Added the env and evaluation for addition and subtraction functions

src/env.rs

@@ -0,0 +1,30 @@
+use std::collections::HashMap;
+
+use crate::{Symbol, Value};
+
+#[derive(Default, Debug, Clone)]
+pub struct Environment {
+    symbols: HashMap<Symbol, Value>,
+    outer: Box<Option<Environment>>,
+}
+
+impl Environment {
+    pub fn new() -> Self {
+        Self {
+            outer: Box::new(None),
+            ..Default::default()
+        }
+    }
+
+    pub fn insert_symbol(&mut self, symbol: Symbol, value: Value) {
+        self.symbols.insert(symbol, value);
+    }
+
+    pub fn get_symbol(&self, symbol: &Symbol) -> &Value {
+        if let Some(value) = self.symbols.get(symbol) {
+            value
+        } else {
+            &Value::Nil
+        }
+    }
+}

src/macros.rs

@@ -0,0 +1,8 @@
+macro_rules! insert_symbol {
+    // Takes the env and a symbol in &str form, then it takes a variable list,
+    // of arg types and then a fn to run over them.
+    (&env:expr, &symbol:expr) => {
+        // The macro will expand into the contents of this block.
+        println!("Hello!")
+    };
+}

src/main.rs

@@ -4,11 +4,14 @@ use color_eyre::{
     eyre::{eyre, ContextCompat},
     Result,
 };
+use env::Environment;
 use printer::print;
 use reader::read;
 use regex::Regex;
 use rustyline::{config::Configurer, error::ReadlineError, Editor};
 
+pub mod env;
+pub mod macros;
 pub mod printer;
 pub mod reader;
 pub mod types;
@@ -19,28 +22,55 @@ fn main() -> Result<()> {
     if rl.load_history(".mal-history").is_err() {
         eprintln!("No previous history.");
     }
-
     rl.set_edit_mode(rustyline::EditMode::Vi);
-    let mut env = Environment::default();
-    env.symbols.insert(
+
+    let mut env = Environment::new();
+    env.insert_symbol(
         Symbol::from("+"),
         Value::func(|args| {
-            let total = args
+            let nums: Vec<i64> = args
                 .iter()
                 .map(|a| match a {
                     Value::Number(a) => Ok(*a),
                     _ => Err(eyre!("Should be a number")),
                 })
-                .sum();
-            total
+                .flatten()
+                .collect();
+            let total = nums
+                .into_iter()
+                .reduce(|acc, e| acc + e)
+                .expect("shouldn't fail");
+            Ok(Value::from(total))
         }),
     );
+    env.insert_symbol(
+        Symbol::from("-"),
+        Value::func(|args| {
+            let nums: Vec<i64> = args
+                .iter()
+                .map(|a| match a {
+                    Value::Number(a) => Ok(*a),
+                    _ => Err(eyre!("Should be a number")),
+                })
+                .flatten()
+                .collect();
+            let total = nums
+                .into_iter()
+                .reduce(|acc, n| acc - n)
+                .expect("shouldn't fail");
+            Ok(Value::from(total))
+        }),
+    );
+
     loop {
         let entry = rl.readline(">> ");
         match entry {
             Ok(line) => {
                 rl.add_history_entry(line.as_str())?;
-                read_eval_print(line.as_str(), &env)?;
+                match read_eval_print(line.as_str(), &env) {
+                    Ok(s) => println!("{s}"),
+                    Err(e) => eprintln!("{e}"),
+                }
             }
             Err(ReadlineError::Interrupted) => {
                 println!("CTRL-C");
@@ -59,35 +89,30 @@ fn main() -> Result<()> {
     Ok(())
 }
 
-#[derive(Default, Debug, Clone)]
-pub struct Environment {
-    symbols: HashMap<Symbol, Value>,
-    outer: Box<Environment>,
-}
-
-fn read_eval_print(str: &str, env: &Environment) -> Result<()> {
-    print(&eval(&read(str), env).unwrap());
-    Ok(())
+fn read_eval_print(str: &str, env: &Environment) -> Result<String> {
+    Ok(print(&eval(&read(str), env)?))
 }
 
 fn eval(expr: &Value, env: &Environment) -> Result<Value> {
     match expr {
         Value::Symbol(s) => {
-            if let Some(symbol) = env.symbols.get(&s) {
-                Ok(symbol.clone())
-            } else {
-                Err(eyre!("No symbol here"))
-            }
+            let symbol = env.get_symbol(s).to_owned();
+            Ok(symbol)
         }
         Value::List(list) => {
             let mut args = vec![];
-            let func = &list[0];
-            for value in 1..list.len() {
-                if let Ok(return_value) = eval(&list[value], env) {
-                    args.push(return_value)
+            let first = &list[0];
+            if let Value::List(_) = first {
+                eval(first, env)
+            } else {
+                let first = eval(first, env)?;
+                for value in list.iter().skip(1) {
+                    if let Ok(return_value) = eval(value, env) {
+                        args.push(return_value)
+                    }
                 }
+                first.apply(args)
             }
-            func.apply(args)
         }
         value => Ok(value.to_owned()),
     }

src/types.rs

@@ -88,6 +88,18 @@ impl From<&String> for Value {
     }
 }
 
+impl From<i64> for Value {
+    fn from(num: i64) -> Self {
+        Self::Number(num)
+    }
+}
+
+impl From<&i64> for Value {
+    fn from(num: &i64) -> Self {
+        Self::Number(*num)
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct Symbol(pub String);