feat(prelude): add progn

src/bin/demo.rs

@@ -15,6 +15,7 @@ fn main() {
         "(let '((a . (vec3 1 2 3)) (b . (vec3 4 5 6))) (vec3-dot (vec3-norm (vec3-add a b)) a))",
         "(defun do-n-times (f n) (if (= n 0) '() (cons (f) (do-n-times f (- n 1)))))",
         "(do-n-times (lambda () (print 'hello)) 5)",
+        "(progn (print 'hello) (print 'world))",
     ];
 
     let environment = Environment::default();

src/lisp/eval.rs

@@ -103,7 +103,7 @@ pub fn eval(env: &Environment, expr: Expression) -> Result<Expression, EvalError
             a => Err(EvalError::NotAFunction(a)),
         },
         Expression::Quote(e) => Ok(*e),
-        Expression::Symbol(s) => eval(env, env.get(&s).ok_or(EvalError::SymbolNotBound(s))?),
+        Expression::Symbol(s) => env.get(&s).ok_or(EvalError::SymbolNotBound(s)),
         x => Ok(x),
     }
 }

src/lisp/prelude.rs

@@ -245,6 +245,16 @@ pub fn prelude_eval(env: &Environment, expr: Expression) -> Result<Expression, E
     eval(env, eval(env, e)?)
 }
 
+pub fn prelude_progn(env: &Environment, expr: Expression) -> Result<Expression, EvalError> {
+    let mut result = Expression::Nil;
+
+    for e in CellIterator::new(expr) {
+        result = eval(env, e?)?;
+    }
+
+    Ok(result)
+}
+
 pub fn mk_prelude(layer: &mut EnvironmentLayer) {
     layer.set("+".to_string(), Expression::Function(prelude_add));
     layer.set("-".to_string(), Expression::Function(prelude_sub));
@@ -265,4 +275,5 @@ pub fn mk_prelude(layer: &mut EnvironmentLayer) {
     layer.set("car".to_string(), Expression::Function(prelude_car));
     layer.set("cdr".to_string(), Expression::Function(prelude_cdr));
     layer.set("eval".to_string(), Expression::Function(prelude_eval));
+    layer.set("progn".to_string(), Expression::Function(prelude_progn));
 }