[refactor] Adding a new definition for environment.

Author: rbonifacio

src/environment.rs

@@ -0,0 +1 @@
+pub mod environment;

src/environment/environment.rs

@@ -0,0 +1,102 @@
+
+use crate::ir::ast::Function;
+use crate::ir::ast::Name;
+
+use std::collections::HashMap;
+use std::collections::LinkedList;
+
+pub struct Scope<A> {
+    pub variables: HashMap<Name, A>,
+    pub functions: HashMap<Name, Function>
+}
+
+impl<A> Scope<A> {
+    fn new() -> Scope<A> {
+	Scope { variables: HashMap::new(), functions: HashMap::new() }
+    }
+
+    fn map_variable(&mut self, var: Name, value: A) -> () {
+	self.variables.insert(var, value);
+	return ()
+    }
+
+    fn lookup(&mut self, var: Name) -> Option<&A> {
+	self.variables.get(&var)
+    }
+}
+
+pub struct Environment<A> {
+    pub globals: Scope<A>,
+    pub stack: LinkedList<Scope<A>>
+}
+
+impl<A> Environment<A> {
+
+    pub fn new() -> Environment<A> {
+	Environment { globals: Scope::new(), stack: LinkedList::new() }
+    }
+    
+    pub fn map_variable(&mut self, var: Name, value: A) -> () {
+	match self.stack.front_mut() {
+	    None => self.globals.map_variable(var, value),
+	    Some(top) => top.map_variable(var, value)
+		
+	};
+	return ()
+    }
+
+    pub fn lookup(&mut self, var: Name) -> Option<&A> {
+	match self.stack.front_mut() {
+	    None => self.globals.lookup(var),
+	    Some(top) => top.lookup(var)
+	}
+    }
+
+    pub fn push(&mut self) -> () {
+	self.stack.push_front(Scope::new());
+    }
+
+    pub fn pop(&mut self) -> () {
+	self.stack.pop_front();
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use crate::environment::environment::{Scope, Environment};
+    
+    #[test]
+    fn eval_map_and_lookup_var() {
+	let mut s: Scope<i32> = Scope::new();
+
+	s.map_variable("x".to_string(), 32);
+	s.map_variable("y".to_string(), 23);
+	
+	assert_eq!(Some(32), s.lookup("x".to_string()).copied());
+	assert_eq!(Some(23), s.lookup("y".to_string()).copied());
+    }
+
+    #[test]
+    fn eval_environment() {
+	let mut env: Environment<i32> = Environment::new();
+
+	env.map_variable("x".to_string(), 32);
+
+	env.push();
+
+	env.map_variable("x".to_string(), 55);
+	env.map_variable("y".to_string(), 23);
+	
+	assert_eq!(Some(55), env.lookup("x".to_string()).copied());
+	assert_eq!(Some(23), env.lookup("y".to_string()).copied());
+	assert_eq!(None, env.lookup("a".to_string()).copied());
+
+	env.pop();
+
+	assert_eq!(Some(32), env.lookup("x".to_string()).copied());
+	assert_eq!(None, env.lookup("y".to_string()).copied());
+    }
+    
+
+}

src/main.rs

@@ -14,6 +14,7 @@ pub mod interpreter;
 pub mod ir;
 pub mod parser;
 pub mod tc;
+pub mod environment;
 
 fn main() {
     println!("Hello, world!");