diff --git a/src/bnf.rs b/src/bnf.rs
index 20f9dc6..4de5862 100644
--- a/src/bnf.rs
+++ b/src/bnf.rs
@@ -1,4 +1,6 @@
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub enum Bnf {
     Production,
+    Choice(Vec<Bnf>),
+    Unknown,
 }
diff --git a/src/choice/mod.rs b/src/choice/mod.rs
index 781a3b8..f3ff6a3 100644
--- a/src/choice/mod.rs
+++ b/src/choice/mod.rs
@@ -1,3 +1,4 @@
+use crate::bnf::Bnf;
 use crate::parser::{ParseResult, Parser, ParserInput};
 
 pub fn choice2<P1, P2, I, O, E>(parser1: P1, parser2: P2) -> impl Parser<I, O, E>
@@ -12,16 +13,19 @@ where
     }
 }
 
-pub fn choice<C, I, O, E>(choices: C) -> impl Parser<I, O, E>
+pub fn choice<C, I, O, E>(choices: C) -> (impl Parser<I, O, E>, Bnf)
 where
     C: Choice<I, O, E>,
     I: ParserInput + Clone,
 {
-    move |input| choices.parse(input)
+    let bnf = choices.bnf();
+    (move |input| choices.parse(input), bnf)
 }
 
 pub trait Choice<I: Clone, O, E> {
     fn parse(&self, input: I) -> ParseResult<I, O, E>;
+
+    fn bnf(&self) -> Bnf;
 }
 
 impl<I, O, E, P1, P2> Choice<I, O, E> for (P1, P2)
@@ -34,6 +38,16 @@ where
         let parsers = vec![&self.0 as &dyn Parser<I, O, E>, &self.1];
         choice_loop(input, parsers)
     }
+
+    fn bnf(&self) -> Bnf {
+        let parsers = vec![&self.0 as &dyn Parser<I, O, E>, &self.1];
+        Bnf::Choice(
+            parsers
+                .into_iter()
+                .map(|p| p.bnf().unwrap_or(Bnf::Unknown))
+                .collect(),
+        )
+    }
 }
 
 impl<I, O, E, P1, P2, P3> Choice<I, O, E> for (P1, P2, P3)
@@ -47,6 +61,16 @@ where
         let parsers = vec![&self.0 as &dyn Parser<I, O, E>, &self.1, &self.2];
         choice_loop(input, parsers)
     }
+
+    fn bnf(&self) -> Bnf {
+        let parsers = vec![&self.0 as &dyn Parser<I, O, E>, &self.1, &self.2];
+        Bnf::Choice(
+            parsers
+                .into_iter()
+                .map(|p| p.bnf().unwrap_or(Bnf::Unknown))
+                .collect(),
+        )
+    }
 }
 
 impl<I, O, E, P1, P2, P3, P4> Choice<I, O, E> for (P1, P2, P3, P4)
@@ -61,6 +85,16 @@ where
         let parsers = vec![&self.0 as &dyn Parser<I, O, E>, &self.1, &self.2, &self.3];
         choice_loop(input, parsers)
     }
+
+    fn bnf(&self) -> Bnf {
+        let parsers = vec![&self.0 as &dyn Parser<I, O, E>, &self.1, &self.2, &self.3];
+        Bnf::Choice(
+            parsers
+                .into_iter()
+                .map(|p| p.bnf().unwrap_or(Bnf::Unknown))
+                .collect(),
+        )
+    }
 }
 
 impl<I, O, E, P1, P2, P3, P4, P5> Choice<I, O, E> for (P1, P2, P3, P4, P5)
@@ -82,6 +116,22 @@ where
         ];
         choice_loop(input, parsers)
     }
+
+    fn bnf(&self) -> Bnf {
+        let parsers = vec![
+            &self.0 as &dyn Parser<I, O, E>,
+            &self.1,
+            &self.2,
+            &self.3,
+            &self.4,
+        ];
+        Bnf::Choice(
+            parsers
+                .into_iter()
+                .map(|p| p.bnf().unwrap_or(Bnf::Unknown))
+                .collect(),
+        )
+    }
 }
 
