

Quote:

Write down a list of steps, in English, of how the energySourceAt method could check whether there is an energy source at a particular location. Dont even worry about where the list is, just pretend you have a pile of pieces of paper with an energy location on each one, how would you go about finding whether a given location had an energy source.

1. Check location of robot.
2. At wherever location, check the 'piece of paper'.
3. If that 'piece of paper' has an energy source, succeed.
4. Otherwise, fail.

Quote:

For one line, responding to "look through the array" you have a lot of problems:
- I'm not even sure where you were thinking of putting that code. If it is inside the energySourceAt method, then it will be infinitely recursive. If you were going to put it in the Robot step method, then Robot doesn't have an m_sources or and energySourceAt function.
- m_sources[MAXSOURCES] is outside the boundaries of m_sources, which may cause a crash.
- You shouldn't be doing an assignment inside an if test expression
- energySourceAt returns a boolean, you can't compare that with a pointer to an energySource.
- To look through an array you need a loop.

This is inside the Valley. Anyways, still stuck on what to do. I started a loop ..

(Toggle Plain Text)

for (int k = 0; k < MAXSOURCES; k++_
{
   if ( array element has energy source  )
//  return true;
   else
     return false;
}

Earlier, you said this:

Quote:

You also need to write the energySourceAt accessor. The Valley class has an array of energy sources - you need to look through that array to see if there is one at the current coordinates.

but you're saying I can't use m_sources[m_nsources]. Confused.

The Dark · Nov 30th, 2006, 11:07 PM

Quote:

Originally Posted by aznballerlee

1. Check location of robot.
2. At wherever location, check the 'piece of paper'.
3. If that 'piece of paper' has an energy source, succeed.
4. Otherwise, fail.

1. OK the location is given to you in the parameters of energySourceAt, so forget about the robot for a bit.
2. You need to break this step down - how do you know which piece of paper in the pile you need to look at?
3. Yep, except don't forget you might not find a piece of paper for the location you are after - you only have a piece of paper for each energy source, not each location. So its more like "if you find a piece of paper with the right location, succeed".
4. That's right.

Nov 30th, 2006, 7:41 PM	#22
aznballerlee Hobbyist Programmer Join Date: Nov 2006 Posts: 111 Rep Power: 2	Okay, thanks for clarifying this. I'm on the right track. Just a few more tasks I believe. Next task I tried to do, but can't think of how, is the step function. I think knowing this would help me think of ideas for other functions: I'm on bool Robot::step(). (Toggle Plain Text) bool Robot::step() { // If the robot has no energy left, return false // if (FULL_ENERGY == 0) // return false; // Otherwise, else { // Randomly change direction with probability 1/3 if (rand() % 3 == 0) // 1/3 probability to pick a direction m_dir = Dir(rand() % 4); // pick a random direction // Attempt to move one step in the direction we're currently facing. // (E.g., to move north, decrement the row coordinate.) If we can't // move in that direction, don't move. if (r < 0 \|\| r >= NROWS \|\| c < 0 \|\| c >= NCOLS) { cout << "*** Robot created with invalid coordinates (" << r << "," << c << ")!" << endl; exit(1); } switch (m_dir) { case NORTH: // TODO: Move one step north, if possible. r--; break; case SOUTH: r++; case WEST: c++; case EAST: c--; bool Robot::step() { // If the robot has no energy left, return false // if (FULL_ENERGY == 0) // return false; // Otherwise, else { // Randomly change direction with probability 1/3 if (rand() % 3 == 0) // 1/3 probability to pick a direction m_dir = Dir(rand() % 4); // pick a random direction // Attempt to move one step in the direction we're currently facing. // (E.g., to move north, decrement the row coordinate.) If we can't // move in that direction, don't move. if (r < 0 \|\| r >= NROWS \|\| c < 0 \|\| c >= NCOLS) { cout << "* Robot created with invalid coordinates (" << r << "," << c << ")!" << endl; exit(1); } switch (m_dir) { case NORTH: // TODO: Move one step north, if possible. r--; break; case SOUTH: r++; case WEST: c++; case EAST: c--; The stuff I did was in blue. Can you tell me if I'm on the right track? EDIT: Compiling said that r and c are undeclared! What must I do to use them?** Last edited by aznballerlee; Nov 30th, 2006 at 8:14 PM. Reason: indenting

