ihateintegrals 0.1.2

A computer algebra library for solving integrals.
Documentation 
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use std::rc::Rc;

use crate::{
    argument::Argument,
    expressions::{product::product_of_iter, Expression, Fraction},
};

use super::DerivationRule;

/**
* (a/b) * (c/d) = ac/bd
*/
pub struct MultiplyFractions {}

impl DerivationRule for MultiplyFractions {
    fn apply(&self, input: Expression) -> Vec<(Expression, Rc<Argument>)> {
        let product = match input {
            Expression::Product(ref p) => p,
            _ => return vec![],
        };

        let (fractions, not): (Vec<&Expression>, Vec<&Expression>) = product
            .factors()
            .iter()
            .partition(|exp| matches!(exp, Expression::Fraction(_)));

        if fractions.is_empty() {
            return vec![];
        }

        let result_fraction = Fraction::of(
            product_of_iter(&mut fractions.iter().map(|f| match f {
                Expression::Fraction(f) => f.numerator(),
                _ => panic!(),
            })),
            product_of_iter(&mut fractions.iter().map(|f| match f {
                Expression::Fraction(f) => f.denominator(),
                _ => panic!(),
            })),
        );

        vec![(
            product_of_iter(
                &mut [result_fraction]
                    .into_iter()
                    .chain(&mut not.into_iter().cloned()),
            ),
            Argument::new(String::from("Multiply fractions"), vec![input], self.name()),
        )]
    }
    fn name(&self) -> String {
        String::from("MultiplyFractions")
    }
}