Map

src/lib.rs

@@ -1,9 +1,11 @@
 #![allow(dead_code)] //TODO eventually turn this off
 mod choice;
+mod map;
 mod primitives;
 mod sequence;
 
 pub use choice::*;
+pub use map::*;
 pub use primitives::*;
 pub use sequence::*;
 
@@ -53,4 +55,14 @@ mod tests {
         let output = parser.parse("ara hajimete").unwrap();
         assert_eq!(("ara", " hajimete"), output);
     }
+
+    #[test]
+    fn test_map() {
+        let parser = map(
+            sequence(literal("a"), literal("b")),
+            |(_a, _b): (&str, &str)| 59,
+        );
+        let output = parser.parse("abcd").unwrap();
+        assert_eq!((59, "cd"), output);
+    }
 }

src/map.rs

@@ -0,0 +1,13 @@
+use crate::Parser;
+
+pub fn map<P, F, I, O1, O2, E>(parser: P, map_fn: F) -> impl Parser<I, O2, E>
+where
+    P: Parser<I, O1, E>,
+    F: Fn(O1) -> O2,
+{
+    move |input| {
+        parser
+            .parse(input)
+            .map(|(result, rest)| (map_fn(result), rest))
+    }
+}