{{alias}}( N, order, x, stride )
    Sorts a double-precision floating-point strided array using heapsort.

    The `N` and `stride` parameters determine which elements in `x` are accessed
    at runtime.

    Indexing is relative to the first index. To introduce an offset, use typed
    array views.

    If `N <= 0` or `order == 0`, the function returns `x` unchanged.

    The algorithm distinguishes between `-0` and `+0`. When sorted in increasing
    order, `-0` is sorted before `+0`. When sorted in decreasing order, `-0` is
    sorted after `+0`.

    The algorithm sorts `NaN` values to the end. When sorted in increasing
    order, `NaN` values are sorted last. When sorted in decreasing order, `NaN`
    values are sorted first.

    The algorithm has space complexity O(1) and time complexity O(N log2 N).

    The algorithm is *unstable*, meaning that the algorithm may change the order
    of strided array elements which are equal or equivalent (e.g., `NaN`
    values).

    The input strided array is sorted *in-place* (i.e., the input strided array
    is *mutated*).

    Parameters
    ----------
    N: integer
        Number of indexed elements.

    order: number
        Sort order. If `order < 0`, the function sorts `x` in decreasing order.
        If `order > 0`, the function sorts `x` in increasing order.

    x: Float64Array
        Input array.

    stride: integer
        Index increment for `x`.

    Returns
    -------
    x: Float64Array
        Input array `x`.

    Examples
    --------
    // Standard Usage:
    > var x = new {{alias:@stdlib/array/float64}}( [ 1.0, -2.0, 3.0, -4.0 ] );
    > {{alias}}( x.length, 1, x, 1 )
    <Float64Array>[ -4.0, -2.0, 1.0, 3.0 ]

    // Using `N` and `stride` parameters:
    > x = new {{alias:@stdlib/array/float64}}( [ 1.0, -2.0, 3.0, -4.0 ] );
    > var N = {{alias:@stdlib/math/base/special/floor}}( x.length / 2 );
    > {{alias}}( N, -1, x, 2 )
    <Float64Array>[ 3.0, -2.0, 1.0, -4.0 ]

    // Using view offsets:
    > var x0 = new {{alias:@stdlib/array/float64}}( [ 1.0, -2.0, 3.0, -4.0 ] );
    > var x1 = new {{alias:@stdlib/array/float64}}( x0.buffer, x0.BYTES_PER_ELEMENT*1 );
    > N = {{alias:@stdlib/math/base/special/floor}}( x0.length / 2 );
    > {{alias}}( N, 1, x1, 2 )
    <Float64Array>[ -4.0, 3.0, -2.0 ]
    > x0
    <Float64Array>[ 1.0, -4.0, 3.0, -2.0 ]

{{alias}}.ndarray( N, order, x, stride, offset )
    Sorts a double-precision floating-point strided array using heapsort and
    alternative indexing semantics.

    While typed array views mandate a view offset based on the underlying
    buffer, the `offset` parameter supports indexing semantics based on a
    starting index.

    Parameters
    ----------
    N: integer
        Number of indexed elements.

    order: number
        Sort order. If `order < 0`, the function sorts `x` in decreasing order.
        If `order > 0`, the function sorts `x` in increasing order.

    x: Float64Array
        Input array.

    stride: integer
        Index increment for `x`.

    offset: integer
        Starting index of `x`.

    Returns
    -------
    x: Float64Array
        Input array `x`.

    Examples
    --------
    // Standard Usage:
    > var x = new {{alias:@stdlib/array/float64}}( [ 1.0, -2.0, 3.0, -4.0 ] );
    > {{alias}}.ndarray( x.length, 1, x, 1, 0 )
    <Float64Array>[ -4.0, -2.0, 1.0, 3.0 ]

    // Using an index offset:
    > x = new {{alias:@stdlib/array/float64}}( [ 1.0, -2.0, 3.0, -4.0 ] );
    > var N = {{alias:@stdlib/math/base/special/floor}}( x.length / 2 );
    > {{alias}}.ndarray( N, 1, x, 2, 1 )
    <Float64Array>[ 1.0, -4.0, 3.0, -2.0 ]

    See Also
    --------