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139 lines (120 loc) · 3.49 KB
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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 isArrayLikeObject = require( '@stdlib/assert/is-array-like-object' );
var format = require( '@stdlib/string/format' );
// FUNCTIONS //
/**
* Recursively (and eagerly) attempts to resolve nested array dimensions.
*
* @private
* @param {Array} shape - output array
* @param {ArrayLikeObject} arr - array
* @returns {Array} shape array
*/
function recurse( shape, arr ) {
var v = arr[ 0 ];
if ( isArrayLikeObject( v ) ) {
shape.push( v.length );
recurse( shape, v );
}
return shape;
}
/**
* Recursively verifies that all nested arrays have consistent dimensions.
*
* @private
* @param {PositiveInteger} ndims - number of dimensions
* @param {Array} shape - shape array
* @param {NonNegativeInteger} d - dimension
* @param {ArrayLikeObject} arr - array element to verify
* @param {boolean} flg - boolean indicating whether to continue recursing
* @returns {NonNegativeInteger} number of consistent dimensions
*/
function check( ndims, shape, d, arr, flg ) {
var len;
var v;
var i;
// Get the size of the current dimension:
len = shape[ d ];
// Ensure that each array element is an array of the same size:
for ( i = 0; i < arr.length; i++ ) {
v = arr[ i ];
// If the array element is not an array or is not the same size, we have found an inconsistent dimension:
if ( !isArrayLikeObject( v ) || v.length !== len ) {
// `d` is one more than the index of the last consistent dimension and thus equal to the number of consistent dimensions:
return d;
}
// Recursively examine nested elements:
if ( flg ) {
v = check( ndims, shape, d+1, v, d+1 < ndims-1 );
if ( v < ndims ) {
// Propagate the number of consistent dimensions up the recursion chain...
return v;
}
}
}
return ndims;
}
// MAIN //
/**
* Determines (nested) array dimensions.
*
* @param {ArrayLikeObject} arr - array
* @throws {TypeError} must provide an array
* @returns {Array} array shape
*
* @example
* var arr = [ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ] ];
*
* var shape = arrayShape( arr );
* // returns [ 3, 3 ]
*
* @example
* var arr = [ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8 ] ];
*
* var shape = arrayShape( arr );
* // returns [ 3 ]
*
* @example
* var arr = [ [ 1, 2, 3 ], [ 4, 5, 6 ], null ];
*
* var shape = arrayShape( arr );
* // returns [ 3 ]
*/
function arrayShape( arr ) {
var shape;
var ndims;
if ( !isArrayLikeObject( arr ) ) {
throw new TypeError( format( 'invalid argument. Must provide an array-like object. Value: `%s`.', arr ) );
}
// Initialize the shape/dimensions array:
shape = [ arr.length ];
// Eagerly determine array dimensions:
recurse( shape, arr );
ndims = shape.length;
// Check that all array element dimensions are consistent:
if ( ndims > 1 ) {
// If `check()` returns a value less than `ndims`, trim off the inconsistent dimensions:
shape.length = check( ndims, shape, 1, arr, ndims > 2 );
}
return shape;
}
// EXPORTS //
module.exports = arrayShape;