Cargo.lock

@@ -1625,6 +1625,14 @@ dependencies = [
  "minimal-lexical",
 ]
 
+[[package]]
+name = "nom-training"
+version = "0.1.0"
+dependencies = [
+ "cool_asserts",
+ "nom",
+]
+
 [[package]]
 name = "num-integer"
 version = "0.1.45"

Cargo.toml

@@ -18,4 +18,5 @@ members = [
     "memorycache",
     "screenplay",
     "sgf",
+    "nom-training",
 ]

nom-training/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "nom-training"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+nom = { version = "7" }
+cool_asserts = { version = "*" }

nom-training/src/lib.rs

@@ -0,0 +1,122 @@
+// Write two separate parser functions
+// One function returns `impl Parser<>`
+// The other function returns `FnMut(I) -> IResult<I, ...`
+// Test each with the `map` function and the `parse` function
+use nom::{character::complete::digit1, error::ParseError, IResult, Parser};
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+struct Container(i32);
+
+#[allow(dead_code)]
+fn parse_container_a<'a, E: ParseError<&'a str>>(
+    mut parser: impl Parser<&'a str, i32, E>,
+) -> impl FnMut(&'a str) -> IResult<&'a str, Container, E> {
+    move |input| {
+        let (input, value) = parser.parse(input)?;
+        Ok((input, Container(value)))
+    }
+}
+
+/*
+// This form doesn't work. It is not possible in this case to get the ownership
+// declarations correct on parser. The reason I would want to do this is for more
+// concise representation of parse_container_a. It probably fails because map consumes
+// the parser.
+fn parse_container_b<'a, E: ParseError<&'a str>, P>(
+    mut parser: P,
+) -> impl Parser<&'a str, Container, E>
+where
+    P: Parser<&'a str, i32, E>,
+{
+    move |input| parser.map(|val| Container(val)).parse(input)
+}
+*/
+
+#[allow(dead_code)]
+fn parse_container_c<'a, E: ParseError<&'a str>>(
+    parser: impl Parser<&'a str, i32, E>,
+) -> impl Parser<&'a str, Container, E> {
+    parser.map(|val| Container(val))
+}
+
+/*
+// This form also doesn't work, for the same reason as parse_container_b doesn't work.
+fn parse_container_d<'a, E: ParseError<&'a str>>(
+    parser: impl Parser<&'a str, i32, E>,
+) -> impl FnMut(&'a str) -> IResult<&'a str, Container, E> {
+    |input| parser.map(|val| Container(val)).parse(input)
+}
+*/
+
+// If I really want to do forms b and d, this works. I do the parser combination before
+// creating the resulting function.
+#[allow(dead_code)]
+fn parse_container_e<'a, E: ParseError<&'a str>>(
+    parser: impl Parser<&'a str, i32, E>,
+) -> impl Parser<&'a str, Container, E> {
+    let mut parser = parser.map(|val| Container(val));
+
+    move |input| parser.parse(input)
+}
+
+#[allow(dead_code)]
+fn parse_number_a<'a, E: ParseError<&'a str>>() -> impl FnMut(&'a str) -> IResult<&'a str, i32, E> {
+    parse_number
+}
+
+#[allow(dead_code)]
+fn parse_number_b<'a, E: ParseError<&'a str>>() -> impl Parser<&'a str, i32, E> {
+    parse_number
+}
+
+#[allow(dead_code)]
+fn parse_number<'a, E: ParseError<&'a str>>(input: &'a str) -> IResult<&'a str, i32, E> {
+    let (input, val) = digit1(input)?;
+    Ok((input, val.parse::<i32>().unwrap()))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use cool_asserts::assert_matches;
+
+    const DATA: &'static str = "15";
+
+    #[test]
+    fn function() {
+        let resp = parse_number_a::<nom::error::VerboseError<&str>>()
+            .map(|val| Container(val))
+            .parse(DATA);
+        assert_matches!(resp, Ok((_, content)) =>
+                assert_eq!(content, Container(15))
+        );
+    }
+
+    #[test]
+    fn parser() {
+        let resp = parse_number_b::<nom::error::VerboseError<&str>>()
+            .map(|val| Container(val))
+            .parse(DATA);
+        assert_matches!(resp, Ok((_, content)) =>
+                assert_eq!(content, Container(15))
+        );
+    }
+
+    #[test]
+    fn parser_composition_a() {
+        let resp =
+            parse_container_a::<nom::error::VerboseError<&str>>(parse_number_a()).parse(DATA);
+        assert_matches!(resp, Ok((_, content)) =>
+                assert_eq!(content, Container(15))
+        );
+    }
+
+    #[test]
+    fn parser_composition_c() {
+        let resp =
+            parse_container_c::<nom::error::VerboseError<&str>>(parse_number_b()).parse(DATA);
+        assert_matches!(resp, Ok((_, content)) =>
+                assert_eq!(content, Container(15))
+        );
+    }
+}