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::{Expression, Integral, Negation},
};

use super::DerivationRule;

pub struct IntegralPullOutNegative {}

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

        let Expression::Negation(ref integrand) = integral.integrand() else {
            return vec![];
        };

        vec![(
            Negation::of(Integral::of(integrand.exp(), integral.variable())),
            Argument::new(
                String::from("Pull out negative (constant)"),
                vec![input],
                self.name(),
            ),
        )]
    }

    fn name(&self) -> String {
        String::from("IntegralPullOutNegative")
    }
}

#[cfg(test)]
mod tests {
    use crate::convenience_expressions::v;

    use super::*;

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

        let start = Integral::of(Negation::of(v("x")), v("x"));
        let result = rule.apply(start).first().unwrap().0.clone();

        assert_eq!(result, Negation::of(Integral::of(v("x"), v("x"))));
    }
}