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* @license Apache-2.0
*
* Copyright (c) 2026 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var isndarrayLike = require( '@stdlib/assert/is-ndarray-like' );
var args2multislice = require( '@stdlib/slice/base/args2multislice' );
var base = require( '@stdlib/ndarray/base/slice' );
var getShape = require( '@stdlib/ndarray/shape' );
var zeroTo = require( '@stdlib/array/base/zero-to' );
var nulls = require( '@stdlib/array/base/nulls' );
var objectAssign = require( '@stdlib/object/assign' );
var format = require( '@stdlib/string/format' );
var defaults = require( './defaults.json' );
var validate = require( './validate.js' );
// MAIN //
/**
* Returns a read-only view of the last element (or subarray) along one or more ndarray dimensions.
*
* ## Notes
*
* - By default, the function performs the operation over all dimensions and thus returns the last element of the input ndarray as a zero-dimensional ndarray.
* - If provided an empty `dims` array, the function returns a read-only view of the input ndarray.
*
* @param {ndarray} x - input ndarray
* @param {Options} [options] - function options
* @param {IntegerArray} [options.dims] - list of dimensions over which to perform the operation
* @throws {TypeError} first argument must be an ndarray-like object
* @throws {TypeError} options argument must be an object
* @throws {TypeError} `dims` option must be an array of integers
* @throws {RangeError} `dims` option contains an out-of-bounds dimension index
* @throws {Error} `dims` option contains duplicate indices
* @returns {ndarray} ndarray view
*
* @example
* var array = require( '@stdlib/ndarray/array' );
*
* var x = array( [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] );
* // returns <ndarray>[ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ]
*
* var v = last( x );
* // returns <ndarray>[ 4.0 ]
*
* v = last( x, {
* 'dims': [ -1 ]
* });
* // returns <ndarray>[ 2.0, 4.0 ]
*
* v = last( x, {
* 'dims': [ -2 ]
* });
* // returns <ndarray>[ 3.0, 4.0 ]
*/
function last( x, options ) {
var args;
var opts;
var dims;
var err;
var sh;
var N;
var i;
if ( !isndarrayLike( x ) ) {
throw new TypeError( format( 'invalid argument. First argument must be an ndarray-like object. Value: `%s`.', x ) );
}
sh = getShape( x );
N = sh.length;
// Resolve options:
opts = objectAssign( {}, defaults );
if ( arguments.length > 1 ) {
err = validate( opts, N, options );
if ( err ) {
throw err;
}
}
if ( N === 0 ) {
return base( x, args2multislice( [] ), true, false );
}
if ( opts.dims === null ) {
dims = zeroTo( N );
} else {
dims = opts.dims;
}
// Build a list of slice arguments such that each dimension in `dims` resolves to its last index and all other dimensions are kept in full:
args = nulls( N );
for ( i = 0; i < dims.length; i++ ) {
args[ dims[ i ] ] = sh[ dims[ i ] ] - 1;
}
return base( x, args2multislice( args ), true, false );
}
// EXPORTS //
module.exports = last;
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