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Map array probems?

Started by _damN_ Mar 19, 2009 at 12:07 PM 6 replies 1.4k views

Original Post

Mar 19, 2009 at 12:07 PM

Hi there! Im having trouble with my map array and have a few questions. This might be a bit tricky to explain so please bare with me! ;-) Basically i have a map array like so... #define MAP_WIDTH 16 #define MAP_HEIGHT 16 m_iIsoMap[MAP_WIDTH][MAP_HEIGHT]; I want MAP_WIDTH and MAP_HEIGHT to be able to hold the dimensions of the map. Is there a way for me to use a different kind of subscript, like int's? So the code would look something like this: int m_iWidth; int m_iHeight; m_iIsoMap[m_iWidth][m_iHeight]; But when i do it like that i get alot of errors because the arent constants. I wanto be able to do it that way because i wanto be able to just call a function simmilar to "SetMapSize(int iWidth,int iHeight) to set the maps size. So basically i just wanto be able to change the size of the map without having to use a pre-determined size. Can anybody think of a way i can do this, or a simmilar way. Any advice or ideas are welcome... I hope it makes sense ;-/ Thanks!

Dolf

Mar 19, 2009 at 12:21 PM

If you want to resize it, you could create a map on the heap with the "new" operator.

Or you could create a vector of vectors.

something like this:

// A 2d array on the heap, don't forget to delete it ^_^YourMapType* m_pMap = new YourMapType[m_iWidth][m_iHeight];// the vector versionstd::vector< std::vector< YourMapType > > m_map;

I hope that helped Mister _damN_.

fastcall22

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747

fastcall22

Mar 19, 2009 at 2:57 PM

Quote:
Original post by Dolf
*** Source Snippet Removed ***

Just a minor correction/expansion on what Dolf said:

// Allocateint* mMapArray = new int[ mWidth * mHeight ];// UsagemMapArray[ y * mWidth + x ] = 0; // Make sure y * mWidth + x is inside the array!// Deallocatedelete[] mMapArray;

// Allocate:int** mMapArray = new int*[ mHeight ];for ( int i = 0; i < mHeight; ++i )	mMapArray = new int[ mWidth ];	// UsagemMapArray[y][x] = 0; // Make sure y and x are inside the array!// Deallocatefor ( int i = 0; i < mHeight; ++i )	delete[] mMapArray;delete[] mMapArray;

// Allocateusing std::vector;vector<vector<int>> mMapArray( mHeight, vector<int>( mWidth, 0 ) );// UsagemMapArray[y][x] = 0; // vector will check bound for you !// Deallocate// vector will deallocate for you!

Dolf

Mar 19, 2009 at 4:09 PM

Haha yes ofcourse sorry about that with the 2d array on the heap.

Something like this can add in the asserts, and you can add functionality to your map.

#include "stdio.h"#include "assert.h"template< typename T >class MapArray{public:	MapArray( T width, T height )	:	m_width( width ),	m_height( height )	{		assert( width > 0 );		assert( height > 0 );		m_elements = new T[ width * height ];	}	~MapArray()	{		delete m_elements;	}	// should be replaced with operator overloading? :P	T Get( int x, int y ) const	{		assert( x >= 0 && x < m_width );		assert( y >= 0 && y < m_height );		return m_elements[ x + y * m_width ];	}	// should be replaced with operator overloading? :P	void Set( int x, int y, T& value )	{		assert( x >= 0 && x < m_width );		assert( y >= 0 && y < m_height );		m_elements[ y * m_width + x ] = value;	}	int GetWidth()	const	{ return m_width; }	int GetHeight() const	{ return m_height; }private:	T* m_elements;	int m_width;	int m_height;};int main() {	MapArray<int> map( 10, 10 );	// fill the map with K	int k = 0;	for ( int i = 0; i < map.GetWidth(); ++i )	{		for ( int j = 0; j < map.GetHeight(); ++j )		{			map.Set( i, j, k );			k++;		}	}	// print out the entire map, could make this a member of the class	for ( int i = 0; i < map.GetWidth(); ++i )	{		for ( int j = 0; j < map.GetHeight(); ++j )		{			printf( "X: %i, Y: %i, Value: %i \n", i, j, map.Get( i, j ) );		}	}	getchar();	return 1;}

[Edited by - Dolf on March 19, 2009 4:09:47 PM]

fastcall22

Mod

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fastcall22

Mar 19, 2009 at 5:33 PM

Right. With subscript operators, would look something like this:

	const Type& operator() ( int x, int y ) const	{			assert( CheckBounds( x, y ) );				return mData[ y * mWidth + x ];	}			Type& operator() ( int x, int y )	{		assert( CheckBounds( x, y ) );		return mData[ y * mWidth + x ];	}

Subscript operators come in pairs

_damN_

Author

_damN_

Mar 20, 2009 at 9:13 AM

Thanks guys, i learned alot from this. did also some more research on dynamic arrays etc. i got a couple of ideas how to implement it.

MANY THANKS! -_-

Zahlman

257

Zahlman

Mar 20, 2009 at 6:35 PM

Quote:
Original post by _damN_
Hi there!

Im having trouble with my map array and have a few questions.
This might be a bit tricky to explain so please bare with me! ;-)

I know you can't see me via the GDNet forum, but I'd rather bear with you. :)

Quote:
Basically i have a map array like so...

#define MAP_WIDTH 16
#define MAP_HEIGHT 16

Don't use #define to create constants. Use real constants, e.g. 'const int MAP_WIDTH = 16;'.

Quote:
Is there a way for me to use a different kind of subscript, like int's?

16 is an integer value. :) But since what you want to do is set the size of the array at runtime: don't build it yourself as suggested here. Instead, use boost::multi_array.

Dolf

Mar 21, 2009 at 12:36 PM

Quote:
Original post by Zahlman
don't build it yourself as suggested here. Instead, use boost::multi_array.

Depends Zahlman, he mentioned he learned something.

If you are working on a project and you want to be as productive as possible and it's your call whether to include a particular library or not, you might want use it.

If you are learning C++, you might not.

Ofcourse it's good that you mention that there is an alternative, the more choice the better.

Cheers,

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