From fac291446581b1dad939545bafd6da349c4dfd40 Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Sat, 10 Apr 2021 10:23:35 +0530
Subject: add `for` primitive

---
 src/grid.rs         |  2 +-
 src/lisp/eval.rs    | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lisp/prelude.rs | 18 +++++++++++++++
 3 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/src/grid.rs b/src/grid.rs
index 029a196..ed1dd83 100644
--- a/src/grid.rs
+++ b/src/grid.rs
@@ -81,7 +81,7 @@ impl Grid {
             }
             GridKind::Isometric => {
                 canvas.set_clip_rect(Some(rect!(x, y, width * cs, height * cs)));
-                for i in (0..2 * height + width).step_by(4) {
+                for i in (0..2 * height + width).step_by(2) {
                     let begin = ((i * cs) as i32, 0i32);
                     let end = (0i32, (i * cs) as i32 / 2);
                     canvas
diff --git a/src/lisp/eval.rs b/src/lisp/eval.rs
index 329b6ab..0cf267c 100644
--- a/src/lisp/eval.rs
+++ b/src/lisp/eval.rs
@@ -41,6 +41,7 @@ where
                         "lambda" => create_lambda(&li[1..]),
                         "if" => self.eval_if(&li[1..]),
                         "cond" => self.eval_cond(&li[1..]),
+                        "for" => self.eval_for(&li[1..]),
                         "quote" => Ok(apply_quote(&li[1])),
                         "let" => self.eval_let(&li[1..]),
                         _ => {
@@ -214,6 +215,55 @@ where
         }
     }
 
+    pub fn eval_for(&mut self, args: &[LispExpr]) -> Result<LispExpr, LispError> {
+        let arity = Arity::Exact(2);
+        let valid_binding_stmt = |expr: &LispExpr| 
+            matches!(
+                expr,
+                LispExpr::List(v) 
+                if v.len() == 2 
+                && matches!(v[0], LispExpr::Ident(_)));
+
+        if !arity.check(args) {
+            Err(arity.to_error())
+        } else {
+            let nested_env = Environment::new();
+            self.app.lisp_env.push(nested_env);
+            match args {
+                [binding, body] => {
+                    if valid_binding_stmt(binding) {
+                        let binding = binding.unwrap_list();
+                        let binding_name = binding[0].unwrap_ident();
+                        let binding_ls = self.eval(&binding[1])?;
+                        if matches!(binding_ls, LispExpr::List(_)) {
+                            let binding_ls = binding_ls.unwrap_list();
+                            let mut result = vec![];
+                            for bind_val in binding_ls.iter() {
+                                let value = self.eval(&bind_val)?;
+                                if let Some(env) = self.app.lisp_env.last_mut() {
+                                    env.insert(binding_name.clone(), value);
+                                }
+                                result.push(self.eval(body)?);
+                            }
+                            self.app.lisp_env.pop();
+                            Ok(LispExpr::List(result))
+                        } else {
+                            error!("invalid binding form");
+                            Err(EvalError::BadForm.into())
+                        }
+                    } else {
+                        error!("invalid binding form");
+                        Err(EvalError::BadForm.into())
+                    }
+                }
+                _ => {
+                    error!("invalid for loop args");
+                    Err(EvalError::BadForm.into()) 
+                },
+            }
+        }
+    }
+
     pub fn eval_let(&mut self, args: &[LispExpr]) -> Result<LispExpr, LispError> {
         let arity = Arity::Exact(2);
         let valid_binding_stmt =
@@ -326,7 +376,9 @@ mod tests {
         let mut app = AppState::init(100, 100, &sdl_context, &ttf_context, None, None).unwrap();
         eval_arithmetic(&mut app);
         eval_logical(&mut app);
+        eval_looping(&mut app);
         eval_quote(&mut app);
+        eval_std_tests(&mut app);
     }
 
     fn eval_arithmetic(app: &mut AppState) {
@@ -380,4 +432,15 @@ mod tests {
         assert!(!run("(not #t)", app).cast_bool());
         assert_eq!(run("(not #f)", app), run("(not (not #t))", app));
     }
+
+    fn eval_looping(app: &mut AppState) {
+        assert_eq!(
+            run("(for (i '(1 2 3)) (+ i 2))", app),
+            run("(map (lambda (x) (+ x 2)) '(1 2 3))", app)
+        );
+    }
+
+    fn eval_std_tests(app: &mut AppState) {
+        crate::utils::load_script("src/lisp/test.lisp", app).unwrap();
+    }
 }
diff --git a/src/lisp/prelude.rs b/src/lisp/prelude.rs
index f5ff13a..e24ade5 100644
--- a/src/lisp/prelude.rs
+++ b/src/lisp/prelude.rs
@@ -437,5 +437,23 @@ pub fn new_env() -> Result<Environment, LispError> {
         }
     });
 
+    primitive!(env, Arity::Exact(2), "range", |args, _| {
+        if type_match!(
+            args,
+            0 => LispExpr::Number(LispNumber::Integer(_)),
+            1 => LispExpr::Number(LispNumber::Integer(_)))
+        {
+            let lower = args[0].unwrap_number().unwrap_integer();
+            let upper = args[1].unwrap_number().unwrap_integer();
+            Ok(LispExpr::List(
+                (lower..upper)
+                    .map(|i| LispExpr::Number(LispNumber::Integer(i)))
+                    .collect::<Vec<_>>(),
+            ))
+        } else {
+            Err(EvalError::TypeMismatch.into())
+        }
+    });
+
     Ok(env)
 }
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