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use std::fmt::{self, Display, Formatter};
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use thiserror::Error;

            

        

            

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use crate::ast::Expression;

            

        

            

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#[derive(Debug, Error)]

            

        

            

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pub enum RuleApplicationError {

            

        

            

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    #[error("Rule is not applicable")]

            

        

            

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    RuleNotApplicable,

            

        

            

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}

            

        

            

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#[derive(Clone, Debug)]

            

        

            

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pub struct Rule<'a> {

            

        

            

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    pub name: &'a str,

            

        

            

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    pub application: fn(&Expression) -> Result<Expression, RuleApplicationError>,

            

        

            

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}

            

        

            

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impl<'a> Rule<'a> {

            

        

            

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    pub fn new(

            

        

            

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        name: &'a str,

            

        

            

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        application: fn(&Expression) -> Result<Expression, RuleApplicationError>,

            

        

            

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    ) -> Self {

            

        

            

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        Self { name, application }

            

        

            

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    }

            

        

            

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    pub fn apply(&self, expr: &Expression) -> Result<Expression, RuleApplicationError> {

            

        

            

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        (self.application)(expr)

            

        

            

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    }

            

        

            

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}

            

        

            

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impl<'a> Display for Rule<'a> {

            

        

            

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    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {

            

        

            

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        write!(f, "{}", self.name)

            

        

            

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    }

            

        

            

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}