Improved history storage

src/context.rs

@@ -0,0 +1,31 @@
+use crate::parser::Token;
+use std::collections::HashMap;
+
+#[derive(Debug)]
+pub struct Context {
+	history: Vec<Token>,
+	variables: HashMap<String, Token>
+}
+
+impl Context {
+	pub fn new() -> Context {
+		Context{ history: Vec::new(), variables: HashMap::new() }
+	}
+
+	pub fn push_hist(&mut self, t: Token) { self.history.push(t); }
+	pub fn push_var(&mut self, s: String, t: Token) { self.variables.insert(s, t); }
+	pub fn del_var(&mut self, s: &String) { self.variables.remove(s); }
+
+	pub fn get_variable(&self, s: String) -> Option<Token> {
+
+		let v: Option<&Token>;
+
+		if s == "ans" {
+			v = self.history.last();
+		} else {
+			v = self.variables.get(&s);
+		}
+
+		if v.is_some() { Some(v.unwrap().clone()) } else { None }
+	}
+}