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* @license Apache-2.0
*
* Copyright (c) 2018 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 setReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
var isArrayLike = require( '@stdlib/assert/is-array-like' );
var isTypedArrayLike = require( '@stdlib/assert/is-typed-array-like' );
var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
var deepCopy = require( '@stdlib/utils/copy' );
var floor = require( '@stdlib/math/base/special/floor' );
var randu = require( '@stdlib/random/base/mt19937' ).factory;
var format = require( '@stdlib/string/format' );
var hasOwnProp = require( '@stdlib/assert/has-own-property' );
var defaults = require( './defaults.json' );
var validate = require( './validate.js' );
// MAIN //
/**
* Returns a function to create a random permutation of elements from an array-like object.
*
* @param {Options} [config] - function options
* @param {PositiveInteger} [config.seed] - integer-valued seed
* @param {string} [config.copy="shallow"] - default copy option (`deep`, `shallow` or `none`)
* @throws {TypeError} options argument must be an object
* @returns {Function} shuffle function
*
* @example
* var shuffle = factory({
* 'seed': 249
* });
* var data = [ 3, 8, 4, 8 ];
* var out = shuffle( data );
* // e.g., returns [ 4, 3, 8, 8 ]
*/
function factory( config ) {
var conf;
var rand;
var err;
conf = deepCopy( defaults );
if ( arguments.length ) {
err = validate( conf, config );
if ( err ) {
throw err;
}
}
if ( config && hasOwnProp( config, 'seed' ) ) {
rand = randu({
'seed': config.seed
});
} else {
rand = randu();
}
setReadOnly( shuffle, 'seed', rand.seed );
setReadOnly( shuffle, 'PRNG', rand );
rand = rand.normalized;
return shuffle;
/**
* Returns a random permutation of elements in `arr`.
*
* @private
* @param {(ArrayLike|TypedArrayLike)} arr - array-like object to shuffle
* @param {Options} [options] - function options
* @param {string} [options.copy] - string indicating whether to return a copy (`deep`,`shallow` or `none`)
* @throws {TypeError} first argument must be array-like
* @throws {TypeError} options must be an object
* @throws {TypeError} must provide valid options
* @returns {ArrayLike} the shuffled array-like object
*
* @example
* var data = [ 1, 2, 3 ];
* var out = shuffle( data );
* // e.g., returns [ 3, 1, 2 ]
*
* @example
* var data = [ 1, 2, 3 ];
* var out = shuffle( data, {
* 'copy': 'none'
* });
* var bool = ( data === out );
* // returns true
*/
function shuffle( arr, options ) {
var strflg;
var level;
var copy;
var opts;
var err;
var out;
var tmp;
var N;
var i;
var j;
if ( !( isArrayLike( arr ) || isTypedArrayLike( arr ) ) ) {
throw new TypeError( format( 'invalid argument. First argument must be array-like. Value: `%s`.', arr ) );
}
if ( arguments.length > 1 ) {
opts = {};
err = validate( opts, options );
if ( err ) {
throw err;
}
}
copy = ( opts && opts.copy ) ? opts.copy : conf.copy;
strflg = isString( arr );
if ( strflg ) {
arr = arr.split( '' );
copy = 'none';
}
level = 0;
if ( copy === 'shallow' ) {
level += 1;
} else if ( copy === 'deep' ) {
level += 2;
}
N = arr.length;
out = deepCopy( arr, level );
// Note: we skip the first element, as no further swaps are possible given that all other indices are excluded from swapping...
for ( i = N - 1; i > 0; i-- ) {
// Generate an integer index on the interval [0,i]:
j = floor( rand() * (i+1.0) );
// Swap elements:
tmp = out[ i ];
out[ i ] = out[ j ];
out[ j ] = tmp;
}
if ( strflg ) {
out = arr.join( '' );
}
return out;
}
}
// EXPORTS //
module.exports = factory;
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