simple_term_rewriter 0.3.0

A basic interface to rewrite concrete tree terms according to a set of rules
Documentation 
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/*
Copyright 2024 Erwan Mahe (github.com/erwanM974)

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/


use std::hash::Hash;

use std::collections::{HashMap, HashSet};
use std::marker::PhantomData;

use crate::core::terms::term::{LanguageTerm, RewritableLanguageOperatorSymbol};



pub trait TermSymbolMetric<LOS : RewritableLanguageOperatorSymbol> : Clone + PartialEq + Eq + PartialOrd + Copy + Ord + Hash + std::fmt::Display {

    fn measure_nested_depth(&self) -> bool;

    /** 
     * Gathers several metrics from the occurrence of an operator symbol (in a term).
     * **/
    fn from_operator_symbol(op : &LOS) -> HashSet<Self>;

}



pub struct TermMetrics<LOS : RewritableLanguageOperatorSymbol, TSM : TermSymbolMetric<LOS>> {
    phantom : PhantomData<LOS>,
    pub metrics_count : HashMap<TSM,u32>,
    pub term_depth : u32,
    pub max_nested_metrics_depths : HashMap<TSM,u32>
}

impl<LOS : RewritableLanguageOperatorSymbol, TSM : TermSymbolMetric<LOS>> TermMetrics<LOS,TSM> {

    pub fn string_summary(&self) -> Vec<String> {
        let mut mystrings = vec![];
        mystrings.push(format!("term depth : {:}", self.term_depth));
        for (metric,count) in &self.metrics_count {
            mystrings.push(format!("{:} : {:}", metric, count));
        }
        for (metric,nested_depth) in &self.max_nested_metrics_depths {
            mystrings.push(format!("{:}-max-nested-depth : {:}", metric, nested_depth));
        }
        mystrings
    }


    pub fn extract_from_term(term : &LanguageTerm<LOS>) -> Self {
        let mut metrics_count = HashMap::new();
        let (max_nested_metrics_depths, term_depth) = Self::extract_rec(
            term, 
            &mut metrics_count, 
            1, 
            &HashMap::new()
        );

        Self {
            phantom : PhantomData,
            metrics_count,
            term_depth,
            max_nested_metrics_depths
        }
    }

    fn extract_rec(
        term : &LanguageTerm<LOS>,
        metrics_count : &mut HashMap<TSM,u32>,
        parent_depth : u32,
        parent_nested_depths : &HashMap<TSM,u32>
    ) -> (HashMap<TSM,u32>,u32) {
        let mut current_nested_depths = parent_nested_depths.clone();
        for metric in TSM::from_operator_symbol(&term.operator) {
            if let std::collections::hash_map::Entry::Vacant(e) = metrics_count.entry(metric) {
                e.insert(1);
            } else {
                *metrics_count.get_mut(&metric).unwrap() += 1;
            }
            if metric.measure_nested_depth() {
                if let std::collections::hash_map::Entry::Vacant(e) = current_nested_depths.entry(metric) {
                    e.insert(1);
                } else {
                    *current_nested_depths.get_mut(&metric).unwrap() += 1;
                }
            }
        }
        let mut max_depth = parent_depth;
        let mut max_nested_depths = current_nested_depths.clone();
        for sub_term in term.sub_terms.iter() {
            let (child_max_nested_depths,child_max_depth) = Self::extract_rec(
                sub_term, 
                metrics_count, 
                parent_depth + 1, 
                &current_nested_depths
            );
            max_depth = u32::max(max_depth, child_max_depth);
            for (metric,nested_depth) in child_max_nested_depths {
                if max_nested_depths.contains_key(&metric) {
                    let prev = max_nested_depths.get(&metric).unwrap();
                    max_nested_depths.insert(metric, u32::max(*prev, nested_depth));
                } else {
                    max_nested_depths.insert(metric, nested_depth);
                }
            }
        }

        (max_nested_depths,max_depth)
    }
}