noodling on sexp

justfile

@@ -2,5 +2,5 @@ _default:
     just --list
 
 
-test:
+test *args:
-    cargo nextest run
+    cargo nextest run {{args}}

src/parser.rs

@@ -1,4 +1,4 @@
-use crate::{map, seq2};
+use crate::{map, seq2, surrounded_by};
 
 pub type ParseResult<I, O, E> = Result<(O, I), (E, I)>;
 
@@ -24,6 +24,7 @@ pub trait ParserExtension<I, O, E>: Parser<I, O, E> {
     fn then<O2, P: Parser<I, O2, E>>(self, next: P) -> impl Parser<I, (O, O2), E>;
     fn then_ignore<O2, P: Parser<I, O2, E>>(self, next: P) -> impl Parser<I, O, E>;
     fn ignore_then<O2, P: Parser<I, O2, E>>(self, next: P) -> impl Parser<I, O2, E>;
+    fn surrounded_by<O2>(self, surrounding: impl Parser<I, O2, E>) -> impl Parser<I, O, E>;
 }
 
 impl<T, I, O, E> ParserExtension<I, O, E> for T
@@ -51,4 +52,7 @@ where
     fn ignore_then<O2, P: Parser<I, O2, E>>(self, next: P) -> impl Parser<I, O2, E> {
         seq2(self, next).map(|(_, next)| next)
     }
+    fn surrounded_by<O2>(self, surrounding: impl Parser<I, O2, E>) -> impl Parser<I, O, E> {
+        surrounded_by(self, surrounding)
+    }
 }

src/primitives.rs

@@ -49,6 +49,7 @@ pub fn identifier(input: &str) -> ParseResult<&str, String, ()> {
 }
 
 pub fn whitespace(input: &str) -> ParseResult<&str, char, ()> {
+    println!("whitespace: `{input}`");
     match input.chars().next() {
         Some(ch) if ch.is_whitespace() => Ok((ch, &input[1..])),
         _ => Err(((), input)),

src/sequence.rs

@@ -7,6 +7,22 @@ where
     move |input| -> ParseResult<I, O, E> { sequence.parse(input) }
 }
 
+pub fn surrounded_by<I, O1, O2, E>(
+    main: impl Parser<I, O1, E>,
+    surrounding: impl Parser<I, O2, E>,
+) -> impl Parser<I, O1, E> {
+    move |input| {
+        println!("surrounded_by");
+        let (_result1, rest1) = surrounding.parse(input)?;
+        println!("A");
+        let (result2, rest2) = main.parse(rest1)?;
+        println!("B");
+        let (_result3, rest3) = surrounding.parse(rest2)?;
+        println!("C");
+        Ok((result2, rest3))
+    }
+}
+
 pub fn seq2<I, O1, O2, E>(
     first: impl Parser<I, O1, E>,
     second: impl Parser<I, O2, E>,
@@ -32,3 +48,22 @@ where
         })
     }
 }
+
+impl<P1, P2, P3, I, O1, O2, O3, E> Sequence<I, (O1, O2, O3), E> for (P1, P2, P3)
+where
+    P1: Parser<I, O1, E>,
+    P2: Parser<I, O2, E>,
+    P3: Parser<I, O3, E>,
+{
+    fn parse(&self, input: I) -> ParseResult<I, (O1, O2, O3), E> {
+        let p1 = &self.0;
+        let p2 = &self.1;
+        let p3 = &self.2;
+
+        let (result1, rest1) = p1.parse(input)?;
+        let (result2, rest2) = p2.parse(rest1)?;
+        let (result3, rest3) = p3.parse(rest2)?;
+
+        Ok(((result1, result2, result3), rest3))
+    }
+}

src/test/mod.rs

@@ -67,4 +67,9 @@ fn test_repeated() {
     let output = parser.parse("bongo bongo     bongo           bongo");
     let output = output.unwrap();
     assert_eq!(output.0, vec!["bongo", "bongo", "bongo", "bongo"]);
+
+    let bongos = repeated(literal("bongo"));
+    let output = bongos.parse("tra la la").unwrap();
+    assert_eq!(output.0.len(), 0);
+    assert_eq!(output.1, "tra la la");
 }

src/test/sexp.rs

@@ -48,6 +48,7 @@ fn test_parse_atom() {
 }
 
 fn parse_expr(input: &str) -> ParseResult<&str, Expr, ()> {
+    println!("parse_expr: {input}");
     choice((parse_list, parse_atom.map(Expr::Atom))).parse(input)
 }
 
@@ -60,9 +61,17 @@ fn parse_list(input: &str) -> ParseResult<&str, Expr, ()> {
         )
         .then_ignore(literal_char(')'))
         .map(Expr::List)
+        .surrounded_by(repeated(whitespace))
         .parse(input)
 }
 
+#[test]
+fn test_parse_list() {
+    let output = parse_list.parse("\n(1 2 (1 2) 9999 3)").unwrap();
+    assert_eq!(output.1, "");
+
+}
+
 #[test]
 fn test_parse_sexp() {
     let output = parse_expr("(add 1 2)").unwrap();