iterNegaFibonacciSeq

Create an iterator which generates a negaFibonacci sequence.

The negaFibonacci numbers are the integer sequence

$$0, 1, -1, 2, -3, 5, -8, 13, -21, 34, -55, 89, -144, \ldots$$

The sequence is defined by the recurrence relation

$$F_{n-2} = F_{n} - F_{n-1}$$

which yields

$$F_{-n} = (-1)^{n+1} F_n$$

with seed values F_0 = 0 and F_{-1} = 1.

Usage

var iterNegaFibonacciSeq = require( '@stdlib/math/iter/sequences/negafibonacci' );

iterNegaFibonacciSeq( [options] )

Returns an iterator which generates a negaFibonacci sequence.

var it = iterNegaFibonacciSeq();
// returns <Object>

var v = it.next().value;
// returns 0

v = it.next().value;
// returns 1

v = it.next().value;
// returns -1

// ...

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 function supports the following options:

• iter: number of iterations. Default: 79.

The returned iterator can only generate the first 79 negaFibonacci numbers, as larger Fibonacci numbers cannot be safely represented in double-precision floating-point format. By default, the function returns an iterator which generates all 79 numbers. To limit the number of iterations, set the iter option.

var opts = {
    'iter': 2
};
var it = iterNegaFibonacciSeq( opts );
// returns <Object>

var v = it.next().value;
// returns 0

v = it.next().value;
// returns 1

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

Notes

• If an environment supports Symbol.iterator, the returned iterator is iterable.

Examples

var iterNegaFibonacciSeq = require( '@stdlib/math/iter/sequences/negafibonacci' );

// Create an iterator:
var it = iterNegaFibonacciSeq();

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

---

See Also

• @stdlib/math/base/special/negafibonacci: compute the nth negaFibonacci number.
• @stdlib/math/iter/sequences/fibonacci: create an iterator which generates a Fibonacci sequence.
• @stdlib/math/iter/sequences/nonfibonacci: create an iterator which generates a non-Fibonacci integer sequence.