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use conjure_cp::rule_engine::SubmodelZipper;
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use conjure_cp::{
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    ast::{Expression, SymbolTable},
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    rule_engine::{ApplicationError::RuleNotApplicable, ApplicationResult, Reduction},
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};
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/// Converts the rule function `rule` to a rule that applies `rule` bottom-up to every expression

            

        

            

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/// in the current sub-model.

            

        

            

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pub fn as_bottom_up(

            

        

            

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    rule: impl Fn(&Expression, &SymbolTable) -> ApplicationResult,

            

        

            

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) -> impl Fn(&Expression, &SymbolTable) -> ApplicationResult {

            

        

            

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    Box::new(move |expr: &Expression, symbols: &SymbolTable| {

            

        

            

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        // global rule

            

        

            

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        if !matches!(expr, Expression::Root(_, _)) {

            

        

            

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            return Err(RuleNotApplicable);

            

        

            

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        };

            

        

            

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        // traverse bottom up within the current sub-model, applying the rule.

            

        

            

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        let mut symbols = symbols.clone();

            

        

            

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        let mut new_tops = vec![];

            

        

            

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        let mut done_something = false;

            

        

            

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        let mut zipper = SubmodelZipper::new(expr.clone());

            

        

            

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        while zipper.go_down().is_some() {}

            

        

            

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        loop {

            

        

            

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            // go right and to the bottom of that subtree

            

        

            

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            //

            

        

            

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            // once we have ran out of siblings, go_up.

            

        

            

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            if zipper.go_right().is_some() {

            

        

            

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                while zipper.go_down().is_some() {}

            

        

            

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            } else if zipper.go_up().is_none() {

            

        

            

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                // cannot go up anymore, at the root

            

        

            

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                break;

            

        

            

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            }

            

        

            

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            let expr = zipper.focus();

            

        

            

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            if let Ok(mut reduction) = rule(expr, &symbols) {

            

        

            

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                zipper.replace_focus(reduction.new_expression);

            

        

            

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                symbols.extend(reduction.symbols);

            

        

            

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                new_tops.append(&mut reduction.new_top);

            

        

            

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                done_something = true;

            

        

            

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            }

            

        

            

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        }

            

        

            

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        let root_expr = zipper.rebuild_root();

            

        

            

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        if done_something {

            

        

            

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            Ok(Reduction::new(root_expr, new_tops, symbols))

            

        

            

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        } else {

            

        

            

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            Err(RuleNotApplicable)

            

        

            

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        }

            

        

            

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    })

            

        

            

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}