wip: compiles and runs (not enabled yet)

edn/src/edn_item.rs

@@ -0,0 +1,60 @@
+use crate::*;
+
+fn number (digits: &str) -> usize {
+    let mut value = 0;
+    for c in digits.chars() {
+        value = 10 * value + digit(c);
+    }
+    value
+}
+
+const fn digit (c: char) -> usize {
+    match c { '0' => 0, '1' => 1, '2' => 2, '3' => 3, '4' => 4,
+              '5' => 5, '6' => 6, '7' => 7, '8' => 8, '9' => 9, _ => unreachable!() }
+}
+
+#[derive(Debug)]
+pub enum ParseError {
+    Empty,
+    Unexpected(char),
+    Incomplete
+}
+
+#[derive(Debug, Clone, Default, PartialEq)]
+pub enum Item<T: AsRef<str>> {
+    #[default] Nil,
+    Num(usize),
+    Sym(T),
+    Key(T),
+    Exp(Vec<Item<T>>),
+}
+
+impl Item<String> {
+    pub fn read_all <'a> (mut source: &'a str) -> Result<Vec<Self>, ParseError> {
+        let mut items = vec![];
+        loop {
+            if source.len() == 0 {
+                break
+            }
+            let (remaining, token) = Token::chomp(source)?;
+            match Item::read(token)? { Item::Nil => {}, item => items.push(item) };
+            source = remaining
+        }
+        Ok(items)
+    }
+    pub fn read <'a> (token: Token<'a>) -> Result<Self, ParseError> {
+        use Token::*;
+        Ok(match token {
+            Nil => Item::Nil,
+            Num(chars, index, length) =>
+                Self::Num(number(&chars[index..index+length])),
+            Sym(chars, index, length) =>
+                Self::Sym(chars[index..index+length].to_string()),
+            Key(chars, index, length) =>
+                Self::Key(chars[index..index+length].to_string()),
+            Exp(chars, index, length, 0) =>
+                Self::Exp(Self::read_all(&chars[index+1..(index+length).saturating_sub(1)])?),
+            _ => panic!("unclosed delimiter")
+        })
+    }
+}