differentiate.rs

use std::fmt;

/// representing each term of the polynomial
struct Nomial {
    coefficient: f64,
    power: f64,
}

impl Nomial {
    fn new(coefficient: f64, power: f64) -> Self {
        Nomial {
            coefficient,
            power,
        }
    }
}

impl fmt::Debug for Nomial {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let coef: String = if self.coefficient == 1.0 {
            if self.power != 0.0 {
                "".into()
            } else {
                "1".into()
            }
        } else {
            self.coefficient.to_string()
        };

        let power: String = if self.power == 0.0 {
            "".into()
        } else if self.power == 1.0 {
            "x".into()
        } else {
            format!("x^{}", self.power.to_string())
        };

        write!(f, "{}{}", coef, power)
    }
}

type polynomial = Vec<Nomial>;

fn differentiate(pl: &polynomial) -> polynomial {
    pl.iter()
        .map(|x| Nomial {
            coefficient: x.coefficient * x.power,
            power: x.power - 1.0,
        })
        .collect()
}

fn main() {
    let x = Nomial {
        coefficient: 1.0,
        power: 1.0,
    };
    let twox = Nomial::new(5.0, 2.0);
    let poly = vec![x, twox];
    let poly = differentiate(&poly);
    println!("{:?}", poly);
}