Fibonacci Number Index

Compute the Fibonacci number index of a single-precision floating-point number.

The Fibonacci number index is given by

where φ is the golden ratio and F > 1.

Installation

npm install @stdlib/math-base-special-fibonacci-indexf

Usage

var fibonacciIndexf = require( '@stdlib/math-base-special-fibonacci-indexf' );

fibonacciIndexf( F )

Computes the Fibonacci number index of a single-precision floating-point number.

var n = fibonacciIndexf( 2 );
// returns 3

n = fibonacciIndexf( 3 );
// returns 4

n = fibonacciIndexf( 5 );
// returns 5

If provided either a non-integer or F_n <= 1, the function returns NaN.

var n = fibonacciIndexf( -1 );
// returns NaN

n = fibonacciIndexf( 3.14 );
// returns NaN

If provided NaN, the function returns NaN.

var n = fibonacciIndexf( NaN );
// returns NaN

Examples

var fibonacciIndexf = require( '@stdlib/math-base-special-fibonacci-indexf' );

var F1;
var F2;
var FN;
var n;
var i;

F1 = 1;
F2 = 1;
for ( i = 3; i < 37; i++ ) {
    FN = F1 + F2;
    F1 = F2;
    F2 = FN;
    n = fibonacciIndexf( FN );
    console.log( 'n(%d) = %d', FN, n );
}

C APIs

Usage

#include "stdlib/math/base/special/fibonacci_indexf.h"

stdlib_base_fibonacci_indexf( F )

Computes the Fibonacci number index of a single-precision floating-point number.

float out = stdlib_base_fibonacci_indexf( 2.0f );
// returns 3.0f

out = stdlib_base_fibonacci_indexf( 3.0f );
// returns 4.0f

The function accepts the following arguments:

• F: [in] float input value.

float stdlib_base_fibonacci_indexf( const float F );

Examples

#include "stdlib/math/base/special/fibonacci_indexf.h"
#include <stdio.h>

int main( void ) {
    const float x[] = { 2.0f, 3.0f, 5.0f, 8.0f };

    float y;
    int i;
    for ( i = 0; i < 4; i++ ) {
        y = stdlib_base_fibonacci_indexf( x[ i ] );
        printf( "fibonacci_indexf(%f) = %f\n", x[ i ], y );
    }
}

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.