More combinators, s expression test

src/choice.rs

@@ -1,19 +1,49 @@
-use crate::Parser;
+use crate::{ParseResult, Parser};
 
-pub fn choice<'a, I, O, E>(parsers: &'a [&'a dyn Parser<I, O, E>]) -> impl Parser<I, O, E> + 'a {
-    move |mut input: I| {
-        //TODO need a more principled way to return an error when no choices work
-        let mut err = None;
+pub trait Choice<I, O, E> {
+    fn parse_choice(&self, input: I) -> Result<(O, I), (E, I)>;
+}
 
-        for parser in parsers.iter() {
-            match parser.parse(input) {
-                Ok(res) => return Ok(res),
-                Err((e, rest)) => {
-                    err = Some(e);
-                    input = rest;
-                }
+pub fn choice<C: Choice<I, O, E>, I, O, E>(choices: C) -> impl Parser<I, O, E> {
+    move |input| choices.parse_choice(input)
+}
+
+fn choice_loop<'a, I, O, E>(
+    mut input: I,
+    parsers: &'a [&'a dyn Parser<I, O, E>],
+) -> ParseResult<I, O, E> {
+    //TODO need a more principled way to return an error when no choices work
+    let mut err = None;
+
+    for parser in parsers.iter() {
+        match parser.parse(input) {
+            Ok(res) => return Ok(res),
+            Err((e, rest)) => {
+                err = Some(e);
+                input = rest;
             }
         }
-        Err((err.unwrap(), input))
+    }
+    Err((err.unwrap(), input))
+}
+
+impl<P1, P2, I, O, E> Choice<I, O, E> for (P1, P2)
+where
+    P1: Parser<I, O, E>,
+    P2: Parser<I, O, E>,
+{
+    fn parse_choice(&self, input: I) -> Result<(O, I), (E, I)> {
+        choice_loop(input, &[&self.0, &self.1])
+    }
+}
+
+impl<P1, P2, P3, I, O, E> Choice<I, O, E> for (P1, P2, P3)
+where
+    P1: Parser<I, O, E>,
+    P2: Parser<I, O, E>,
+    P3: Parser<I, O, E>,
+{
+    fn parse_choice(&self, input: I) -> Result<(O, I), (E, I)> {
+        choice_loop(input, &[&self.0, &self.1, &self.2])
     }
 }

src/lib.rs

@@ -6,85 +6,12 @@ mod parser;
 mod primitives;
 mod sequence;
 
+#[cfg(test)]
+mod test;
+
 pub use choice::*;
 pub use combinators::*;
 pub use map::*;
 pub use parser::{ParseResult, Parser, ParserExtension};
 pub use primitives::*;
 pub use sequence::*;
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn parsing() {
-        let (parsed, rest) = literal("a")("a yolo").unwrap();
-        assert_eq!(parsed, "a");
-        assert_eq!(rest, " yolo");
-    }
-
-    #[test]
-    fn test_sequence() {
-        let parser = seq2(literal("bongo"), seq2(literal(" "), literal("jonzzz")));
-        let output = parser.parse("bongo jonzzz").unwrap();
-        assert_eq!(output.0 .0, "bongo");
-        assert_eq!(output.0 .1, (" ", "jonzzz"));
-        assert_eq!(output.1, "");
-    }
-
-    #[test]
-    fn test_choice() {
-        let a = literal("bongo");
-        let b = literal("sucy");
-        let c = literal("ara");
-        let inputs = [&a as &dyn Parser<&str, &str, ()>, &b, &c];
-        let parser = choice(&inputs);
-
-        let output = parser.parse("ara hajimete").unwrap();
-        assert_eq!(("ara", " hajimete"), output);
-    }
-
-    #[test]
-    fn test_map() {
-        let parser =
-            seq2(literal("a"), literal("b")).map(|(a, _b): (&str, &str)| (a.to_uppercase(), 59));
-        let output = parser.parse("abcd").unwrap();
-        assert_eq!((("A".to_owned(), 59), "cd"), output);
-
-        let spaces = repeated(literal_char(' ')).at_least(1);
-        let parser = seq2(literal("lute"), spaces).to(500);
-        assert_eq!(parser.parse("lute    "), Ok((500, "")));
-        assert_eq!(parser.parse("lute"), Err(((), "")));
-    }
-
-    #[test]
-    fn test_combinators() {
-        let parser = repeated(literal_char('a')).to(10).then(literal_char('b'));
-        let output = parser.parse("aaaaaaaabcd").unwrap();
-        assert_eq! {((10, 'b'), "cd"), output};
-    }
-
-    #[test]
-    fn test_optional() {
-        let parser = seq2(
-            optional(literal("alpha")),
-            seq2(repeated(literal(" ")), literal("beta")),
-        );
-
-        let output1 = parser.parse("   beta").unwrap();
-        assert_eq!(output1.0 .0, None);
-        let output2 = parser.parse("alpha   beta").unwrap();
-        assert_eq!(output2.0 .0, Some("alpha"));
-    }
-
-    #[test]
-    fn test_repeated() {
-        let spaces = repeated(literal_char(' ')).at_least(1);
-        let bongo = literal("bongo");
-        let parser = repeated(bongo).separated_by(map(spaces, |_| ()));
-        let output = parser.parse("bongo bongo     bongo           bongo");
-        let output = output.unwrap();
-        assert_eq!(output.0, vec!["bongo", "bongo", "bongo", "bongo"]);
-    }
-}

src/primitives.rs

@@ -14,6 +14,40 @@ pub fn literal_char<'a>(expected: char) -> impl Parser<&'a str, char, ()> {
     }
 }
 
