107 lines
2.8 KiB
JavaScript
107 lines
2.8 KiB
JavaScript
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var isInteger = require( '@stdlib/assert/is-integer' );
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var isArray = require( '@stdlib/assert/is-array' );
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// MAIN //
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/**
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* Unzips a zipped array (i.e., a nested array of tuples).
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*
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* @param {Array} arr - zipped array
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* @param {Array} [idx] - array of indices specifying which tuple elements to unzip
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* @throws {TypeError} first argument must be a zipped array
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* @throws {TypeError} second argument must be an array of integer indices
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* @throws {Error} indices must be on the interval from zero to the tuple length
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* @returns {Array} array of unzipped arrays
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*
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* @example
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* var arr = [ [ 1, 'a', 3 ], [ 2, 'b', 4 ] ];
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*
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* var out = unzip( arr );
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* // returns [ [ 1, 2 ], [ 'a', 'b' ], [ 3, 4 ] ]
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*
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* @example
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* var arr = [ [ 1, 'a', 3 ], [ 2, 'b', 4 ] ];
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*
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* var out = unzip( arr, [ 0, 2 ] );
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* // returns [ [ 1, 2 ], [ 3, 4 ] ]
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*/
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function unzip( arr, idx ) {
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var numVals;
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var len;
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var out;
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var tmp;
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var i;
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var j;
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var k;
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if ( !isArray( arr ) ) {
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throw new TypeError( 'invalid argument. Must provide a zipped array.' );
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}
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len = arr.length;
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for ( i = 0; i < len; i++ ) {
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if ( !isArray( arr[i] ) ) {
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throw new TypeError( 'invalid argument. Array must only contain arrays.' );
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}
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}
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// Assume that the first tuple is representative of all tuples...
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numVals = arr[ 0 ].length;
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if ( arguments.length > 1 ) {
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if ( !isArray( idx ) ) {
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throw new TypeError( 'invalid argument. Indices must be specified as an array.' );
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}
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for ( i = 0; i < idx.length; i++ ) {
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k = idx[ i ];
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if ( !isInteger( k ) ) {
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throw new TypeError( 'invalid argument. All indices must be integers.' );
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}
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if ( k < 0 || k > numVals ) {
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throw new Error( 'invalid argument. Must provide valid indices; i.e., an index must be on the interval [0,len], where len is the tuple length.' );
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}
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}
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numVals = idx.length;
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} else {
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idx = new Array( numVals );
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for ( i = 0; i < numVals; i++ ) {
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idx[ i ] = i;
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}
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}
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out = new Array( numVals );
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for ( j = 0; j < numVals; j++ ) {
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tmp = new Array( len );
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k = idx[ j ];
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for ( i = 0; i < len; i++ ) {
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tmp[ i ] = arr[ i ][ k ];
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}
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out[ j ] = tmp;
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}
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return out;
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}
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// EXPORTS //
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module.exports = unzip;
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