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Programming-Idioms

  • Scala
  • Pascal
  • C++

Idiom #309 Clone a 2D array

Create the new 2-dimensional array y containing a copy of the elements of the 2-dimensional array x.

x and y must not share memory. Subsequent modifications of y must not affect x.

func clone2D[M ~[][]T, T any](in M) (out M) {
	if len(in) == 0 {
		return nil
	}

	m, n := len(in), len(in[0])

	buf := make([]T, m*n)

	out = make(M, m)
	for i := range out {
		out[i] = buf[:n:n]
		buf = buf[n:]
		copy(out[i], in[i])
	}
	return out
}

Allocate a large buffer, slice it, copy the data.
buf := make([]T, m*n)
y = make([][]T, m)
for i := range y {
	y[i] = buf[:n:n]
	buf = buf[n:]
	copy(y[i], x[i])
}

Allocate a large buffer, slice it, copy the data.
y := x;

For static arrays only
y := copy(x, Low(x), Length(x));

For dynamic arrays
integer, allocatable, dimension(:,:) :: y

y = x

An allocatable array takes the bounds of thr right hand side upon assignment.
New implementation...
< > ⌨
programming-idioms.org 
func clone2D[M ~[][]T, T any](in M) (out M) {
	if len(in) == 0 {
		return nil
	}

	m, n := len(in), len(in[0])

	buf := make([]T, m*n)

	out = make(M, m)
	for i := range out {
		out[i] = buf[:n:n]
		buf = buf[n:]
		copy(out[i], in[i])
	}
	return out
}
buf := make([]T, m*n)
y = make([][]T, m)
for i := range y {
	y[i] = buf[:n:n]
	buf = buf[n:]
	copy(y[i], x[i])
}
y := x;
y := copy(x, Low(x), Length(x));
integer, allocatable, dimension(:,:) :: y

y = x
Class<?> c = x.getClass(),
         a = c.getComponentType(),
         b = a.getComponentType();
int i, m = x.length, n;
T y[][] = (T[][]) newInstance(a, m), Y[], t[];
for (i = 0; i < m; ++i) {
    n = (t = x[i]).length;
    Y = (T[]) newInstance(b, n);
    arraycopy(t, 0, Y, 0, n);
    y[i] = Y;
}
int i, m = x.length, n,
    y[][] = new int[m][], Y[], t[];
for (i = 0; i < m; ++i) {
    n = (t = x[i]).length;
    Y = new int[n];
    arraycopy(t, 0, Y, 0, n);
    y[i] = Y;
}
int i, m = x.length, n,
    y[][] = new int[m][], t[];
for (i = 0; i < m; ++i) {
    n = (t = x[i]).length;
    y[i] = copyOf(t, n);
}
$y = dclone($x);
y = copy.deepcopy(x)
y = Marshal.load(Marshal.dump(x))
let y = x.clone();