66 lines
1.4 KiB
JavaScript
66 lines
1.4 KiB
JavaScript
/**
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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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// MAIN //
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/**
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* Wraps an index on the interval `[0,max]`.
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*
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* @param {integer} idx - index
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* @param {NonNegativeInteger} max - maximum index
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* @returns {NonNegativeInteger} index
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*
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* @example
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* var idx = wrapIndex( -1, 10 );
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* // returns 10
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*
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* idx = wrapIndex( 13, 10 );
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* // returns 2
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*
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* idx = wrapIndex( 6, 10 );
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* // returns 6
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*/
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function wrapIndex( idx, max ) {
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var mp1 = max + 1;
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if ( idx < 0 ) {
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idx += mp1; // slight optimization to avoid modulo arithmetic when |idx| <= max+1
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if ( idx < 0 ) {
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idx %= mp1;
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if ( idx !== 0 ) {
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idx += mp1;
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}
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}
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return idx;
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}
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if ( idx > max ) {
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idx -= mp1; // slight optimization to avoid modulo arithmetic when max+1 < idx <= 2*(max+1)
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if ( idx > max ) {
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idx %= mp1;
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}
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return idx;
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}
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return idx;
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}
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// EXPORTS //
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module.exports = wrapIndex;
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