From 1da08c0a43083bfbace5093c715010c7fc8eb90c Mon Sep 17 00:00:00 2001
From: Felix Martin <mail@felixm.de>
Date: Sun, 30 May 2021 12:25:20 -0400
Subject: [PATCH] Implement PartialEq and PartialOrd resolves #7

---
 .gitignore         |  1 +
 src/environment.rs |  6 +-----
 src/interpreter.rs |  2 ++
 src/parser.rs      | 21 +++++++++++++++++++++
 src/primitives.rs  | 27 +++++++++++++++------------
 5 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/.gitignore b/.gitignore
index 765cf3b..605cef0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,4 @@
 **/*.rs.bk
 
 .vscode
+test.scm
diff --git a/src/environment.rs b/src/environment.rs
index 0afdb2d..abac38f 100644
--- a/src/environment.rs
+++ b/src/environment.rs
@@ -19,6 +19,7 @@ pub fn get_global_environment<'a>() -> Env<'a> {
             (make_symbol("*"), Datum::Procedure(primitives::mul)),
             (make_symbol("-"), Datum::Procedure(primitives::sub)),
             (make_symbol("="), Datum::Procedure(primitives::eq)),
+            (make_symbol("<"), Datum::Procedure(primitives::lt)),
         ],
         outer: None,
     }
@@ -80,8 +81,3 @@ pub fn extend<'a>(vars: Datum, vals: Datum, env: &'a Env) -> Env<'a> {
         outer: Some(env),
     }
 }
-
-// pub fn shrink_environment(env: &mut Env) -> Datum {
-//     env.pop();
-//     Datum::Unspecified
-// }
diff --git a/src/interpreter.rs b/src/interpreter.rs
index ecbbfc7..1977b1f 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -61,6 +61,8 @@ fn interpret_define(args: &Vec<Datum>, env: &mut Env) -> Datum {
                     panic!("INTERPRET-DEFINE -- parameter not a symbol {:?}", p);
                 }
             }
+            // FIXME: we need to keep the current environment here otherwise closures will not work
+            // FIXME: also create a dedicated enum-type for procedures instead of putting it into a vector
             let lambda_parameters = Datum::List(parameters);
             let lambda_body = Datum::List(args[2..].to_vec());
             let lambda = Datum::List(vec![make_symbol("lambda"), lambda_parameters, lambda_body]);
diff --git a/src/parser.rs b/src/parser.rs
index a0bb0bc..d9bf201 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -1,5 +1,6 @@
 use crate::lexer::Token;
 use crate::lexer::Tokens;
+use std::cmp::Ordering;
 
 #[derive(Debug, Clone)]
 pub enum Datum {
@@ -21,6 +22,26 @@ impl Default for Datum {
     }
 }
 
+impl PartialEq for Datum {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Datum::Boolean(b1), Datum::Boolean(b2)) => b1 == b2,
+            (Datum::Number(n1), Datum::Number(n2)) => n1 == n2,
+            _ => false,
+        }
+    }
+}
+
+impl PartialOrd for Datum {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        match (self, other) {
+            (Datum::Boolean(b1), Datum::Boolean(b2)) => Some(b1.cmp(b2)),
+            (Datum::Number(n1), Datum::Number(n2)) => Some(n1.cmp(n2)),
+            _ => None,
+        }
+    }
+}
+
 pub fn parse(tokens: Tokens) -> Datum {
     let (datum, _) = parse_datum(&tokens, 0);
     datum
diff --git a/src/primitives.rs b/src/primitives.rs
index 3bd0427..0cd7744 100644
--- a/src/primitives.rs
+++ b/src/primitives.rs
@@ -62,20 +62,23 @@ pub fn eq(args: Vec<Datum>) -> Datum {
         Boolean(true)
     } else {
         let first = &args[1];
-
         for i in 2..args.len() {
             let current = &args[i];
-            match (first, current) {
-                (Boolean(b1), Boolean(b2)) => {
-                    return Boolean(b1 == b2);
-                }
-                (Number(n1), Number(n2)) => {
-                    return Boolean(n1 == n2);
-                }
-                _ => {
-                    println!("{:?} is not equal to {:?}", first, current);
-                    return Boolean(false);
-                }
+            if first != current {
+                return Boolean(false);
+            }
+        }
+        Boolean(true)
+    }
+}
+
+pub fn lt(args: Vec<Datum>) -> Datum {
+    if args.len() == 1 {
+        Boolean(true)
+    } else {
+        for i in 1..(args.len() - 1) {
+            if &args[i] >= &args[i + 1] {
+                return Boolean(false);
             }
         }
         Boolean(true)