Added "ans" variable

src/entry/unix/unix.rs

@@ -21,16 +21,18 @@ use crate::evaluate::EvalError;
 
 
 
+
 #[inline(always)]
 fn do_expression(
 	stdout: &mut RawTerminal<std::io::Stdout>,
-	s: &String
-) -> Result<(), std::io::Error> {
+	s: &String,
+	history: &Vec<parser::Token>
+) -> Result<parser::Token, ()> {
 	#[cfg(debug_assertions)]
-	RawTerminal::suspend_raw_mode(&stdout)?;
+	RawTerminal::suspend_raw_mode(&stdout).unwrap();
 	let g = parser::parse(&s);
 	#[cfg(debug_assertions)]
-	RawTerminal::activate_raw_mode(&stdout)?;
+	RawTerminal::activate_raw_mode(&stdout).unwrap();
 
 	// Check for parse errors
 	if let Err((l, e)) = g {
@@ -41,8 +43,8 @@ fn do_expression(
 			"^".repeat(l.len),
 			e.to_string(),
 			color::Fg(color::Reset),
-		)?;
-		return Ok(());
+		).unwrap();
+		return Err(());
 	}
 
 	let Ok(g) = g else {panic!()};
@@ -54,15 +56,15 @@ fn do_expression(
 		style::Bold, color::Fg(color::Magenta),
 		style::Reset, color::Fg(color::Reset),
 		g.to_string()
-	)?;
+	).unwrap();
 
 
 	// Evaluate expression
 	#[cfg(debug_assertions)]
-	RawTerminal::suspend_raw_mode(&stdout)?;
-	let g = evaluate(&g);
+	RawTerminal::suspend_raw_mode(&stdout).unwrap();
+	let g = evaluate(&g, history);
 	#[cfg(debug_assertions)]
-	RawTerminal::activate_raw_mode(&stdout)?;
+	RawTerminal::activate_raw_mode(&stdout).unwrap();
 
 	// Show output
 	if let Ok(q) = g {
@@ -73,7 +75,9 @@ fn do_expression(
 			style::Reset,
 			q.to_string_outer(),
 			color::Fg(color::Reset)
-		)?;
+		).unwrap();
+		return Ok(q);
+
 	} else {
 		match g {
 			Ok(_) => panic!(),
@@ -85,7 +89,7 @@ fn do_expression(
 					color::Fg(color::Red),
 					style::Reset,
 					color::Fg(color::Reset),
-				)?;
+				).unwrap();
 			},
 
 			Err(EvalError::ZeroDivision) => {
@@ -95,7 +99,7 @@ fn do_expression(
 					color::Fg(color::Red),
 					style::Reset,
 					color::Fg(color::Reset),
-				)?;
+				).unwrap();
 			},
 
 			Err(EvalError::BadMath) => {
@@ -105,7 +109,7 @@ fn do_expression(
 					color::Fg(color::Red),
 					style::Reset,
 					color::Fg(color::Reset),
-				)?;
+				).unwrap();
 			},
 
 			Err(EvalError::IncompatibleUnit) => {
@@ -115,14 +119,22 @@ fn do_expression(
 					color::Fg(color::Red),
 					style::Reset,
 					color::Fg(color::Reset),
-				)?;
+				).unwrap();
+			},
+
+			Err(EvalError::NoHistory) => {
+				write!(
+					stdout, "\n  {}{}Evaluation Error: {}There is no previous answer to reference{}\r\n\n",
+					style::Bold,
+					color::Fg(color::Red),
+					style::Reset,
+					color::Fg(color::Reset),
+				).unwrap();
 			}
 		}
 	}
 
-
-
-	return Ok(());
+	return Err(());
 }
 
 
@@ -146,6 +158,8 @@ pub fn main() -> Result<(), std::io::Error> {
 	//write!(stdout, "{:?}", size).unwrap();
 
 	let mut pb: PromptBuffer = PromptBuffer::new(64);
+	let mut history: Vec<parser::Token> = Vec::new();
+
 
 	'outer: loop {
 
@@ -165,7 +179,8 @@ pub fn main() -> Result<(), std::io::Error> {
 						} else if command::is_command(&in_str) {
 							command::do_command(&mut stdout, &in_str)?;
 						} else {
-							do_expression(&mut stdout, &in_str)?;
+							let r = do_expression(&mut stdout, &in_str, &history);
+							if let Ok(t) = r { history.push(t); }
 						}
 
 						break;

src/evaluate/evaluate.rs

@@ -6,7 +6,7 @@ use super::function::eval_function;
 use super::EvalError;
 