+pub fn one_of<'a>(items: &'static str) -> impl Parser<&'a str, char, ()> {
+    move |input: &'a str| {
+        if let Some(ch) = input.chars().next() {
+            if items.contains(ch) {
+                let (_first, rest) = input.split_at(1);
+                return Ok((ch, rest));
+            }
+        }
+        Err(((), input))
+    }
+}
+
+/// Parses a standard identifier in a programming language
+pub fn identifier(input: &str) -> ParseResult<&str, String, &str> {
+    let mut chars = input.chars();
+    let mut buf = String::new();
+
+    match chars.next() {
+        Some(ch) if ch.is_alphabetic() => buf.push(ch),
+        _ => return Err((input, input)),
+    }
+
+    for next in chars {
+        if next.is_alphanumeric() {
+            buf.push(next);
+        } else {
+            break;
+        }
+    }
+
+    let next_index = buf.len();
+    Ok((buf, &input[next_index..]))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/test/mod.rs

@@ -0,0 +1,70 @@
+mod sexp;
+
+use super::*;
+
+#[test]
+fn parsing() {
+    let (parsed, rest) = literal("a")("a yolo").unwrap();
+    assert_eq!(parsed, "a");
+    assert_eq!(rest, " yolo");
+}
+
+#[test]
+fn test_sequence() {
+    let parser = seq2(literal("bongo"), seq2(literal(" "), literal("jonzzz")));
+    let output = parser.parse("bongo jonzzz").unwrap();
+    assert_eq!(output.0 .0, "bongo");
+    assert_eq!(output.0 .1, (" ", "jonzzz"));
+    assert_eq!(output.1, "");
+}
+
+#[test]
+fn test_choice() {
+    let parser = choice((literal("bongo"), literal("sucy"), literal("ara")));
+
+    let output = parser.parse("ara hajimete").unwrap();
+    assert_eq!(("ara", " hajimete"), output);
+}
+
+#[test]
+fn test_map() {
+    let parser =
+        seq2(literal("a"), literal("b")).map(|(a, _b): (&str, &str)| (a.to_uppercase(), 59));
+    let output = parser.parse("abcd").unwrap();
+    assert_eq!((("A".to_owned(), 59), "cd"), output);
+
+    let spaces = repeated(literal_char(' ')).at_least(1);
+    let parser = seq2(literal("lute"), spaces).to(500);
+    assert_eq!(parser.parse("lute    "), Ok((500, "")));
+    assert_eq!(parser.parse("lute"), Err(((), "")));
+}
+
+#[test]
+fn test_combinators() {
+    let parser = repeated(literal_char('a')).to(10).then(literal_char('b'));
+    let output = parser.parse("aaaaaaaabcd").unwrap();
+    assert_eq! {((10, 'b'), "cd"), output};
+}
+
+#[test]
+fn test_optional() {
+    let parser = seq2(
+        optional(literal("alpha")),
+        seq2(repeated(literal(" ")), literal("beta")),
+    );
+
+    let output1 = parser.parse("   beta").unwrap();
+    assert_eq!(output1.0 .0, None);
+    let output2 = parser.parse("alpha   beta").unwrap();
+    assert_eq!(output2.0 .0, Some("alpha"));
+}
+
+#[test]
+fn test_repeated() {
+    let spaces = repeated(literal_char(' ')).at_least(1);
+    let bongo = literal("bongo");
+    let parser = repeated(bongo).separated_by(map(spaces, |_| ()));
+    let output = parser.parse("bongo bongo     bongo           bongo");
+    let output = output.unwrap();
+    assert_eq!(output.0, vec!["bongo", "bongo", "bongo", "bongo"]);
+}

src/test/sexp.rs

@@ -0,0 +1,34 @@
+use crate::*;
+
+#[derive(Debug, PartialEq)]
+enum Expr {
+    Atom(Atom),
+    List(Vec<Expr>),
+    Quote(Vec<Expr>),
+}
+
+#[derive(Clone, Debug, PartialEq)]
+enum Atom {
+    Num(i64),
+    Str(String),
+    Bool(bool),
+    Symbol(String),
+}
+
+#[test]
+fn parse_sexp() {
+    let parse_bool = choice((
+        literal("#t").to(Atom::Bool(true)),
+        literal("#f").to(Atom::Bool(false)),
+    ));
+
+    let parse_symbol = identifier;
+    let parse_number = repeated(one_of("1234567890"))
+        .at_least(1)
+        .map(|n| Atom::Num(n.iter().collect::<String>().parse::<i64>().unwrap()));
+
+    let parser = choice((parse_bool, parse_number));
+
+    let output = parser.parse("#t").unwrap();
+    assert_eq!(output.0, Atom::Bool(true));
+}