time-to-botec

README.md (6013B)

---

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 # Strided Iterator
 
 > Create an [iterator][mdn-iterator-protocol] from a strided array-like object.
 
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 <section class="intro">
 
 </section>
 
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 <!-- Package usage documentation. -->
 
 <section class="usage">
 
 ## Usage
 
 ```javascript
 var stridedarray2iterator = require( '@stdlib/array/to-strided-iterator' );
 ```
 
 #### stridedarray2iterator( N, src, stride, offset\[, mapFcn\[, thisArg]] )
 
 Returns an [iterator][mdn-iterator-protocol] which iterates over elements in an array-like `object` according to specified stride parameters.
 
 ```javascript
 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][mdn-iterator-protocol] protocol-compliant object has the following properties:
 
 -   **next**: function which returns an [iterator][mdn-iterator-protocol] 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][mdn-iterator-protocol] is finished.
 -   **return**: function which closes an [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an iterator protocol-compliant object.
 
 To invoke a function for each `src` value, provide a callback function.
 
 ```javascript
 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
 
 ```javascript
 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`.
 
 ```javascript
 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
 ```
 
 </section>
 
 <!-- /.usage -->
 
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 <section class="notes">
 
 ## Notes
 
 -   If an environment supports `Symbol.iterator`, the returned [iterator][mdn-iterator-protocol] is iterable.
 -   If provided a generic `array`, the returned [iterator][mdn-iterator-protocol] does **not** ignore holes. To achieve greater performance for sparse arrays, use a custom [iterator][mdn-iterator-protocol].
 -   A returned [iterator][mdn-iterator-protocol] does **not** copy a provided array-like `object`. To ensure iterable reproducibility, copy a provided array-like `object` **before** creating an [iterator][mdn-iterator-protocol]. Otherwise, any changes to the contents of an array-like `object` will be reflected in the returned [iterator][mdn-iterator-protocol].
 -   In environments supporting `Symbol.iterator`, the function **explicitly** does **not** invoke an array's `@@iterator` method, regardless of whether this method is defined. To convert an array to an implementation defined [iterator][mdn-iterator-protocol], invoke this method directly.
 
 </section>
 
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 <section class="examples">
 
 ## Examples
 
 <!-- eslint no-undef: "error" -->
 
 ```javascript
 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 );
 }
 ```
 
 </section>
 
 <!-- /.examples -->
 
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 </section>
 
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 <section class="links">
 
 [mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol
 
 </section>
 
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