Adding two arrays?

Question

In the Arduino IDE, I'd like to add the contents of two existing arrays like this:

#define L0 { {0, 0, 0, 0}, {0, 0, 0, 1}, {0, 0, 0, 0} }
#define L1 { {0, 0, 0, 1}, {0, 0, 0, 0}, {0, 0, 0, 0} }

should become

   int myarray[3][4] = { {0, 0, 0, 1}, {0, 0, 0, 1}, {0, 0, 0, 0} }

How would I go about this?

Thanks!

wrap the array in a class, initialise the content in the constructor, and create a function with a static instance variable of the class, return a reference to the wrapped array — lurscher
– lurscher, Commented Oct 12, 2012 at 19:21
@lurscher - The correct answer is clearly Array(L0)+Array(L1). How you implement the Array class is an exercise for the reader :). — slugonamission
– slugonamission, Commented Oct 12, 2012 at 19:52

Steztric · Accepted Answer · 2012-10-12 20:34:57Z

2

Thy this;

const int a[3][4] = { {0, 0, 0, 0}, {0, 0, 0, 1}, {0, 0, 0, 0} };
const int b[3][4] = { {0, 0, 0, 1}, {0, 0, 0, 0}, {0, 0, 0, 0} };

int c[3][4];

const int* pa = &a[0][0];
const int* pb = &b[0][0];
int* pc = &c[0][0];

for(int i = 0; i < 3 * 4; ++i)
{
    *(pc + i) = *(pa + i) + *(pb + i);
}

answered Oct 12, 2012 at 20:34

Steztric

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P.P · Accepted Answer · 2012-10-12 19:44:28Z

2

I think you are confused about how to go access the arrays L0 and L1 since they are defined as macros. Just assign them to arrays since the preprocessor will simply replace them:

int l[][4]=L0;
int m[][4]=L1;

Preprocessor will replace L0 and L1 with their values and compiler will only see them as:

int l[][4]={ {0, 0, 0, 0}, {0, 0, 0, 1}, {0, 2, 0, 0} };
int m[][4]={ {0, 0, 0, 5}, {0, 0, 0, 6}, {0, 0, 7, 0} };

Now, you can use l & m to access the elements of array. Should easy enough from here to add two arrays :)

answered Oct 12, 2012 at 19:44

P.P

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