Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 | 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x | /**
* @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 first element (or subarray) along one or more ndarray dimensions.
*
* ## Notes
*
* - By default, the function performs the operation over all dimensions and thus returns the first 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 = first( x );
* // returns <ndarray>[ 1.0 ]
*
* v = first( x, {
* 'dims': [ -1 ]
* });
* // returns <ndarray>[ 1.0, 3.0 ]
*
* v = first( x, {
* 'dims': [ -2 ]
* });
* // returns <ndarray>[ 1.0, 2.0 ]
*/
function first( 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 first index and all other dimensions are kept in full:
args = nulls( N );
for ( i = 0; i < dims.length; i++ ) {
args[ dims[ i ] ] = 0;
}
return base( x, args2multislice( args ), true, false );
}
// EXPORTS //
module.exports = first;
|