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Create an iterator from a strided array-like object.
npm install @stdlib/array-to-strided-iteratorAlternatively,
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var stridedarray2iterator = require( '@stdlib/array-to-strided-iterator' );Returns an iterator which iterates over elements in an array-like object according to specified stride parameters.
var values = [ 1, 2, 3, 4, 5, 6, 7, 8 ];
var N = 4;
var stride = -2;
var offset = 6;
var it = stridedarray2iterator( N, values, stride, offset );
// returns <Object>
var v = it.next().value;
// returns 7
v = it.next().value;
// returns 5
v = it.next().value;
// returns 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
valueproperty and adoneproperty having abooleanvalue indicating whether the iterator is finished. - return: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.
To invoke a function for each src value, provide a callback function.
function fcn( v ) {
return v * 10.0;
}
var it = stridedarray2iterator( 4, [ 1, 2, 3, 4 ], 1, 0, fcn );
// returns <Object>
var v = it.next().value;
// returns 10.0
v = it.next().value;
// returns 20.0
v = it.next().value;
// returns 30.0
// ...The invoked function is provided four arguments:
- value: iterated value.
- index: iterated value index.
- n: iteration count (zero-based).
- src: source array-like object.
function fcn( v, i ) {
return v * (i+1);
}
var it = stridedarray2iterator( 4, [ 1, 2, 3, 4 ], 1, 0, fcn );
// returns <Object>
var v = it.next().value;
// returns 1
v = it.next().value;
// returns 4
v = it.next().value;
// returns 9
// ...To set the callback function execution context, provide a thisArg.
function fcn( v ) {
this.count += 1;
return v * 10.0;
}
var ctx = {
'count': 0
};
var it = stridedarray2iterator( 4, [ 1, 2, 3, 4 ], 1, 0, fcn, ctx );
// returns <Object>
var v = it.next().value;
// returns 10.0
v = it.next().value;
// returns 20.0
v = it.next().value;
// returns 30.0
var count = ctx.count;
// returns 3- If an environment supports
Symbol.iterator, the returned iterator is iterable. - If provided a generic
array, the returned iterator does not ignore holes. To achieve greater performance for sparse arrays, use a custom iterator. - A returned iterator does not copy a provided array-like
object. To ensure iterable reproducibility, copy a provided array-likeobjectbefore creating an iterator. Otherwise, any changes to the contents of an array-likeobjectwill be reflected in the returned iterator. - In environments supporting
Symbol.iterator, the function explicitly does not invoke an array's@@iteratormethod, regardless of whether this method is defined. To convert an array to an implementation defined iterator, invoke this method directly. - The returned iterator supports array-like objects having getter and setter accessors for array element access (e.g.,
@stdlib/array-complex64).
var Float64Array = require( '@stdlib/array-float64' );
var inmap = require( '@stdlib/utils-inmap' );
var randu = require( '@stdlib/random-base-randu' );
var stridedarray2iterator = require( '@stdlib/array-to-strided-iterator' );
function scale( v, i ) {
return v * (i+1);
}
// Create an array filled with random numbers:
var arr = inmap( new Float64Array( 100 ), randu );
// Create an iterator which scales every fourth value in reverse order:
var it = stridedarray2iterator( 25, arr, -4, 99, scale );
// Perform manual iteration...
var v;
while ( true ) {
v = it.next();
if ( v.done ) {
break;
}
console.log( v.value );
}@stdlib/array-from-iterator: create (or fill) an array from an iterator.@stdlib/array-to-iterator: create an iterator from an array-like object.
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See LICENSE.
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