 impl<I, O, E, P1, P2, P3, P4, P5, P6> Choice<I, O, E> for (P1, P2, P3, P4, P5, P6)
@@ -105,6 +155,23 @@ where
         ];
         choice_loop(input, parsers)
     }
+
+    fn bnf(&self) -> Bnf {
+        let parsers = vec![
+            &self.0 as &dyn Parser<I, O, E>,
+            &self.1,
+            &self.2,
+            &self.3,
+            &self.4,
+            &self.5,
+        ];
+        Bnf::Choice(
+            parsers
+                .into_iter()
+                .map(|p| p.bnf().unwrap_or(Bnf::Unknown))
+                .collect(),
+        )
+    }
 }
 
 fn choice_loop<I, O, E>(input: I, parsers: Vec<&dyn Parser<I, O, E>>) -> ParseResult<I, O, E>
diff --git a/src/lib.rs b/src/lib.rs
index f172bc1..acc8164 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,6 +5,8 @@ mod parser;
 pub mod primitives;
 pub mod sequence;
 
+#[cfg(test)]
+use bnf::Bnf;
 pub use parser::{ParseResult, Parser, ParserInput};
 
 #[cfg(test)]
@@ -221,4 +223,10 @@ mod tests {
         let parsed_json = json_object().parse(test_json);
         assert!(parsed_json.is_ok());
     }
+
+    #[test]
+    fn bnf_representation() {
+        let bnf = json_object().bnf().unwrap();
+        assert_eq!(bnf, Bnf::Production);
+    }
 }
diff --git a/src/parser/boxed_parser.rs b/src/parser/boxed_parser.rs
index a3b3e68..d759a8b 100644
--- a/src/parser/boxed_parser.rs
+++ b/src/parser/boxed_parser.rs
@@ -20,7 +20,6 @@ where
             inner: Box::new(inner),
         }
     }
-
 }
 
 impl<'a, I: ParserInput, O, E> Parser<I, O, E> for BoxedParser<'a, I, O, E> {
@@ -32,7 +31,10 @@ impl<'a, I: ParserInput, O, E> Parser<I, O, E> for BoxedParser<'a, I, O, E> {
         self.inner.bnf()
     }
 
-    fn boxed<'b>(self) -> BoxedParser<'b, I, O, E> where Self: Sized + 'b {
+    fn boxed<'b>(self) -> BoxedParser<'b, I, O, E>
+    where
+        Self: Sized + 'b,
+    {
         self
     }
 }
diff --git a/src/parser/mod.rs b/src/parser/mod.rs
index dea519b..13397ca 100644
--- a/src/parser/mod.rs
+++ b/src/parser/mod.rs
@@ -23,7 +23,10 @@ where
         None
     }
 
-    fn boxed<'a>(self) -> BoxedParser<'a, I, O, E> where Self: Sized + 'a {
+    fn boxed<'a>(self) -> BoxedParser<'a, I, O, E>
+    where
+        Self: Sized + 'a,
+    {
         BoxedParser::new(self)
     }
 
@@ -71,8 +74,7 @@ where
         E: 'a,
         P: Parser<I, O2, E> + 'a,
     {
-        crate::sequence::tuple2(self, next_parser)
-            .map(|(_, next_output)| next_output)
+        crate::sequence::tuple2(self, next_parser).map(|(_, next_output)| next_output)
     }
 
     fn then_ignore<'a, P, O2>(self, next_parser: P) -> BoxedParser<'a, I, O, E>
@@ -84,8 +86,7 @@ where
         E: 'a,
         P: Parser<I, O2, E> + 'a,
     {
-        crate::sequence::tuple2(self, next_parser)
-            .map(|(this_output, _)| this_output)
+        crate::sequence::tuple2(self, next_parser).map(|(this_output, _)| this_output)
     }
 
     fn delimited<'a, P1, O1, P2, O2>(self, left: P1, right: P2) -> BoxedParser<'a, I, O, E>
@@ -149,12 +150,12 @@ where
     }
 }
 
-impl<I: ParserInput, O, E, F> Parser<I, O, E> for (F, Bnf)
+impl<I: ParserInput, O, E, P> Parser<I, O, E> for (P, Bnf)
 where
-    F: Fn(I) -> ParseResult<I, O, E>,
+    P: Parser<I, O, E>,
 {
     fn parse(&self, input: I) -> ParseResult<I, O, E> {
-        self.0(input)
+        self.0.parse(input)
     }
 
     fn bnf(&self) -> Option<Bnf> {