nerdamer.fib(x: ExpressionInput): Expression
Computes the Fibonacci number for an integer index.
Integer inputs are evaluated exactly, including negative indices through the
negafibonacci identity. Symbolic and non-integer inputs remain unevaluated.
Returns
Expression — The exact Fibonacci number for an integer input, or symbolic `fib(x)`.
Examples
fibonacci(10).text() // "55"
fibonacci(-4).text() // "-3"
fibonacci('x').text() // "fib(x)"
