time-to-botec/squiggle/node_modules/@stdlib/math/iter/tools/map2/README.md

iterMap2

Create an iterator which invokes a binary function accepting numeric arguments for each iterated value.

Usage

var iterMap2 = require( '@stdlib/math/iter/tools/map2' );

iterMap2( iter0, iter1, fcn[, options] )

Returns an iterator which invokes a binary function accepting numeric arguments for each iterated value.

var array2iterator = require( '@stdlib/array/to-iterator' );
var copysign = require( '@stdlib/math/base/special/copysign' );

var it1 = array2iterator( [ 1.0, 2.0, 3.0, 4.0 ] );
var it2 = array2iterator( [ 1.0, -1.0, -1.0, 1.0 ] );

var it = iterMap2( it1, it2, copysign );
// returns <Object>

var r = it.next().value;
// returns 1.0

r = it.next().value;
// returns -2.0

r = it.next().value;
// returns -3.0

// ...

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.

The invoked function is provided two arguments:

• x: iterated value from first input iterator.
• y: iterated value from second input iterator.

var array2iterator = require( '@stdlib/array/to-iterator' );

function fcn( x, y ) {
    return x + y + 10;
}

var it1 = array2iterator( [ 1, 2, 3, 4 ] );
var it2 = array2iterator( [ 1, 2, 3, 4 ] );

var it = iterMap2( it1, it2, fcn );
// returns <Object>

var r = it.next().value;
// returns 12

r = it.next().value;
// returns 14

r = it.next().value;
// returns 16

// ...

The function supports the following options:

• invalid: return value when an input iterator yields a non-numeric value. Default: NaN.

By default, the function returns an iterator which returns NaN when an input iterator yields a non-numeric value. To specify a different return value, set the invalid option.

var array2iterator = require( '@stdlib/array/to-iterator' );
var copysign = require( '@stdlib/math/base/special/copysign' );

var it1 = array2iterator( [ '1.0', '2.0', '3.0' ] );
var it2 = array2iterator( [ 1.0, 2.0, 3.0 ] );

var opts = {
    'invalid': null
};
var it = iterMap2( it1, it2, copysign, opts );
// returns <Object>

var v = it.next().value;
// returns null

v = it.next().value;
// returns null

// ...

If provided a numeric value as an iterator argument, the value is broadcast as an infinite iterator which always returns the provided value.

var array2iterator = require( '@stdlib/array/to-iterator' );
var copysign = require( '@stdlib/math/base/special/copysign' );

var it1 = array2iterator( [ 1.0, 2.0 ] );

var it = iterMap2( it1, -4.0, copysign );
// returns <Object>

var v = it.next().value;
// returns -1.0

v = it.next().value;
// returns -2.0

var bool = it.next().done;
// returns true

Notes

• If an iterated value is non-numeric (including NaN), the returned iterator returns NaN. If non-numeric iterated values are possible, you are advised to provide an iterator which type checks and handles non-numeric values accordingly.
• The length of the returned iterator is equal to the length of the shortest provided iterator. In other words, the returned iterator ends once one of the provided iterators ends.
• If an environment supports Symbol.iterator and a provided iterator is iterable, the returned iterator is iterable.

Examples

var randu = require( '@stdlib/random/iter/randu' );
var uniform = require( '@stdlib/random/iter/uniform' );
var copysign = require( '@stdlib/math/base/special/copysign' );
var iterMap2 = require( '@stdlib/math/iter/tools/map2' );

// Create seeded iterators for generating pseudorandom numbers:
var rand1 = randu({
    'seed': 1234,
    'iter': 10
});

var rand2 = uniform( -1.0, 1.0, {
    'seed': 1234,
    'iter': 10
});

// Create an iterator which consumes the pseudorandom number iterators:
var it = iterMap2( rand1, rand2, copysign );

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