From d861d91397e532667ebb718370d965a0b1212ac3 Mon Sep 17 00:00:00 2001
From: Nathan Braswell <nathan@braswell.email>
Date: Wed, 8 Feb 2023 01:54:53 -0500
Subject: [PATCH] Fix ', add if and = along with bools

---
 kr/src/ast.rs          | 14 +++++++++++---
 kr/src/grammar.lalrpop |  8 ++++----
 kr/src/main.rs         | 28 ++++++++++++++++++++++++----
 3 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/kr/src/ast.rs b/kr/src/ast.rs
index 386cd14..a18bffb 100644
--- a/kr/src/ast.rs
+++ b/kr/src/ast.rs
@@ -1,15 +1,23 @@
 use std::rc::Rc;
 
-#[derive(Debug)]
+#[derive(Debug, Eq, PartialEq)]
 pub enum Form {
+    Nil,
     Int(i32),
+    Bool(bool),
     Symbol(String),
     Pair(Rc<Form>,Rc<Form>),
-    DeriComb { se: Rc<Form>, de: Option<String>, params: Rc<Form>, body: Rc<Form> },
     PrimComb(String, fn(Rc<Form>, Rc<Form>) -> Rc<Form>),
-    Nil,
+    DeriComb { se: Rc<Form>, de: Option<String>, params: Rc<Form>, body: Rc<Form> },
 }
 impl Form {
+    pub fn truthy(&self) -> bool {
+        match self {
+            Form::Bool(b) => *b,
+            Form::Nil     => false,
+            _             => true,
+        }
+    }
     pub fn int(&self) -> Option<i32> {
         match self {
             Form::Int(i) => Some(*i),
diff --git a/kr/src/grammar.lalrpop b/kr/src/grammar.lalrpop
index 65b7f4b..6a429f2 100644
--- a/kr/src/grammar.lalrpop
+++ b/kr/src/grammar.lalrpop
@@ -8,7 +8,7 @@ pub Term: Form = {
     NUM => Form::Int(i32::from_str(<>).unwrap()),
     SYM => Form::Symbol(<>.to_owned()),
 	"(" <ListInside?> ")" => <>.unwrap_or(Form::Nil),
-	"'" <Term> => Form::Pair(Rc::new(Form::Symbol("quote".to_owned())), Rc::new(<>)),
+	"'" <Term> => Form::Pair(Rc::new(Form::Symbol("quote".to_owned())), Rc::new(Form::Pair(Rc::new(<>), Rc::new(Form::Nil)))),
 };
 ListInside: Form = {
 	<Term> => Form::Pair(Rc::new(<>), Rc::new(Form::Nil)),
@@ -20,8 +20,8 @@ match {
     ")",
     ".",
     "'",
-    r"[0-9]+"                  => NUM,
-	r"[a-zA-Z+*/_-][\w+*/_-]*" => SYM,
-	r"(;[^\n]*\n)|\s+"         => { }
+    r"[0-9]+"                    => NUM,
+	r"[a-zA-Z+*/_=-][\w+*/=_-]*" => SYM,
+	r"(;[^\n]*\n)|\s+"           => { }
 }
 
diff --git a/kr/src/main.rs b/kr/src/main.rs
index 341bf33..8e7367b 100644
--- a/kr/src/main.rs
+++ b/kr/src/main.rs
@@ -105,8 +105,20 @@ fn main() {
 
             Rc::new(Form::DeriComb { se: e, de, params, body })
         }))),
-        ("quote", Rc::new(Form::PrimComb("quote".to_owned(), |e, p| {
-            p
+        ("=", Rc::new(Form::PrimComb("=".to_owned(), |e, p| {
+            let a = eval(Rc::clone(&e), p.car().unwrap());
+            let b = eval(e, p.cdr().unwrap().car().unwrap());
+            Rc::new(Form::Bool(a == b))
+        }))),
+        ("if", Rc::new(Form::PrimComb("if".to_owned(), |e, p| {
+            if eval(Rc::clone(&e), p.car().unwrap()).truthy() {
+                eval(e, p.cdr().unwrap().car().unwrap())
+            } else if let Some(els) = p.cdr().unwrap().cdr().and_then(|x| x.car()) {
+                eval(e, els)
+            } else {
+                // should we really allow this? (2 arg if with no else)
+                Rc::new(Form::Nil)
+            }
         }))),
         ("+", Rc::new(Form::PrimComb("+".to_owned(), |e, p| {
             let a = eval(Rc::clone(&e), p.car().unwrap()).int().unwrap();
@@ -124,9 +136,17 @@ fn main() {
         ("cdr", Rc::new(Form::PrimComb("cdr".to_owned(), |e, p| {
             eval(Rc::clone(&e), p.car().unwrap()).cdr().unwrap()
         }))),
+        ("quote", Rc::new(Form::PrimComb("quote".to_owned(), |e, p| {
+            p.car().unwrap()
+        }))),
     ]);
     //let input = "(+ 2 (car (cons 4 '(1 2))))";
-    let input = "((vau d p (+ (eval (car p) d) 13)) (+ 1 3))";
-    let result = eval(env, Rc::new(grammar::TermParser::new().parse(input).unwrap()));
+    let input = "(= 17 ((vau d p (+ (eval (car p) d) 13)) (+ 1 3)))";
+    //let input = "(if (= 2 2) (+ 1 2) (+ 3 4))";
+    //let input = "(quote a)";
+    //let input = "'a";
+    let parsed_input = grammar::TermParser::new().parse(input).unwrap();
+    println!("Parsed input is {:?}", parsed_input);
+    let result = eval(env, Rc::new(parsed_input));
     println!("Result is {:?}", result);
 }