Function extract_arg 

pub fn extract_arg<const N: usize, T>(
    lisp: &Lisp<N>,
    args: ArenaIndex,
) -> Result<(T, ArenaIndex), ArenaError>
where
    T: FromLisp<N>,

Extract a single argument from a Lisp argument list.

Example

use grift_eval::{extract_arg, Lisp, ArenaIndex, ArenaResult};

fn example<const N: usize>(lisp: &Lisp<N>, args: ArenaIndex) -> ArenaResult<(isize, ArenaIndex)> {
    extract_arg::<N, isize>(lisp, args)
}