Removed the struct MathParser. The regular Parser struct does does its job now.

src/interpreter.rs

@@ -5,17 +5,17 @@ use crate::parser::{Expr, Stmt, Unit};
 use crate::prelude::{self, Prelude};
 use crate::visitor::Visitor;
 
-pub struct Interpreter {
-    pub symbol_table: HashMap<String, Stmt>,
+pub struct Interpreter<'a> {
+    symbol_table: &'a mut HashMap<String, Stmt>,
     angle_unit: Unit,
     prelude: Prelude,
 }
 
-impl Interpreter {
-    pub fn new(angle_unit: Unit) -> Self {
-        let mut hashmap: HashMap<String, Stmt> = HashMap::new();
+impl<'a> Interpreter<'a> {
+    pub fn new(angle_unit: Unit, symbol_table: &'a mut HashMap<String, Stmt>) -> Self {
+        //let mut hashmap: HashMap<String, Stmt> = HashMap::new();
         for constant in prelude::CONSTANTS {
-            hashmap.insert(
+            symbol_table.insert(
                 constant.0.to_string(),
                 Stmt::VarDecl(
                     constant.0.to_string(),
@@ -25,9 +25,9 @@ impl Interpreter {
         }
 
         Interpreter {
-            angle_unit,
-            symbol_table: hashmap,
-            prelude: Prelude::new(),
+            angle_unit: angle_unit.clone(),
+            symbol_table,
+            prelude: Prelude::new(angle_unit),
         }
     }
 
@@ -44,11 +44,6 @@ impl Interpreter {
 
         return None;
     }
-
-    pub fn set_angle_unit(&mut self, angle_unit: Unit) {
-        self.prelude.angle_unit = angle_unit.clone();
-        self.angle_unit = angle_unit;
-    }
 }
 
 impl TokenKind {
@@ -68,7 +63,7 @@ impl Unit {
     }
 }
 
-impl Visitor<f64, f64> for Interpreter {
+impl<'a> Visitor<f64, f64> for Interpreter<'a> {
     fn visit_stmt(&mut self, stmt: &Stmt) -> f64 {
         match stmt {
             Stmt::VarDecl(identifier, _) => {

src/main.rs

@@ -2,12 +2,10 @@ use std::{env, process};
 
 mod interpreter;
 mod lexer;
-mod math_parser;
 mod parser;
 mod prelude;
 mod visitor;
-use math_parser::MathParser;
-use parser::Unit;
+use parser::{Parser, Unit};
 
 use rustyline::error::ReadlineError;
 use rustyline::Editor;
@@ -15,12 +13,12 @@ use rustyline::Editor;
 #[allow(unused_assignments)] // The compiler gives a warning that is not valid.
 fn main() {
     let angle_unit = get_angle_unit();
-    let mut math_parser = MathParser::new();
-    math_parser.set_angle_unit(angle_unit);
+    let mut parser = Parser::new();
+    parser.angle_unit = angle_unit;
 
     // Command line argument input, execute it and exit.
     if let Some(expr) = env::args().skip(1).next() {
-        eval(&mut math_parser, &expr);
+        eval(&mut parser, &expr);
         return;
     }
 
@@ -33,7 +31,7 @@ fn main() {
         match readline {
             Ok(input) => {
                 rl.add_history_entry(input.as_str());
-                eval_repl(&mut math_parser, &input);
+                eval_repl(&mut parser, &input);
             }
             Err(ReadlineError::Interrupted) => break,
             _ => break,
@@ -41,17 +39,17 @@ fn main() {
     }
 }
 
-fn eval_repl(math_parser: &mut MathParser, input: &str) {
+fn eval_repl(parser: &mut Parser, input: &str) {
     match input {
         "" => eprint!(""),
         "clear" => print!("\x1B[2J"),
         "exit" => process::exit(0),
-        _ => eval(math_parser, input),
+        _ => eval(parser, input),
     }
 }
 
