From f94f22a3d0aeff98cc9169c94b683aa139e9c81c Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Sat, 27 Mar 2021 13:16:25 +0530
Subject: implement char literals

---
 src/lisp/lex.rs | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

(limited to 'src/lisp/lex.rs')

diff --git a/src/lisp/lex.rs b/src/lisp/lex.rs
index b307e80..1a34e53 100644
--- a/src/lisp/lex.rs
+++ b/src/lisp/lex.rs
@@ -8,7 +8,7 @@ pub enum Token<'a> {
     RightParen,
     Float(&'a str),
     Integer(&'a str),
-    // Char(&'a str),
+    Char(&'a str),
     String(&'a str),
     Name(&'a str),
     // Keyword(&'a str),
@@ -26,7 +26,7 @@ impl<'a> Token<'a> {
             Token::RightParen => ")",
             Token::Float(_) => "float",
             Token::Integer(_) => "integer",
-            // Token::Char(_)    => "char",
+            Token::Char(_) => "char",
             Token::String(_) => "string",
             Token::Name(_) => "name",
             // Token::Keyword(_) => "keyword",
@@ -46,7 +46,7 @@ impl<'a> fmt::Display for Token<'a> {
             Token::RightParen => write!(f, ")"),
             Token::Float(_) => write!(f, "float"),
             Token::Integer(_) => write!(f, "integer"),
-            // Token::Char(_) => write!(f, "char"),
+            Token::Char(_) => write!(f, "char"),
             Token::String(_) => write!(f, "string"),
             Token::Name(_) => write!(f, "name"),
             // Token::Keyword(_) => write!(f, "keyword"),
@@ -122,7 +122,10 @@ impl<'a> Lexer<'a> {
                     Some((_, '@')) => Ok((2, Token::CommaAt)),
                     _ => Ok((1, Token::Comma)),
                 },
-                '#' => parse_name(&self.input[ind..]),
+                '#' => match chars.next() {
+                    Some((_, '\\')) => parse_char(&self.input[ind..]),
+                    _ => parse_name(&self.input[ind..]),
+                },
                 '-' | '0'..='9' => parse_number(&self.input[ind..]),
                 '"' => parse_string(&self.input[ind..]),
                 ';' => {
@@ -254,6 +257,12 @@ fn parse_name<'a>(input: &'a str) -> Result<(usize, Token<'a>), ParseErrorKind>
     return Ok((input.len(), Token::Name(input)));
 }
 
+fn parse_char<'a>(input: &'a str) -> Result<(usize, Token<'a>), ParseErrorKind> {
+    // first two chars of input are '#' and '\'
+    let chr = &input[..3];
+    return Ok((chr.len(), Token::Char(chr)));
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -282,6 +291,14 @@ mod tests {
         assert_eq!(parsed.1, Token::String(r#""hello there""#));
     }
 
+    #[test]
+    fn char_parsing() {
+        let input = r##"#\a"##;
+        let parsed = parse_char(input).unwrap();
+        assert_eq!(parsed.0, 3);
+        assert_eq!(parsed.1, Token::Char(r##"#\a"##));
+    }
+
     #[test]
     fn integer_parsing() {
         let input = "12345";
-- 
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