lisp eval

1 files changed, 59 insertions, 0 deletions

diff --git a/lisp/src/eval.rs b/lisp/src/eval.rs
new file mode 100644
index 0000000..2afe049
--- /dev/null
+++ b/lisp/src/eval.rs
@@ -0,0 +1,59 @@
+use crate::ast::Val;
+
+pub fn eval_f(f: &str, args: &[Val]) -> Val {
+    match f {
+        "quote" if args.len() == 1 => args[0].clone(),
+        _ => Val::Atom("error".to_string()),
+    }
+}
+
+pub fn eval(v: &Val) -> Val {
+    match v {
+        v @ Val::Atom(_) => v.clone(),
+        v @ Val::I64(_) => v.clone(),
+        v @ Val::String(_) => v.clone(),
+        v @ Val::List(vs) => {
+            if vs.is_empty() {
+                return v.clone();
+            }
+            match &vs[0] {
+                Val::Atom(f) => eval_f(&f, &vs[1..]),
+                _ => v.clone(),
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn eval_atom() {
+        assert_eq!(
+            eval(&Val::Atom("x".to_string())),
+            Val::Atom("x".to_string())
+        );
+    }
+    #[test]
+    fn eval_i64() {
+        assert_eq!(eval(&Val::I64(1)), Val::I64(1));
+    }
+    #[test]
+    fn eval_string() {
+        assert_eq!(
+            eval(&Val::String("hello".to_string())),
+            Val::String("hello".to_string())
+        );
+    }
+    #[test]
+    fn eval_quote() {
+        assert_eq!(
+            eval(&Val::List(vec!(
+                Val::Atom("quote".to_string()),
+                Val::Atom("x".to_string())
+            ))),
+            Val::Atom("x".to_string())
+        );
+    }
+}