Usage

`javascript
var map2 = require( '@stdlib/utils-map2' );
`

#### map2( x, y, fcn\[, thisArg] )

Applies a function to elements in two input arrays and assigns the results to a new array.

`javascript
var naryFunction = require( '@stdlib/utils-nary-function' );
var add = require( '@stdlib/number-float64-base-add' );

var x = [ 1, 2, 3, 4, 5, 6 ];
var y = [ 1, 1, 1, 1, 1, 1 ];

var out = map2( x, y, naryFunction( add, 2 ) );
// returns [ 2, 3, 4, 5, 6, 7 ]
`

The function accepts both array-like objects and [ndarray][@stdlib/ndarray/ctor]-like objects.

`javascript
var naryFunction = require( '@stdlib/utils-nary-function' );
var add = require( '@stdlib/number-float64-base-add' );
var array = require( '@stdlib/ndarray-array' );

var opts = {
'dtype': 'generic'
};
var x = array( [ [ 1, 2, 3 ], [ 4, 5, 6 ] ], opts );
var y = array( [ [ 1, 1, 1 ], [ 1, 1, 1 ] ], opts );

var out = map2( x, y, naryFunction( add, 2 ) );
// returns

var v = out.get( 1, 1 );
// returns 6
`

The applied function is provided the following arguments:

- v1: element from first input array.
- v2: element from second input array.
- idx: element index.
- arrays: input arrays.

To set the this context when invoking the input function, provide a thisArg.

`javascript
var add = require( '@stdlib/number-float64-base-add' );

function fcn( v1, v2 ) {
this.count += 1;
return add( v1, v2 );
}

var x = [ 1, 2, 3, 4, 5, 6 ];
var y = [ 1, 1, 1, 1, 1, 1 ];

var ctx = {
'count': 0
};

var out = map2( x, y, fcn, ctx );
// returns [ 2, 3, 4, 5, 6, 7 ]

var cnt = ctx.count;
// returns 6
`

#### map2.assign( x, y, out, fcn\[, thisArg] )

Applies a function to elements in two input arrays and assigns the results to an output array out.

`javascript
var naryFunction = require( '@stdlib/utils-nary-function' );
var add = require( '@stdlib/number-float64-base-add' );

var x = [ 1, 2, 3, 4, 5, 6 ];
var y = [ 1, 1, 1, 1, 1, 1 ];
var out = [ 0, 0, 0, 0, 0, 0 ];

map2.assign( x, y, out, naryFunction( add, 2 ) );

console.log( out );
// => [ 2, 3, 4, 5, 6, 7 ]
`

The method accepts both array-like objects and [ndarray][@stdlib/ndarray/ctor]-like objects.

`javascript
var naryFunction = require( '@stdlib/utils-nary-function' );
var add = require( '@stdlib/number-float64-base-add' );
var array = require( '@stdlib/ndarray-array' );

var opts = {
'dtype': 'generic',
'shape': [ 2, 3 ]
};
var x = array( [ [ 1, 2, 3 ], [ 4, 5, 6 ] ], opts );
var y = array( [ [ 1, 1, 1 ], [ 1, 1, 1 ] ], opts );
var out = array( opts );

map2.assign( x, y, out, naryFunction( add, 2 ) );

var v = out.get( 1, 1 );
// returns 6
`

Input and output arrays must be either all array-like objects or all [ndarray][@stdlib/ndarray/ctor]-like objects. If input and output arrays are array-like objects, all arrays must have the same number of elements.

If input and output arrays are [ndarray][@stdlib/ndarray/ctor]-like objects, the arrays must be [broadcast compatible][@stdlib/ndarray/base/broadcast-shapes]. To map from one or more input [ndarrays][@stdlib/ndarray/ctor] to an output [ndarray][@stdlib/ndarray/ctor] which has the same rank (i.e., dimensionality) and the same number of elements, but which is not [broadcast compatible][@stdlib/ndarray/base/broadcast-shapes], reshape the arrays prior to invocation.

`javascript
var naryFunction = require( '@stdlib/utils-nary-function' );
var add = require( '@stdlib/number-float64-base-add' );
var array = require( '@stdlib/ndarray-array' );

var opts = {
'dtype': 'generic',
'shape': [ 2, 3 ]
};
var x = array( [ [ 1, 2, 3 ], [ 4, 5, 6 ] ], opts );
var y = array( [ [ 1, 1, 1 ], [ 1, 1, 1 ] ], opts );

opts = {
'dtype': 'generic',
'shape': [ 2, 2, 3 ] // broadcast compatible shape
};
var out = array( opts );

map2.assign( x, y, out, naryFunction( add, 2 ) );

var v = out.get( 0, 1, 1 );
// returns 6

v = out.get( 1, 1, 1 );
// returns 6
`

In general, avoid providing output [ndarray][@stdlib/ndarray/ctor]-like objects which are [non-contiguous][@stdlib/ndarray/base/assert/is-contiguous] views containing one or more elements referring to the same memory location. Writing to an overlapping [non-contiguous][@stdlib/ndarray/base/assert/is-contiguous] view is likely to simultaneously affect multiple elements and yield unexpected results.

The applied function is provided the same arguments as with map2.