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/**
* @license Apache-2.0
*
* Copyright (c) 2019 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';
// VARIABLES //
var TYPE_SORT_ORDER = {
'number': 0,
'string': 1,
'symbol': 2
};
// MAIN //
/**
* Returns the set difference between two similarly **sorted** lists.
*
* ## Notes
*
* - The contents of the provided arrays are assumed to be either numbers, strings, or symbols.
*
* - The lists are **expected** to be sorted not only, e.g., lexicographically, but also according to type in the **following** order: `numbers`, `strings`, and then `symbols`.
*
* ```text
* A = [ 1, 2, 3, '1', '2', '3', Symbol('1'), Symbol('2'), Symbol('3') ]
* B = [ 1, 2, '1', '3', Symbol('2'), Symbol('3') ]
* // => [ 3, '2', Symbol('1') ]
* ```
*
* @private
* @param {Array} A - first sorted list
* @param {Array} B - second sorted list
* @returns {Array} set difference
*
* @example
* var out = setdiff( [ 1, 2, 3 ], [ 2, 4, 5 ] );
* // returns [ 1, 3, 4, 5 ]
*
* @example
* var out = setdiff( [ 1 ], [ 2, 4, 5 ] );
* // returns [ 1, 2, 4, 5 ]
*
* @example
* var out = setdiff( [ 1, 2, 3 ], [ 2 ] );
* // returns [ 1, 3 ]
*
* @example
* var out = setdiff( [ 1, 2, 3 ], [] );
* // returns [ 1, 2, 3 ]
*
* @example
* var out = setdiff( [], [ 2, 4, 5 ] );
* // returns [ 2, 4, 5 ]
*
* @example
* var out = setdiff( [ 1, 2, 3 ], [ 1, 2, 3 ] );
* // returns []
*
* @example
* var out = setdiff( [], [] );
* // returns []
*
* @example
* var out = setdiff( [ 1 ], [ 1 ] );
* // returns []
*
* @example
* var out = setdiff( [ 1, 2, 2, 3, 3 ], [ 2, 4, 5, 5 ] );
* // returns [ 1, 2, 3, 3, 4, 5, 5 ]
*
* @example
* var out = setdiff( [ 1, 2, 3 ], [ 4, 5 ] );
* // returns [ 1, 2, 3, 4, 5 ]
*
* @example
* var out = setdiff( [ 1, 2 ], [ 3, 4, 5 ] );
* // returns [ 1, 2, 3, 4, 5 ]
*
* @example
* var out = setdiff( [ 1, 2, 3, 7 ], [ 0, 1, 2, 4, 5 ] );
* // returns [ 0, 3, 4, 5, 7 ]
*
* @example
* var out = setdiff( [ 1, 2, 3, 7, 9 ], [ -2, -1, 0, 1, 2, 4, 5 ] );
* // returns [ -2, -1, 0, 3, 4, 5, 7, 9 ]
*/
function setdiff( A, B ) {
var out;
var la;
var lb;
var ta;
var tb;
var a;
var b;
var i;
var j;
var k;
la = A.length;
lb = B.length;
if ( la === 0 ) {
return B.slice();
}
if ( lb === 0 ) {
return A.slice();
}
out = [];
i = 0;
j = 0;
while ( i < la && j < lb ) {
a = A[ i ];
b = B[ j ];
if ( a === b ) { // addresses numbers, strings, and symbols alike
i += 1;
j += 1;
continue;
}
ta = typeof a;
tb = typeof b;
if ( ta !== tb ) {
// Note: we assume we have found a "type" border!
ta = TYPE_SORT_ORDER[ ta ];
tb = TYPE_SORT_ORDER[ tb ];
if ( ta < tb ) {
out.push( a );
i += 1;
} else { // tb < ta
out.push( b );
j += 1;
}
}
// Note: the types for `a` and `b` are the *same*!
else if ( ta === 'symbol' ) {
// Note: symbols don't have a "natural" sort order, so we need to do things in a more computationally intensive way via linear scans...
while ( i < la ) {
for ( k = j+1; k < lb; k++ ) { // `j+1` because we already know the symbols are not equal
if ( a === B[ k ] ) {
break;
}
}
// If we searched through all the symbols in `B` and failed to find a match, we found a unique symbol...
if ( k === lb ) {
out.push( a );
} else {
// We can leverage the fact that symbols in `A` and `B` should be similarly sorted by recognizing that, if we found a match, this means that the symbols in `B` preceding the match should be unique...
for ( ; j < k; j++ ) {
out.push( B[ j ] );
}
}
i += 1;
}
} else if ( a < b ) {
out.push( a );
i += 1;
} else { // b < a
out.push( b );
j += 1;
}
}
if ( i < la ) {
for ( ; i < la; i++ ) {
out.push( A[ i ] );
}
}
if ( j < lb ) {
for ( ; j < lb; j++ ) {
out.push( B[ j ] );
}
}
return out;
}
// EXPORTS //
module.exports = setdiff;
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