feat: table view for follow set

src/utils/follow/mod.rs

@@ -1,6 +1,9 @@
 use crate::utils::follow::builder::FollowBuilder;
 use bnf::{Grammar, Term};
+use itertools::Itertools;
 use std::collections::{HashMap, HashSet};
+use tabled::builder::Builder;
+use tabled::Table;
 
 mod builder;
 
@@ -17,4 +20,58 @@ impl<'grammar> Follow<'grammar> {
         // TODO: remove the unwrap?
         self.follow.get(x).unwrap().iter()
     }
+
+    pub fn tabled(&self) -> Table {
+        let mut table = Builder::new();
+        table.set_header(["Term", "Follow(X)"]);
+        for (term, first) in self
+            .follow
+            .iter()
+            .filter(|(term, _)| matches!(term, Term::Nonterminal(_)))
+            .sorted_by(|a, b| a.0.cmp(b.0))
+        {
+            table.push_record([term.to_string(), first.iter().sorted().join(", ")]);
+        }
+        table.build()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::utils::follow::Follow;
+    use bnf::Term;
+    use std::str::FromStr;
+
+    #[test]
+    fn it_works() {
+        let grammar = r#"
+        <E> ::= <T> <E'>
+        <E'> ::= '+' <T> <E'> | 'ε'
+        <T> ::= <F> <T'>
+        <T'> ::= '*' <F> <T'> | 'ε'
+        <F> ::= '(' <E> ')' | 'id'
+        "#
+        .parse()
+        .unwrap();
+        let start = Term::from_str("<E>").unwrap();
+        let follow = Follow::new(&grammar, &start);
+        insta::assert_display_snapshot!(follow.tabled());
+    }
+
+    #[test]
+    fn test_case_1() {
+        let grammar = r#"
+        <P> ::= <Q> 'id' <R>
+        <Q> ::= '∃' | '∀'
+        <R> ::= <E> '=' <E>
+        <E> ::= <T> <E'>
+        <E'> ::= '+' <T> <E'> | 'ε'
+        <T> ::= '(' <E> ')' | 'id'
+        "#
+        .parse()
+        .unwrap();
+        let start = Term::from_str("<P>").unwrap();
+        let follow = Follow::new(&grammar, &start);
+        insta::assert_display_snapshot!(follow.tabled());
+    }
 }

src/utils/follow/snapshots/context_free__utils__follow__tests__case_1.snap

@@ -0,0 +1,19 @@
+---
+source: src/utils/follow/mod.rs
+expression: follow.tabled()
+---
++------+--------------------+
+| Term | Follow(X)          |
++------+--------------------+
+| <E>  | "$", ")", "="      |
++------+--------------------+
+| <E'> | "$", ")", "="      |
++------+--------------------+
+| <P>  | "$"                |
++------+--------------------+
+| <Q>  | "id"               |
++------+--------------------+
+| <R>  | "$"                |
++------+--------------------+
+| <T>  | "$", ")", "+", "=" |
++------+--------------------+

src/utils/follow/snapshots/context_free__utils__follow__tests__it_works.snap

@@ -0,0 +1,17 @@
+---
+source: src/utils/follow/mod.rs
+expression: follow.tabled()
+---
++------+--------------------+
+| Term | Follow(X)          |
++------+--------------------+
+| <E>  | "$", ")"           |
++------+--------------------+
+| <E'> | "$", ")"           |
++------+--------------------+
+| <F>  | "$", ")", "*", "+" |
++------+--------------------+
+| <T>  | "$", ")", "+"      |
++------+--------------------+
+| <T'> | "$", ")", "+"      |
++------+--------------------+