nditerEntries

Create an iterator which returns [index, value] pairs for each element in a provided ndarray.

Usage

var nditerEntries = require( '@stdlib/ndarray/iter/entries' );

nditerEntries( x[, options] )

Returns an iterator which returns [index, value] pairs for each element in a provided ndarray.

var array = require( '@stdlib/ndarray/array' );

var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ] );
// returns <ndarray>

var iter = nditerEntries( x );

var v = iter.next().value;
// returns [ [ 0, 0, 0 ], 1 ]

v = iter.next().value;
// returns [ [ 0, 0, 1 ], 2 ]

v = iter.next().value;
// returns [ [ 0, 1, 0 ], 3 ]

// ...

The function accepts the following options:

  • order: index iteration order. By default, the returned iterator returns values according to the layout order of the provided array. Accordingly, for row-major input arrays, the last dimension indices increment fastest. For column-major input arrays, the first dimension indices increment fastest. To override the inferred order and ensure that indices increment in a specific manor, regardless of the input array's layout order, explicitly set the iteration order. Note, however, that iterating according to an order which does not match that of the input array may, in some circumstances, result in performance degradation due to cache misses. Must be either 'row-major' or 'column-major'.

By default, the iterator iterates according to the layout order of the input ndarray. To iterate according to a specified order, set the order option.

var array = require( '@stdlib/ndarray/array' );

var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ], {
    'order': 'row-major'
});
// returns <ndarray>

var iter = nditerEntries( x, {
    'order': 'column-major'
});

var v = iter.next().value;
// returns [ [ 0, 0, 0 ], 1 ]

v = iter.next().value;
// returns [ [ 1, 0, 0 ], 5 ]

v = iter.next().value;
// returns [ [ 0, 1, 0 ], 3 ]

// ...

The returned iterator protocol-compliant object has the following properties:

  • next: function which returns an iterator protocol-compliant object containing the next iterated value (if one exists) assigned to a value property and a done property having a boolean value indicating whether the iterator is finished.
  • return: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.

Notes

  • Each returned index is a Cartesian index (i.e., an array of subscripts/dimension indices).
  • If an environment supports Symbol.iterator, the returned iterator is iterable.
  • A returned iterator does not copy a provided ndarray. To ensure iterable reproducibility, copy the input ndarray before creating an iterator. Otherwise, any changes to the contents of input ndarray will be reflected in the returned iterator.
  • In environments supporting Symbol.iterator, the function explicitly does not invoke an ndarray's @@iterator method, regardless of whether this method is defined.

Examples

var array = require( '@stdlib/ndarray/array' );
var zeroTo = require( '@stdlib/array/base/zero-to' );
var nditerEntries = require( '@stdlib/ndarray/iter/entries' );

// Define an input array:
var x = array( zeroTo( 27 ), {
    'shape': [ 3, 3, 3 ]
});

// Create an iterator for returning [index, value] pairs:
var it = nditerEntries( x );

// Perform manual iteration...
var v;
while ( true ) {
    v = it.next();
    if ( v.done ) {
        break;
    }
    console.log( v.value );
}

See Also

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