logicaffeine_language/
visitor.rs

1//! AST visitor pattern for traversing logical expressions.
2//!
3//! This module provides a visitor trait for walking the AST without mutation.
4//! It follows the standard visitor pattern with `walk_*` functions that handle
5//! recursive traversal and `visit_*` methods that can be overridden.
6//!
7//! # Usage
8//!
9//! Implement [`Visitor`] and override the `visit_*` methods you need:
10//!
11//! ```no_run
12//! # use logicaffeine_base::Symbol;
13//! # use logicaffeine_language::ast::Term;
14//! # use logicaffeine_language::visitor::{Visitor, walk_term};
15//! struct VariableCollector {
16//!     vars: Vec<Symbol>,
17//! }
18//!
19//! impl<'a> Visitor<'a> for VariableCollector {
20//!     fn visit_term(&mut self, term: &'a Term<'a>) {
21//!         if let Term::Variable(sym) = term {
22//!             self.vars.push(*sym);
23//!         }
24//!         walk_term(self, term);
25//!     }
26//! }
27//! ```
28
29use crate::ast::{LogicExpr, NounPhrase, Term};
30
31/// Trait for visiting AST nodes.
32pub trait Visitor<'a>: Sized {
33    fn visit_expr(&mut self, expr: &'a LogicExpr<'a>) {
34        walk_expr(self, expr);
35    }
36
37    fn visit_term(&mut self, term: &'a Term<'a>) {
38        walk_term(self, term);
39    }
40
41    fn visit_np(&mut self, np: &'a NounPhrase<'a>) {
42        walk_np(self, np);
43    }
44}
45
46pub fn walk_expr<'a, V: Visitor<'a>>(v: &mut V, expr: &'a LogicExpr<'a>) {
47    match expr {
48        LogicExpr::Predicate { args, .. } => {
49            for arg in *args {
50                v.visit_term(arg);
51            }
52        }
53
54        LogicExpr::Identity { left, right } => {
55            v.visit_term(left);
56            v.visit_term(right);
57        }
58
59        LogicExpr::Metaphor { tenor, vehicle } => {
60            v.visit_term(tenor);
61            v.visit_term(vehicle);
62        }
63
64        LogicExpr::Quantifier { body, .. } => {
65            v.visit_expr(body);
66        }
67
68        LogicExpr::Categorical(data) => {
69            v.visit_np(&data.subject);
70            v.visit_np(&data.predicate);
71        }
72
73        LogicExpr::Relation(data) => {
74            v.visit_np(&data.subject);
75            v.visit_np(&data.object);
76        }
77
78        LogicExpr::Modal { operand, .. } => {
79            v.visit_expr(operand);
80        }
81
82        LogicExpr::Temporal { body, .. } => {
83            v.visit_expr(body);
84        }
85
86        LogicExpr::TemporalBinary { left, right, .. } => {
87            v.visit_expr(left);
88            v.visit_expr(right);
89        }
90
91        LogicExpr::Aspectual { body, .. } => {
92            v.visit_expr(body);
93        }
94
95        LogicExpr::Voice { body, .. } => {
96            v.visit_expr(body);
97        }
98
99        LogicExpr::BinaryOp { left, right, .. } => {
100            v.visit_expr(left);
101            v.visit_expr(right);
102        }
103
104        LogicExpr::UnaryOp { operand, .. } => {
105            v.visit_expr(operand);
106        }
107
108        LogicExpr::Question { body, .. } => {
109            v.visit_expr(body);
110        }
111
112        LogicExpr::YesNoQuestion { body } => {
113            v.visit_expr(body);
114        }
115
116        LogicExpr::Atom(_) => {}
117
118        LogicExpr::Lambda { body, .. } => {
119            v.visit_expr(body);
120        }
121
122        LogicExpr::App { function, argument } => {
123            v.visit_expr(function);
124            v.visit_expr(argument);
125        }
126
127        LogicExpr::Intensional { content, .. } => {
128            v.visit_expr(content);
129        }
130
131        LogicExpr::Event { predicate, .. } => {
132            v.visit_expr(predicate);
133        }
134
135        LogicExpr::NeoEvent(data) => {
136            for (_, term) in data.roles.iter() {
137                v.visit_term(term);
138            }
139        }
140
141        LogicExpr::Imperative { action } => {
142            v.visit_expr(action);
143        }
144
145        LogicExpr::SpeechAct { content, .. } => {
146            v.visit_expr(content);
147        }
148
149        LogicExpr::Counterfactual { antecedent, consequent } => {
150            v.visit_expr(antecedent);
151            v.visit_expr(consequent);
152        }
153
154        LogicExpr::Causal { effect, cause } => {
155            v.visit_expr(cause);
156            v.visit_expr(effect);
157        }
158
159        LogicExpr::Comparative { subject, object, .. } => {
160            v.visit_term(subject);
161            v.visit_term(object);
162        }
163
164        LogicExpr::Superlative { subject, .. } => {
