Add test file, implement and/or/not, prepare for proper compound proc

.gitignore

@@ -7,4 +7,3 @@
 **/*.rs.bk
 
 .vscode
-test.scm

README.md

@@ -1,3 +1,9 @@
 # schemers
 
-A crude Scheme interpreter implemented for SICP exercise 5.51.
+A crude Scheme interpreter implemented for SICP exercise 5.51.
+
+```bash
+cargo build
+./target/debug/schemers test.scm
+```
+

src/environment.rs

@@ -22,6 +22,9 @@ pub fn get_global_environment<'a>() -> Env<'a> {
             (make_symbol("-"), Primitive(sub)),
             (make_symbol("="), Primitive(eq)),
             (make_symbol("<"), Primitive(lt)),
+            (make_symbol("or"), Primitive(or)),
+            (make_symbol("and"), Primitive(and)),
+            (make_symbol("not"), Primitive(not)),
             (make_symbol("list"), Primitive(list)),
             (make_symbol("cons"), Primitive(cons)),
             (make_symbol("car"), Primitive(car)),

src/interpreter.rs

@@ -3,7 +3,7 @@ use crate::environment::Env;
 use crate::parser::Datum;
 use crate::parser::Datum::*;
 
-fn is_true(exp: &Datum) -> bool {
+pub fn is_true(exp: &Datum) -> bool {
     match exp {
         Boolean(b) => *b,
         Number(_) => true,
@@ -72,14 +72,13 @@ fn interpret_define(args: &Vec<Datum>, env: &mut Env) -> Datum {
                 }
             }
 
-            // XXX: A procedure is clearly not a lambda. We have to keep the
-            // scope of the definition. Otherwise, closures won't work.
-            let lambda_body = args[2..].to_vec();
-            let lambda = Lambda {
+            // XXX: a procedure includes the current environment
+            let body = args[2..].to_vec();
+            let proc = Procedure {
                 parameters: parameters,
-                body: lambda_body,
+                body: body,
             };
-            environment::define_variable(definition_var, lambda, env)
+            environment::define_variable(definition_var, proc, env)
         }
         _ => panic!("INTERPRET-DEFINE -- cannot define {:?}", args),
     }
@@ -157,7 +156,7 @@ fn interpret_application(vec: &Vec<Datum>, env: &mut Env) -> Datum {
 
     match &args[0] {
         Primitive(proc) => proc(args),
-        Lambda { parameters, body } => {
+        Lambda { parameters, body } | Procedure { parameters, body } => {
             let lambda_args = args[1..].to_vec();
             let mut new_env =
                 environment::extend(List(parameters.to_vec()), List(lambda_args), env);

src/main.rs

@@ -42,8 +42,8 @@ fn interpret_file(filename: &Path) {
             let tokens = lexer::read(scm_code.as_str());
             let datum = parser::parse(tokens);
             let mut env = environment::get_global_environment();
-            let result = interpreter::interpret(&datum, &mut env);
-            println!("{:?}", result);
+            let _result = interpreter::interpret(&datum, &mut env);
+            // println!("{:?}", result);
         }
         Err(error) => println!("error: {} {:?}", error, filename),
     }
@@ -51,8 +51,7 @@ fn interpret_file(filename: &Path) {
 
 fn main() {
     let args: Vec<String> = env::args().collect();
-    // let scm_code = "(begin (define (f n) (if (= n 1) 1 (* n (f (- n 1))))) (f 10))";
-    let scm_code = "(let ((a 3) (b 4)) (define c (+ a b)) (* c c))";
+    let scm_code = "";
 
     if args.len() == 2 {
         let arg_path = Path::new(&args[1]);

src/parser.rs

@@ -16,6 +16,10 @@ pub enum Datum {
         parameters: Vec<Datum>,
         body: Vec<Datum>,
     },
+    Procedure {
+        parameters: Vec<Datum>,
+        body: Vec<Datum>,
+    },
     Unspecified,
 }
 
@@ -42,7 +46,8 @@ impl PartialEq for Datum {
 impl fmt::Display for Datum {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            Datum::Boolean(b) => write!(f, "{}", b),
+            Datum::Boolean(true) => write!(f, "#t"),
+            Datum::Boolean(false) => write!(f, "#f"),
             Datum::Number(n) => write!(f, "{}", n),
             Datum::Symbol(s) => write!(f, "{}", s),
             Datum::String(s) => write!(f, "{}", s),

src/primitives.rs

@@ -1,4 +1,5 @@
 use crate::interpreter::has_tag;
+use crate::interpreter::is_true;
 use crate::parser::make_symbol;
 use crate::parser::Datum;
 use crate::parser::Datum::*;
@@ -89,6 +90,44 @@ pub fn lt(args: Vec<Datum>) -> Datum {
     }
 }
 
+pub fn or(args: Vec<Datum>) -> Datum {
+    if args.len() == 1 {
+        Boolean(false)
+    } else {
+        for i in 1..args.len() {
+            if is_true(&args[i]) {
+                return args[i].clone();
+            }
+        }
+        Boolean(false)
+    }
+}
+
+pub fn and(args: Vec<Datum>) -> Datum {
+    if args.len() == 1 {
+        Boolean(true)
+    } else {
+        for i in 1..args.len() {
+            if !is_true(&args[i]) {
+                return Boolean(false);
+            }
+        }
+        args[args.len() - 1].clone()
+    }
+}
+
+pub fn not(args: Vec<Datum>) -> Datum {
+    if args.len() != 2 {
+        panic!("NOT -- takes one argument");
+    } else {
+        if is_true(&args[1]) {
+            Boolean(false)
+        } else {
+            Boolean(true)
+        }
+    }
+}
+
 pub fn display(args: Vec<Datum>) -> Datum {
     for i in 1..args.len() {
         print!("{}", args[i]);

test.scm

@@ -0,0 +1,43 @@
+(begin
+  (define (newline) (display "\n"))
+  (display (or #t #f)) (newline)
+  (display (and #t #f)) (newline)
+  (display (not #f)) (newline)
+  (define a 5)
+  (define (fib n)
+    (cond
+      ((< n 0) (display "WARNING: n smaller than 0"))
+      ((< n 3) 1)
+      (else (+ (fib (- n 2)) (fib (- n 1))))))
+  (define (fac n) (if (= n 1) 1 (* n (fac (- n 1)))))
+  (set! a (+ a a))
+  (define l (list a (* 3 3) (+ a a)))
+  (begin
+    (display "(fac ") (display a)
+    (display ") -> ") (display (fac a)) (display "\n"))
+  (begin
+    (display "(fib ") (display a)
+    (display ") -> ") (display (fib a)) (display "\n"))
+  (define l (cons 'a l))
+  (display l) (newline)
+  (display (cons 'a 'b)) (newline)
+  (display (car l)) (newline)
+  (display (cdr (cdr l))) (newline)
+  (display (pair? l)) (newline)
+  (display (pair? 'a)) (newline)
+  (display ((lambda (x y) (* x a)) 3 5)) (newline)
+  (display
+    (let ((a (+ a a))
+          (b (* a a))
+          (x 42))
+      (+ a b x)))
+  (newline)
+  (define (p)
+    (define a 42)
+    (define (f) a)
+    f)
+  (display ((p))) ; should return 42
+  (newline)
+  'done
+  )
+