Pass input out

src/choice.rs

@@ -1,21 +1,19 @@
 use crate::Parser;
 
-pub fn choice<'a, I, O, E>(parsers: &'a [&'a dyn Parser<I, O, E>]) -> impl Parser<I, O, E> + 'a
-where
-    I: Clone,
-{
-    move |input: I| {
+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;
 
         for parser in parsers.iter() {
-            match parser.parse(input.clone()) {
+            match parser.parse(input) {
                 Ok(res) => return Ok(res),
-                Err(e) => {
+                Err((e, rest)) => {
                     err = Some(e);
+                    input = rest;
                 }
             }
         }
-        Err(err.unwrap())
+        Err((err.unwrap(), input))
     }
 }

src/combinators.rs

@@ -3,16 +3,23 @@ use crate::Parser;
 pub fn repeated<P, I, O, E>(parser: P) -> impl Parser<I, Vec<O>, E>
 where
     P: Parser<I, O, E>,
-    I: Copy,
 {
     move |input: I| {
         let mut acc = input;
         let mut results = vec![];
 
-        while let Ok((item, rest)) = parser.parse(acc) {
+        loop {
+            match parser.parse(acc) {
+                Ok((item, rest)) => {
                     results.push(item);
                     acc = rest;
                 }
+                Err((_err, rest)) => {
+                    acc = rest;
+                    break;
+                }
+            }
+        }
         Ok((results, acc))
     }
 }

src/lib.rs

@@ -11,7 +11,7 @@ pub use map::*;
 pub use primitives::*;
 pub use sequence::*;
 
-type ParseResult<I, O, E> = Result<(O, I), E>;
+type ParseResult<I, O, E> = Result<(O, I), (E, I)>;
 
 pub trait Parser<I, O, E> {
     fn parse(&self, input: I) -> ParseResult<I, O, E>;
@@ -51,7 +51,7 @@ mod tests {
         let a = literal("bongo");
         let b = literal("sucy");
         let c = literal("ara");
-        let inputs = [&a as &dyn Parser<&str, &str, &str>, &b, &c];
+        let inputs = [&a as &dyn Parser<&str, &str, ()>, &b, &c];
         let parser = choice(&inputs);
 
         let output = parser.parse("ara hajimete").unwrap();

src/primitives.rs

@@ -1,16 +1,16 @@
 use crate::{ParseResult, Parser};
 
-pub fn literal(expected: &'static str) -> impl Fn(&str) -> ParseResult<&str, &str, &str> {
+pub fn literal(expected: &'static str) -> impl Fn(&str) -> ParseResult<&str, &str, ()> {
     move |input| match input.get(0..expected.len()) {
         Some(next) if next == expected => Ok((next, &input[expected.len()..])),
-        _ => Err(input),
+        _ => Err(((), input)),
     }
 }
 
-pub fn literal_char<'a>(expected: char) -> impl Parser<&'a str, char, &'a str> {
+pub fn literal_char<'a>(expected: char) -> impl Parser<&'a str, char, ()> {
     move |input: &'a str| match input.chars().next() {
         Some(ch) if ch == expected => Ok((expected, &input[ch.len_utf8()..])),
-        _ => Err(input),
+        _ => Err(((), input)),
     }
 }