Speed sketch beginnings of a Rust implementation of new stripped-down Scheme-like Kraken

kr/src/ast.rs

@@ -0,0 +1,37 @@
+use std::rc::Rc;
+
+#[derive(Debug)]
+pub enum Form {
+    Int(i32),
+    Symbol(String),
+    Pair(Rc<Form>,Rc<Form>),
+    PrimComb(String, fn(Rc<Form>, Rc<Form>) -> Rc<Form>),
+    Nil,
+}
+impl Form {
+    pub fn int(&self) -> Option<i32> {
+        match self {
+            Form::Int(i) => Some(*i),
+            _ => None,
+        }
+    }
+    pub fn sym(&self) -> Option<&str> {
+        match self {
+            Form::Symbol(s) => Some(s),
+            _ => None,
+        }
+    }
+    pub fn car(&self) -> Option<Rc<Form>> {
+        match self {
+            Form::Pair(car, cdr) => Some(Rc::clone(car)),
+            _ => None,
+        }
+    }
+    pub fn cdr(&self) -> Option<Rc<Form>> {
+        match self {
+            Form::Pair(car, cdr) => Some(Rc::clone(cdr)),
+            _ => None,
+        }
+    }
+}
+