Nov 30th, 2006, 8:17 PM	#24
aznballerlee Hobbyist Programmer Join Date: Nov 2006 Posts: 111 Rep Power: 2	Okay, the code works now! I'll do the rest of the step function now. EDIT: I continued, tried, played around, and got stuck once again. (Toggle Plain Text) // The attempt to move consumes one unit of energy. // If as a result of the attempt to move, the robot is at an energy // source, it's recharged to the FULL_ENERGY level. m_energy--; if (m_sources[m_nsources] = new EnergySource(r,c)) m_energy = FULL_ENERGY; // If at this spot there's another robot whose energy level is 0, // then if we have at least SHARE_THRESHHOLD units of energy, // transfer SHARE_AMOUNT units to that other robot. (If there // are two or more dead robots here, we donate to only one.) // Return true, indicating the robot attempted to move. else if (// another robot's energy is 0) if (m_energy > SHARE_THRESHHOLD) // that robot's energy = SHARE_AMOUNT return true; // The attempt to move consumes one unit of energy. // If as a result of the attempt to move, the robot is at an energy // source, it's recharged to the FULL_ENERGY level. m_energy--; if (m_sources[m_nsources] = new EnergySource(r,c)) m_energy = FULL_ENERGY; // If at this spot there's another robot whose energy level is 0, // then if we have at least SHARE_THRESHHOLD units of energy, // transfer SHARE_AMOUNT units to that other robot. (If there // are two or more dead robots here, we donate to only one.) // Return true, indicating the robot attempted to move. else if (// another robot's energy is 0) if (m_energy > SHARE_THRESHHOLD) // that robot's energy = SHARE_AMOUNT return true; } I don't know what to stick in the parts I // out.

Nov 30th, 2006, 9:24 PM	#25
aznballerlee Hobbyist Programmer Join Date: Nov 2006 Posts: 111 Rep Power: 2	Actually, I don't know why I put these lines, they're completely wrong: (Toggle Plain Text) if (m_sources[m_nsources] = new EnergySource(r,c)) m_energy = FULL_ENERGY; if (m_sources[m_nsources] = new EnergySource(r,c)) m_energy = FULL_ENERGY; Using this made no difference, still error: (Toggle Plain Text) if (EnergySource(m_row, m_col) if (EnergySource(m_row, m_col) I also tried the accessor for the Valley class: (Toggle Plain Text) bool energySourceAt(int r, int c) const // If there is an energy source at coordinates (r,c), return true; // otherwise, return false. { if (EnergySource(r,c)) return true; else return false; } bool energySourceAt(int r, int c) const // If there is an energy source at coordinates (r,c), return true; // otherwise, return false. { if (EnergySource(r,c)) return true; else return false; } For this, I once again got compilation errors. Last edited by aznballerlee; Nov 30th, 2006 at 9:40 PM.

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Nov 30th, 2006, 7:26 PM	#21
The Dark Expert Programmer Join Date: Jun 2005 Posts: 850 Rep Power: 4	Nope, you can't delete the actual m_robots and m_sources arrays because they are not allocated using new (they are allocated as part of the Valley class, so they don't need to be deleted individually). What you need to do is loop through the arrays and delete each individual entry, because those were allocated individually.

Nov 30th, 2006, 8:11 PM	#23
The Dark Expert Programmer Join Date: Jun 2005 Posts: 850 Rep Power: 4	To check energy levels you need to look at the m_energy variable. To get the current position of the robot, you need to look at m_row and m_col. What you have for the moves is right as far as it goes - you also need to check whether the move would put the robot out of bounds. If so, you should just return before changing the position. Also note that, traditionally, WEST is left (c--) and EAST is right (c++). Once you have done the move, follow the rest of the robot step instructions.

Nov 30th, 2006, 10:08 PM	#26
The Dark Expert Programmer Join Date: Jun 2005 Posts: 850 Rep Power: 4	In the robot step method, you need to call the energySourceAt accessor for the valley object for this robot, to determine if there is an energy source at the current location. You also need to write the energySourceAt accessor. The Valley class has an array of energy sources - you need to look through that array to see if there is one at the current coordinates.

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