From fe2eac31d9dbec772796c3ea75be32e9cd01b810 Mon Sep 17 00:00:00 2001
From: Greg Brown <gmb60@cam.ac.uk>
Date: Thu, 7 Jan 2021 12:44:06 +0000
Subject: Add first steps of AutoChomp

---
 chewed/src/error.rs | 4 +++-
 chewed/src/parse.rs | 8 ++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

(limited to 'chewed')

diff --git a/chewed/src/error.rs b/chewed/src/error.rs
index cb2cc4b..420a376 100644
--- a/chewed/src/error.rs
+++ b/chewed/src/error.rs
@@ -11,7 +11,7 @@ impl fmt::Display for TakeError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::BadBranch(got, expected) => {
-                write!(f, "Unexpected character {:?}.", got)?;
+                write!(f, "Unexpected character {:?}. ", got)?;
 
                 if expected.is_empty() {
                     write!(f, "Expected end of input.")
@@ -51,6 +51,8 @@ impl fmt::Display for ParseError {
     }
 }
 
+impl Error for ParseError {}
+
 impl From<TakeError> for ParseError {
     fn from(e: TakeError) -> Self {
         Self::TakeError(e)
diff --git a/chewed/src/parse.rs b/chewed/src/parse.rs
index 0687ea5..f6bbd66 100644
--- a/chewed/src/parse.rs
+++ b/chewed/src/parse.rs
@@ -1,3 +1,5 @@
+use std::iter::Peekable;
+
 use super::error::{ParseError, TakeError};
 
 pub trait Parser: Iterator<Item = char> {
@@ -37,6 +39,12 @@ pub trait Parser: Iterator<Item = char> {
     }
 }
 
+impl<I: Iterator<Item = char>> Parser for Peekable<I> {
+    fn peek(&mut self) -> Option<char> {
+        Peekable::peek(self).copied()
+    }
+}
+
 pub trait Parse: Sized {
     fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError>;
 
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