## Usage ```javascript var gcopy = require( '@stdlib/blas/base/gcopy' ); ``` #### gcopy( N, x, strideX, y, strideY ) Copies values from `x` into `y`. ```javascript var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ]; var y = [ 6.0, 7.0, 8.0, 9.0, 10.0 ]; gcopy( x.length, x, 1, y, 1 ); // y => [ 1.0, 2.0, 3.0, 4.0, 5.0 ] ``` The function has the following parameters: - **N**: number of indexed elements. - **x**: input array. - **strideX**: index increment for `x`. - **y**: output array. - **strideY**: index increment for `y`. The `N` and stride parameters determine how values from `x` are copied into `y`. For example, to copy in reverse order every other value in `x` into the first `N` elements of `y`, ```javascript var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ]; var y = [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ]; gcopy( 3, x, -2, y, 1 ); // y => [ 5.0, 3.0, 1.0, 10.0, 11.0, 12.0 ] ``` Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views. ```javascript var Float64Array = require( '@stdlib/array/float64' ); // Initial arrays... var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] ); var y0 = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] ); // Create offset views... var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element // Copy in reverse order every other value from `x1` into `y1`... gcopy( 3, x1, -2, y1, 1 ); // y0 => [ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ] ``` #### gcopy.ndarray( N, x, strideX, offsetX, y, strideY, offsetY ) Copies values from `x` into `y` using alternative indexing semantics. ```javascript var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ]; var y = [ 6.0, 7.0, 8.0, 9.0, 10.0 ]; gcopy.ndarray( x.length, x, 1, 0, y, 1, 0 ); // y => [ 1.0, 2.0, 3.0, 4.0, 5.0 ] ``` The function has the following additional parameters: - **offsetX**: starting index for `x`. - **offsetY**: starting index for `y`. While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to copy every other value in `x` starting from the second value into the last `N` elements in `y` where `x[i] = y[n]`, `x[i+2] = y[n-1]`,..., ```javascript var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ]; var y = [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ]; gcopy.ndarray( 3, x, 2, 1, y, -1, y.length-1 ); // y => [ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ] ```

## Notes - If `N <= 0`, both functions return `y` unchanged. - Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/complex64`][@stdlib/array/complex64]). - `gcopy()` corresponds to the [BLAS][blas] level 1 function [`dcopy`][dcopy] with the exception that this implementation works with any array type, not just Float64Arrays. Depending on the environment, the typed versions ([`dcopy`][@stdlib/blas/base/dcopy], [`scopy`][@stdlib/blas/base/scopy], etc.) are likely to be significantly more performant.