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Index › Programming Questions & Help › Syntax Questions › expand()ing multi-dimensional arrays
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expand()ing multi-dimensional arrays (Read 1298 times)
Lone_Pairs
expand()ing multi-dimensional arrays
Apr 5th, 2007, 4:42am  
I've been trying to figure out how to expand two- and three- dimensional arrays, but I've been unable to figure out how to do certain things.

here is my test code:

int[][] two=new int[1][3];
int x, y;
void setup(){
 size(400,400);
 colorMode(RGB,100);
 noStroke();
 for(x=0;x<two.length;x++){
 for(y=0;y<two[x].length;y++){
   fill(two[x][y]);
   rect(x*5,y*5,5,5);
 }
 }
}
void draw(){}

void mouseClicked(){
 two[0]=(int[])expand(two[0]);
 
 for(x=0;x<two.length;x++){
 for(y=0;y<two[x].length;y++){
   two[x][y]=(int)random(40);
 }
 }
 for(x=0;x<two.length;x++){
 for(y=0;y<two[x].length;y++){
   fill(two[x][y]);
   rect(x*5,y*5,5,5);
 }
 }
}


this statement expands the second array,
two[0]=(int[])expand(two[0]);
But only for two[0], how would I go about expanding two[0...n] all at once?

Also, when I try to expand the first array ( two=(int[][])expand(two); )I get a null pointer exception at
"for(y=0;y<two[x].length;y++){" and if I switch the "two[x]" to "two[0]" the error just shifts down a line.

what am I doing wrong?

Lastly, and sort of unrelated, if I have an array of some type of object, and want to shrink it, how do I?  the processing reference says that contract has been removed, and that I should use subset instead, but subset says it only works on base arrays, as does shorten, what do I do?

preemptive thanks.
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fjen
Re: expand()ing multi-dimensional arrays
Reply #1 - Apr 5th, 2007, 12:36pm  
Code:


int[][] two=new int[1][3]; 
int x, y; 
void setup(){ 
    size(400,400); 
    colorMode(RGB,100); 
    noStroke(); 
    for(x=0;x<two.length;x++){ 
	  for(y=0;y<two[x].length;y++){ 
		fill(two[x][y]); 
		rect(x*5,y*5,5,5); 
	  } 
    } 
} 
void draw(){
} 

void mouseClicked(){ 

    // set this to "true" for other example
    if ( false ) {
	  // since you don't use the old values anyway
	  two = new int[two.length+1][3];

	  for(x=0;x<two.length;x++){ 
		for(y=0;y<two[x].length;y++){
		    two[x][y]=(int)random(40); 
		} 
	  }
    }  
    else {

	  // if you would like to keep the old values do:
	  int[][] tmp = new int[1][3];

	  for(x=0;x<tmp.length;x++){ 
		for(y=0;y<tmp[x].length;y++){
		    tmp[x][y]=(int)random(40); 
		} 
	  }
	  two = (int[][])concat( two, tmp );
    } 

    for(x=0;x<two.length;x++){ 
	  for(y=0;y<two[x].length;y++){ 
		fill(two[x][y]); 
		rect(x*5,y*5,5,5); 
	  } 
    } 
}


and

Code:


void setup ()
{
    Foo sa1[] = { 
	  new Foo(), new Foo(), new Foo(), new Foo(), new Foo(), new Foo(), new Foo() };
    Foo sa2[] = (Foo[])subset(sa1, 1);
    print(sa2);  // Prints "NY CA VA CO IL "
    println();
    Foo sa3[] = (Foo[])subset(sa1, 2, 3);
    print(sa3);  // Prints "CA VA CO "
}

int fooCount = 0;
class Foo
{
    int fooId;
    Foo ()
    {
	  fooId = ++fooCount;
    }
    public String toString ()
    {
	  return "Foo: "+fooId+"\n";
    }
}


F
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Lone_Pairs
Re: expand()ing multi-dimensional arrays
Reply #2 - Apr 5th, 2007, 9:54pm  
Thanks, but isn't there a better way of expanding the array and keeping the data?  That'll slow down the program once I'm using bigger arrays (as in [100][983040]) and have to load in 99 temp[]s.

Edit:
wait, nevermind. that works fine.
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