134 lines
2.5 KiB
JavaScript
134 lines
2.5 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 objectKeys = require( '@stdlib/utils/keys' );
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var hasOwnProp = require( '@stdlib/assert/has-own-property' );
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var SAFE_CASTS = require( './safe_casts.json' );
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// VARIABLES //
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var TABLE;
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// FUNCTIONS //
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/**
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* Generates a full table of safe casts for each array data type.
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*
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* @private
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* @returns {Object} table
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*/
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function generateFullTable() {
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var dtypes;
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var ntypes;
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var out;
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var tmp;
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var dt1;
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var dt2;
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var o;
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var j;
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var i;
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out = {};
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dtypes = objectKeys( SAFE_CASTS );
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ntypes = dtypes.length;
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for ( i = 0; i < ntypes; i++ ) {
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dt1 = dtypes[ i ];
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o = SAFE_CASTS[ dt1 ];
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tmp = {};
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for ( j = 0; j < ntypes; j++ ) {
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dt2 = dtypes[ j ];
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tmp[ dt2 ] = o[ dt2 ];
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}
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out[ dt1 ] = tmp;
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}
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return out;
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}
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/**
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* Generates a table of safe casts for each array data type.
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*
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* @private
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* @returns {Object} table
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*/
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function generateTable() {
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var dtypes;
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var ntypes;
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var out;
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var tmp;
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var dt1;
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var dt2;
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var o;
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var j;
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var i;
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out = {};
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dtypes = objectKeys( SAFE_CASTS );
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ntypes = dtypes.length;
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for ( i = 0; i < ntypes; i++ ) {
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dt1 = dtypes[ i ];
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o = SAFE_CASTS[ dt1 ];
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tmp = [];
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for ( j = 0; j < ntypes; j++ ) {
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dt2 = dtypes[ j ];
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if ( o[ dt2 ] === 1 ) {
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tmp.push( dt2 );
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}
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}
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out[ dt1 ] = tmp;
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}
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return out;
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}
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// MAIN //
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/**
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* Returns a list of array data types to which a provided array data type can be safely cast.
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*
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* @param {string} [dtype] - array data type
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* @returns {(Object|StringArray|null)} list of array data types or null
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*
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* @example
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* var list = safeCasts( 'float32' );
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* // returns [...]
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*/
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function safeCasts( dtype ) {
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if ( arguments.length === 0 ) {
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return generateFullTable();
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}
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if ( TABLE === void 0 ) {
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// Lazily generate table...
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TABLE = generateTable();
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}
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if ( hasOwnProp( TABLE, dtype ) ) {
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return TABLE[ dtype ].slice();
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}
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return null;
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}
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// EXPORTS //
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module.exports = safeCasts;
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