append

Appends individual elements or another array, returning a new array. The first two overloads flatten both arrays to 1D before concatenating; the axis-based overload preserves dimensionality.

Signatures

// Append individual elements (flattens to 1D)
fun <T, D : Dimension> MultiArray<T, D>.append(vararg value: T): D1Array<T>

// Append another array (flattens to 1D)
infix fun <T, D : Dimension, ID : Dimension> MultiArray<T, D>.append(
    arr: MultiArray<T, ID>
): D1Array<T>

// Append along a specific axis (preserves dimensionality)
fun <T, D : Dimension> MultiArray<T, D>.append(
    arr: MultiArray<T, D>, axis: Int
): NDArray<T, D>

Parameters

Parameter	Type	Description
`value`	`vararg T`	Individual elements to append.
`arr`	`MultiArray<T, *>`	Array whose elements are appended.
`axis`	`Int`	Axis along which to concatenate (only for the shaped overload).

Returns:

Without axis: D1Array<T> — a new flat 1D array with the appended elements.
With axis: NDArray<T, D> — a new array concatenated along the given axis.

Example

val a = mk.ndarray(mk[1, 2, 3])

// Append individual elements
a.append(4, 5)               // [1, 2, 3, 4, 5]

// Append another array (flattened)
val b = mk.ndarray(mk[10, 20])
a append b                   // [1, 2, 3, 10, 20]

// Append along an axis
val m1 = mk.ndarray(mk[mk[1, 2], mk[3, 4]])
val m2 = mk.ndarray(mk[mk[5, 6]])
m1.append(m2, axis = 0)
// [[1, 2],
//  [3, 4],
//  [5, 6]]

28 February 2026