108 lines
3.2 KiB
Rust
108 lines
3.2 KiB
Rust
extern crate rand;
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use rand::{seq::SliceRandom, thread_rng};
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use std::collections::HashMap;
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pub trait Purrchance {
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fn eval(&self, g: &Grammar) -> Option<String>;
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}
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pub enum Symbol {
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Terminal(String),
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NonTerminal(String),
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}
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impl Purrchance for Symbol {
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fn eval(&self, g: &Grammar) -> Option<String> {
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match self {
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Symbol::Terminal(s) => Some(s.to_string()),
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Symbol::NonTerminal(label) => g.0.get(label)?.eval(g),
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}
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}
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}
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pub struct Expr(Vec<Symbol>);
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impl Purrchance for Expr {
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fn eval(&self, g: &Grammar) -> Option<String> {
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Some(self.0.iter().map(|sym| sym.eval(g)).collect::<Option<Vec<String>>>()?.join(""))
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}
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}
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pub struct List(Vec<(Expr, f64)>);
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impl Purrchance for List {
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fn eval(&self, g: &Grammar) -> Option<String> {
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self.0.choose_weighted(&mut thread_rng(), |item| item.1).ok()?.0.eval(g)
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}
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}
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pub struct Grammar(HashMap<String,List>);
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn eval_terminal() {
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let sym = Symbol::Terminal("hello world".to_string());
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let g = Grammar(HashMap::new());
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assert_eq!(sym.eval(&g), Some("hello world".to_string()));
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}
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#[test]
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fn eval_terminals_expr() {
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let sym1 = Symbol::Terminal("hell".to_string());
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let sym2 = Symbol::Terminal("o world".to_string());
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let expr = Expr(vec![sym1, sym2]);
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let g = Grammar(HashMap::new());
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assert_eq!(expr.eval(&g), Some("hello world".to_string()));
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}
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#[test]
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fn eval_single_terminals_expr_list() {
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let sym1 = Symbol::Terminal("hell".to_string());
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let sym2 = Symbol::Terminal("o world".to_string());
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let expr = Expr(vec![sym1, sym2]);
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let list = List(vec![(expr, 1.0)]);
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let g = Grammar(HashMap::new());
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assert_eq!(list.eval(&g), Some("hello world".to_string()));
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}
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#[test]
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fn eval_multiple_terminals_expr_list() {
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let sym1 = Symbol::Terminal("hello".to_string());
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let sym2 = Symbol::Terminal("goodbye".to_string());
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let list = List(vec![(Expr(vec![sym1]), 1.0), (Expr(vec![sym2]), 1.0)]);
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let g = Grammar(HashMap::new());
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assert!(vec![Some("hello".to_string()), Some("goodbye".to_string())].contains(&list.eval(&g)));
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}
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#[test]
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fn eval_empty_list() {
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let list = List(vec![]);
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let g = Grammar(HashMap::new());
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assert_eq!(list.eval(&g), None);
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}
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#[test]
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fn eval_valid_nonterminal() {
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let term = Symbol::Terminal("hello world".to_string());
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let list = List(vec![(Expr(vec![term]), 1.0)]);
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let mut g = Grammar(HashMap::new());
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g.0.insert("output".to_string(), list);
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let nt = Symbol::NonTerminal("output".to_string());
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assert_eq!(nt.eval(&g), Some("hello world".to_string()));
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}
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#[test]
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fn eval_missing_nonterminal() {
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let term = Symbol::Terminal("hello world".to_string());
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let list = List(vec![(Expr(vec![term]), 1.0)]);
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let mut g = Grammar(HashMap::new());
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g.0.insert("output".to_string(), list);
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let nt = Symbol::NonTerminal("missing".to_string());
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assert_eq!(nt.eval(&g), None);
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}
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}
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