Problem with arrays, pointers and functions when combined

This is a discussion on Problem with arrays, pointers and functions when combined within the C++ Programming forums, part of the General Programming Boards category; Hi I've written a particle engine, and decided to try to simulate a cloth. Mostly because I want to test ...

  1. #1
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    Problem with arrays, pointers and functions when combined

    Hi
    I've written a particle engine, and decided to try to simulate a cloth. Mostly because I want to test the speed of C++ since I'm used to Flash but I also want to see if it's possible to use it in a game. Anyway, I got an array of particles and I want to pass that to a function which creates a cloth of them. Here's the code:

    Code:
    void createCloth(int numOfParticles, cParticle* particles[])
    {
    
    	cParticle* tPart;
    
    	for (int i=0; i < (int)sqrt((float)numOfParticles); i++)
    	{
    		for (int j=0; j < (int)sqrt((float)numOfParticles); j++)
    		{
    			tPart = particles[10*i+j];
    			tPart->init(j/10, i/10, 0, 0, 0, 0, 0.5);
    		}
    	}
    	for (int i=0; i < (int)sqrt((float)numOfParticles); i++)
    	{
    		for (int j=0; j < (int)sqrt((float)numOfParticles); j++)
    		{
    			tPart = particles[10*i+j];
    
    			if (j != 0)	tPart->addConstraint(&particles[i+j-1], 0.1, false);
    			if (j!= (int)sqrt((float)numOfParticles)-1) tPart->addConstraint(&particles[i+j+1], 0.1, false);
    			if (i != 0) tPart->addConstraint(&particles[10*i+j-10], 0.1, false);
    			if (i != (int)sqrt((float)numOfParticles)-1) tPart->addConstraint(&particles[10*i+j+10], 0.1, false);
    		}
    	}
    }
    
    //Heres the call for it, along with the array (in winMain function):
    
    cParticle particles[numParticles];
    createCloth(numParticles, &particles);
    I get the error:

    error C2664: 'createCloth' : cannot convert parameter 2 from 'cParticle (*__w64 )[100]' to 'cParticle *'

    I've tried anything I can think of, but nothing works. Anyone knows what might be wrong?

    Thanks in advance

    The Wazaa

  2. #2
    and the hat of wrongness Salem's Avatar
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    Arrays are always passed as pointers, so there is no need to point to the array just to be able to update it.

    So
    void createCloth(int numOfParticles, cParticle particles[])

    And
    createCloth(numParticles, particles);

    > for (int i=0; i < (int)sqrt((float)numOfParticles); i++)
    Just do the sqrt() once, not each time round every loop.

    > tPart = particles[10*i+j];
    Did you flatten the array because you don't know how to pass a 2D array to a function?

  3. #3
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    Thanks

    And.. hmm, don't know why I did like that ^^ Maybe because I wrote it in another way at first and it was easier to do like this then.

    Now I just discovered that my physics isn't as good as it's supposed to But that will soon be fixed.

    Thanks again

    The Wazaa

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