165            v.visit_term(subject);
166        }
167
168        LogicExpr::Scopal { body, .. } => {
169            v.visit_expr(body);
170        }
171
172        LogicExpr::Control { subject, object, infinitive, .. } => {
173            v.visit_term(subject);
174            if let Some(obj) = object {
175                v.visit_term(obj);
176            }
177            v.visit_expr(infinitive);
178        }
179
180        LogicExpr::Presupposition { assertion, presupposition } => {
181            v.visit_expr(assertion);
182            v.visit_expr(presupposition);
183        }
184
185        LogicExpr::Focus { focused, scope, .. } => {
186            v.visit_term(focused);
187            v.visit_expr(scope);
188        }
189
190        LogicExpr::TemporalAnchor { body, .. } => {
191            v.visit_expr(body);
192        }
193
194        LogicExpr::Distributive { predicate } => {
195            v.visit_expr(predicate);
196        }
197
198        LogicExpr::GroupQuantifier { restriction, body, .. } => {
199            v.visit_expr(restriction);
200            v.visit_expr(body);
201        }
202    }
203}
204
205pub fn walk_term<'a, V: Visitor<'a>>(v: &mut V, term: &'a Term<'a>) {
206    match term {
207        Term::Constant(_) | Term::Variable(_) | Term::Sigma(_) | Term::Intension(_) | Term::Value { .. } => {}
208
209        Term::Function(_, args) => {
210            for arg in *args {
211                v.visit_term(arg);
212            }
213        }
214
215        Term::Group(members) => {
216            for m in *members {
217                v.visit_term(m);
218            }
219        }
220
221        Term::Possessed { possessor, .. } => {
222            v.visit_term(possessor);
223        }
224
225        Term::Proposition(expr) => {
226            v.visit_expr(expr);
227        }
228    }
229}
230
231pub fn walk_np<'a, V: Visitor<'a>>(v: &mut V, np: &'a NounPhrase<'a>) {
232    if let Some(poss) = np.possessor {
233        v.visit_np(poss);
234    }
235    for pp in np.pps.iter() {
236        v.visit_expr(pp);
237    }
238}
239
240#[cfg(test)]
241mod tests {
242    use super::*;
243    use logicaffeine_base::Symbol;
244
245    struct VariableCollector {
246        variables: Vec<Symbol>,
247    }
248
249    impl<'a> Visitor<'a> for VariableCollector {
250        fn visit_term(&mut self, term: &'a Term<'a>) {
251            if let Term::Variable(sym) = term {
252                self.variables.push(*sym);
253            }
254            walk_term(self, term);
255        }
256    }
257
258    struct ExprCounter {
259        count: usize,
260    }
261
262    impl<'a> Visitor<'a> for ExprCounter {
263        fn visit_expr(&mut self, expr: &'a LogicExpr<'a>) {
264            self.count += 1;
265            walk_expr(self, expr);
266        }
267    }
268
269    #[test]
270    fn variable_collector_finds_variables() {
271        use logicaffeine_base::Arena;
272        use logicaffeine_base::Interner;
273
274        let mut interner = Interner::new();
275        let x = interner.intern("x");
276        let y = interner.intern("y");
277
278        let term_arena: Arena<Term> = Arena::new();
279        let terms = term_arena.alloc_slice([Term::Variable(x), Term::Variable(y)]);
280
281        let expr_arena: Arena<LogicExpr> = Arena::new();
282        let pred = interner.intern("P");
283        let expr = expr_arena.alloc(LogicExpr::Predicate { name: pred, args: terms, world: None });
284
285        let mut collector = VariableCollector { variables: vec![] };
286        collector.visit_expr(expr);
287
288        assert_eq!(collector.variables.len(), 2);
289        assert!(collector.variables.contains(&x));
290        assert!(collector.variables.contains(&y));
291    }
292
293    #[test]
294    fn expr_counter_counts_nested() {
295        use logicaffeine_base::Arena;
296        use logicaffeine_base::Interner;
297        use crate::token::TokenType;
298
299        let mut interner = Interner::new();
300        let p = interner.intern("P");
301        let q = interner.intern("Q");
302
303        let expr_arena: Arena<LogicExpr> = Arena::new();
304
305        let left = expr_arena.alloc(LogicExpr::Atom(p));
306        let right = expr_arena.alloc(LogicExpr::Atom(q));
307        let binary = expr_arena.alloc(LogicExpr::BinaryOp {
308            left,
309            op: TokenType::And,
310            right,
311        });
312
313        let mut counter = ExprCounter { count: 0 };
314        counter.visit_expr(binary);
315
316        assert_eq!(counter.count, 3);
317    }
318}
logicaffeine_language/visitor.rs

logicaffeine_language/
visitor.rs