-fn eval(math_parser: &mut MathParser, input: &str) {
-    if let Some(result) = math_parser.parse(input) {
+fn eval(parser: &mut Parser, input: &str) {
+    if let Some(result) = parser.parse(input) {
         println!("{}", result);
     }
 }

src/math_parser.rs

@@ -1,30 +0,0 @@
-use crate::interpreter::Interpreter;
-use crate::lexer::Lexer;
-use crate::parser::{Parser, Unit};
-
-pub const DEFAULT_ANGLE_UNIT: Unit = Unit::Radians;
-
-pub struct MathParser {
-    parser: Parser,
-    interpreter: Interpreter,
-}
-
-impl MathParser {
-    pub fn new() -> Self {
-        MathParser {
-            parser: Parser::new(),
-            interpreter: Interpreter::new(DEFAULT_ANGLE_UNIT),
-        }
-    }
-
-    pub fn parse(&mut self, source: &str) -> Option<f64> {
-        let tokens = Lexer::lex(source);
-        let statements = self.parser.parse(tokens);
-
-        self.interpreter.interpret(statements)
-    }
-
-    pub fn set_angle_unit(&mut self, unit: Unit) {
-        self.interpreter.set_angle_unit(unit);
-    }
-}

src/parser.rs

@@ -1,6 +1,10 @@
-use std::mem;
+use std::{collections::HashMap, mem};
 
-use crate::lexer::{Token, TokenKind};
+use crate::{
+    interpreter::Interpreter,
+    lexer::{Lexer, Token, TokenKind},
+    prelude,
+};
 
 #[derive(Debug, Clone)]
 pub enum Stmt {
@@ -27,8 +31,10 @@ pub enum Unit {
 }
 
 pub struct Parser {
+    pub angle_unit: Unit,
     tokens: Vec<Token>,
     pos: usize,
+    symbol_table: HashMap<String, Stmt>,
 }
 
 impl TokenKind {
@@ -49,11 +55,13 @@ impl Parser {
         Parser {
             tokens: Vec::new(),
             pos: 0,
+            symbol_table: HashMap::new(),
+            angle_unit: prelude::DEFAULT_ANGLE_UNIT,
         }
     }
 
-    pub fn parse(&mut self, tokens: Vec<Token>) -> Vec<Stmt> {
-        self.tokens = tokens;
+    pub fn parse(&mut self, input: &str) -> Option<f64> {
+        self.tokens = Lexer::lex(input);
         self.pos = 0;
 
         let mut statements: Vec<Stmt> = Vec::new();
@@ -61,7 +69,7 @@ impl Parser {
             statements.push(self.parse_stmt());
         }
 
-        statements
+        Interpreter::new(self.angle_unit.clone(), &mut self.symbol_table).interpret(statements)
     }
 
     fn parse_stmt(&mut self) -> Stmt {

src/prelude.rs

@@ -1,6 +1,7 @@
-use crate::{math_parser, parser::Unit};
+use crate::parser::Unit;
 use std::collections::HashMap;
 
+pub const DEFAULT_ANGLE_UNIT: Unit = Unit::Radians;
 pub const CONSTANTS: &[(&str, &str)] = &[
     ("pi", "3.14159265"),
     ("π", "3.14159265"),
@@ -66,15 +67,15 @@ fn from_angle_unit(x: f64, angle_unit: &Unit) -> f64 {
 }
 
 pub struct Prelude {
-    pub angle_unit: Unit,
+    angle_unit: Unit,
     unary: HashMap<String, UnaryFuncInfo>,
     binary: HashMap<String, BinaryFuncInfo>,
 }
 
 impl Prelude {
-    pub fn new() -> Self {
+    pub fn new(angle_unit: Unit) -> Self {
         Prelude {
-            angle_unit: math_parser::DEFAULT_ANGLE_UNIT,
+            angle_unit,
             unary: HashMap::new(),
             binary: HashMap::new(),
         }