ihateintegrals 0.1.2

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

use crate::{
    argument::Argument,
    convenience_expressions::sum_of_iter,
    expressions::{Expression, Integral},
};

use super::DerivationRule;

/**
* Break integrals over addition.
*/
pub struct IntegralSumRule {}

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

        let sum = match integral.integrand() {
            Expression::Sum(s) => s,
            _ => return vec![],
        };

        vec![(
            sum_of_iter(
                &mut sum
                    .terms()
                    .iter()
                    .map(|term| Integral::of(term.clone(), integral.variable())),
            ),
            Argument::new(
                String::from("Split integral over addition"),
                vec![input],
                self.name(),
            ),
        )]
    }
    fn name(&self) -> String {
        String::from("IntegralSumRule")
    }
}

#[cfg(test)]
mod tests {
    use crate::{
        convenience_expressions::{i, v},
        derivation_rules::DerivationRule,
        expressions::{sum::sum_of, Integral},
    };

    use super::IntegralSumRule;

    #[test]
    fn test_1() {
        let rule = IntegralSumRule {};

        let start = Integral::of(sum_of(&[i(1), i(2)]), v("x"));
        let result = rule.apply(start).first().unwrap().0.clone();

        assert_eq!(
            result,
            sum_of(&[Integral::of(i(1), v("x")), Integral::of(i(2), v("x"))])
        );
    }
}