 
-pub fn evaluate(t: &Token) -> Result<Token, EvalError> {
+pub fn evaluate(t: &Token, history: &Vec<Token>) -> Result<Token, EvalError> {
 	let mut g = t.clone();
 	let mut coords: Vec<usize> = Vec::with_capacity(16);
 	coords.push(0);
@@ -31,9 +31,18 @@ pub fn evaluate(t: &Token) -> Result<Token, EvalError> {
 				loop {
 					e = match e {
 						Token::Quantity(_) => { break; },
-						Token::Constant(c) => { evaluate(&c.value()).unwrap() }
-						Token::Operator(Operator::Function(f), v) => { eval_function(&f, &v)? }
-						Token::Operator(o, v) => { eval_operator(&o, &v)? }
+						Token::Constant(c) => { evaluate(&c.value(), history).unwrap() },
+						Token::Operator(Operator::Function(f), v) => { eval_function(&f, &v)? },
+						Token::Operator(o, v) => { eval_operator(&o, &v)? },
+						Token::Variable(s) => {
+							if s == "ans" {
+								if history.len() == 0 {
+									return Err(EvalError::NoHistory);
+								} else {
+									history.last().unwrap().clone()
+								}
+							} else { panic!(); }
+						}
 					};
 				}
 
@@ -50,8 +59,10 @@ pub fn evaluate(t: &Token) -> Result<Token, EvalError> {
 
 
 		match h {
-			Token::Operator(_,_) => { coords.push(0); },
-			Token::Constant(_) => { coords.push(0); },
+			Token::Operator(_,_)
+			| Token::Constant(_)
+			| Token::Variable(_)
+			=> { coords.push(0); },
 
 			Token::Quantity(_) => {
 				let l = coords.pop().unwrap();

src/evaluate/mod.rs

@@ -9,5 +9,6 @@ pub enum EvalError {
 	BadMath,
 	TooBig,
 	ZeroDivision,
-	IncompatibleUnit
+	IncompatibleUnit,
+	NoHistory
 }

src/parser/pretoken.rs

@@ -83,6 +83,9 @@ impl PreToken {
 				let c = Unit::from_string(&s);
 				if c.is_some() { return Ok(Token::Quantity(c.unwrap())); }
 
+
+				if s == "ans" { return Ok(Token::Variable(String::from("ans"))); }
+
 				return Err((l, ParserError::Undefined(s)));
 			}
 

src/parser/stage/tokenize.rs

@@ -50,9 +50,9 @@ fn push_token(g: &mut VecDeque<PreToken>, t: Option<PreToken>, stop_i: usize) {
 		}
 	}
 
+	// Some operators are written as words.
 	if let PreToken::PreWord(l, s) = &t {
-		let o = Operator::from_string(s);
-		if o.is_some() {
+		if Operator::from_string(s).is_some() {
 			t = PreToken::PreOperator(*l, s.clone());
 		}
 	}

src/parser/token/token.rs

@@ -8,6 +8,7 @@ use super::Constant;
 #[derive(Debug)]
 #[derive(Clone)]
 pub enum Token {
+	Variable(String),
 	Quantity(Quantity),
 	Constant(Constant),
 	Operator(Operator, VecDeque<Token>),
@@ -18,6 +19,7 @@ impl ToString for Token {
 		match self {
 			Token::Quantity(v) => v.to_string(),
 			Token::Constant(c) => c.to_string(),
+			Token::Variable(s) => s.clone(),
 			Token::Operator(o,a) => o.print(a)
 		}
 	}
@@ -30,6 +32,7 @@ impl Token {
 		match self {
 			Token::Quantity(v) => v.to_string_outer(),
 			Token::Constant(c) => c.to_string(),
+			Token::Variable(s) => s.clone(),
 			Token::Operator(o,a) => o.print(a)
 		}
 	}

src/tests.rs

@@ -9,7 +9,7 @@ fn eval_to_str(s: &str) -> Result<String, ()> {
 	};
 	//let out_str = g.print();
 
-	return match evaluate(&g) {
+	return match evaluate(&g, &Vec::new()) {
 		Ok(x) => Ok(x.to_string_outer()),
 		Err(_) => Err(())
 	};