Create Polynomial struct

[dawnandrew100]

In the wise words of people far smarter than me (thank you kind people of the rustfully discord), a polynomial struct should be added to this repository.

An example implementation (all f64 might have to be replaced with generic variable to allow for floats and ints)

use crate::polynomials::{ascii_letters, Term, core::PolynomialError};
use crate::{eval_polynomial, parse_polynomial, parse_multivar, eval_multivar};
use std::str::FromStr;

struct Polynomial {
    coefficents: Vec<f64>,
}

pub struct MultivariatePolynomial {
    terms: Vec<Term>,
}

// inherient methods
impl Polynomial {
    fn from(&self, coefficents: &str) -> Result<Self, PolynomialError> {
        let parsed = parse_polynomial(coefficents)?;
        Ok(Self {
            coefficents: parsed,
        })
    }
    fn solve(&self, point: f64) -> f64 {
        eval_polynomial(point, &self.coefficents)
    }
}

impl MultivariatePolynomial {
    fn from(&self, coefficents: &str) -> Result<Self, PolynomialError> {
        // change parse_multivar output from option to Result
        let parsed = parse_multivar(coefficents)?; <- parameters need to be adjusted 
        Ok(Self {
            terms: parsed,
        })
    }
    fn solve(&self, point: f64) -> f64 {
        // Need to create eval_multivar function
        eval_multivar(point, &self.terms)
    }
}

// trait implementation
impl FromStr for Polynomial {
    type Err = ();

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        todo!("parse string into self or error")
    }
}

impl FromStr for MultivariatePolynomial {
    type Err = ();

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        todo!("parse string into self or error")
    }
}

After creating the struct, it can be added as an output of parse_polynomial and parse_multivar and this struct should be the input of the bisection and nrm functions (replacing the string inputs that are parsed within the functions)