Reorganized code, added basic error handling

src/main.rs

@@ -4,6 +4,8 @@ use std::io::Write;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, Ordering};
 
+
+
 use termcolor::{
 	Color,
 	ColorChoice,
@@ -13,6 +15,9 @@ use termcolor::{
 };
 
 mod parser;
+use crate::parser::Token;
+//use crate::parser::ParserError;
+use crate::parser::LineLocation;
 
 const PROMPT_PREFIX: &str = "==> ";
 
@@ -77,23 +82,26 @@ fn main() -> Result<(), std::io::Error> {
 			continue;
 		}
 
-		// Tokenize input.
+		// Parse input.
 		// Fail if we encounter invalid characters.
-		let mut g = match parser::tokenize::tokenize(&input) {
-			Ok(v) => v,
-			Err(_) => {
+		let g: Token = match parser::parse(&input) {
+			Ok(g) => g,
+			Err((l, e)) => {
+				let LineLocation{pos, len} = l;
+	
+				let s = " ";
+				let m = "^";
+				println!("{}{} {:?}", s.repeat(pos + 4), m.repeat(len), e);
+				stdout.flush()?;
 				continue;
 			}
 		};
 
-
 		stdout.set_color(ColorSpec::new().set_fg(Some(Color::Green)))?;
 		write!(stdout, "\n  => ")?;
 		stdout.reset()?;
 		write!(stdout, "Got {input}\n\n\n")?;
-		
-		parser::parse(&mut g).expect("Could not parse");
-
+	
 		writeln!(stdout, "Tokenized: {g:#?}")?;
 	}
 

src/parser.rs

@@ -1,18 +1,67 @@
-pub mod tokenize;
+mod tokenize;
 mod replace_pre;
 mod fold_operators;
 mod unwrap_groups;
 
-use crate::parser::tokenize::Token;
+use crate::parser::tokenize::tokenize;
 use crate::parser::replace_pre::replace_pre;
 use crate::parser::fold_operators::fold_operators;
 use crate::parser::unwrap_groups::unwrap_groups;
 
+use std::collections::VecDeque;
 
-pub fn parse(g: &mut Token) -> Result<(), ()> {
-	replace_pre(g)?;
-	fold_operators(g)?;
-	unwrap_groups(g)?;
 
-	return Ok(());
+#[derive(Debug)]
+pub enum Token {
+
+	// Used only while tokenizing.
+	// All of these are replaced with one of the tokens below.
+	//
+	// If parsing is successful,
+	//  - all PreGroups will vanish
+	//  - all PreOperators will become Operators
+	//  - all PreNumbers will become Numbers
+	PreGroup(LineLocation, VecDeque<Token>),
+	PreOperator(LineLocation, String),
+	PreNumber(LineLocation, String),
+	PreWord(LineLocation, String),
+
+	Number(f64),
+
+	// Operators
+	Multiply(VecDeque<Token>),
+	Divide(VecDeque<Token>),
+	Add(VecDeque<Token>),
+	Subtract(VecDeque<Token>),
+	Factorial(VecDeque<Token>),
+	Negative(VecDeque<Token>),
+	Power(VecDeque<Token>),
+	Modulo(VecDeque<Token>),
+}
+
+#[derive(Debug)]
+#[derive(Copy, Clone)]
+pub struct LineLocation {
+	pub pos: usize,
+	pub len: usize
+}
+
+#[derive(Debug)]
+pub enum ParserError {
+	InvalidChar,
+	MissingCloseParen,
+	Syntax,
+	BadNumber  // Cannot parse a number
+}
+
+
+
+pub fn parse(s: &String) -> Result<Token, (LineLocation, ParserError)> {
+
+	let mut g: Token = tokenize(s)?;
+	replace_pre(&mut g)?;
+	fold_operators(&mut g)?;
+	unwrap_groups(&mut g)?;
+	
+	return Ok(g);
 }

src/parser/fold_operators.rs

@@ -1,5 +1,10 @@
 use std::collections::VecDeque;
-use crate::parser::tokenize::Token;
+
+use crate::parser::Token;
+use crate::parser::LineLocation;
+use crate::parser::ParserError;
+
+
 
 enum OperatorType {
 	Binary,    // A binary operator, like a + b
@@ -12,7 +17,7 @@ fn fold_operators_once(
 	op_type: &OperatorType,
 	check: fn(&str) -> bool,
 	new_token: fn(&str, VecDeque<Token>) -> Token,
-) -> Result<(), ()> {
+) -> Result<(), (LineLocation, ParserError)> {
 
 	// Groups to process
 	let mut t_vec: VecDeque<&mut Token> = VecDeque::with_capacity(32);
@@ -122,7 +127,7 @@ fn fold_operators_once(
 	return Ok(());
 }
 
-pub fn fold_operators(exp: &mut Token) -> Result<(), ()> {
+pub fn fold_operators(exp: &mut Token) -> Result<(), (LineLocation, ParserError)> {
 	fold_operators_once(
 		exp, &OperatorType::UnaryLeft,
 		|s| s=="!",

src/parser/replace_pre.rs

@@ -1,6 +1,9 @@
-use crate::parser::tokenize::Token;
+use crate::parser::Token;
+use crate::parser::LineLocation;
+use crate::parser::ParserError;
 
-pub fn replace_pre(g: &mut Token) -> Result<(), ()> {
+
+pub fn replace_pre(g: &mut Token) -> Result<(), (LineLocation, ParserError)> {
 
 	match g {
 		Token::PreGroup(_, ref mut vec) => {
@@ -8,10 +11,10 @@ pub fn replace_pre(g: &mut Token) -> Result<(), ()> {
 				replace_pre(i)?;
 			}
 		},
-		Token::PreNumber(_, s) => {
+		Token::PreNumber(l, s) => {
 			let n = match s.parse() {
 				Ok(n) => n,
-				Err(_) => panic!()
+				Err(_) => return Err((*l, ParserError::BadNumber))
 			};
 			*g = Token::Number(n);
 		}
@@ -19,8 +22,7 @@ pub fn replace_pre(g: &mut Token) -> Result<(), ()> {
 			if s == "mod" {
 				*g = Token::PreOperator(*l, String::from("mod"));
 			} else {
-				return Err(());
-				//new.push_back(t);
+				return Err((*l, ParserError::Syntax));
 			}
 		},
 		Token::PreOperator(_, _) => {},

src/parser/tokenize.rs

@@ -1,44 +1,8 @@
 use std::collections::VecDeque;
 
-#[derive(Debug)]
-#[derive(Copy, Clone)]
-pub struct LineLocation {
-	pos: usize,
-	len: usize
-}
-
-#[derive(Debug)]
-pub enum Token {
-
-	// Only used after tokenizing
-	PreGroup(LineLocation, VecDeque<Token>),
-	PreOperator(LineLocation, String),
-	PreNumber(LineLocation, String),
-	PreWord(LineLocation, String),
-
-	// All PreGroups should vanish after operator folding
-	// All PreOperators should become Operators
-	// All PreNumbers should become Numbers
-	// All PreWords should become TODO.
-
-	// Only used in tree
-
-	Number(f64),
-
-	// Functions
-
-	// Operators	
-	Multiply(VecDeque<Token>),
-	Divide(VecDeque<Token>),
-	Add(VecDeque<Token>),
-	Subtract(VecDeque<Token>),
-	Factorial(VecDeque<Token>),
-	Negative(VecDeque<Token>),
-	Power(VecDeque<Token>),
-	Modulo(VecDeque<Token>),
-
-	//Function(String, VecDeque<Token>),
-}
+use crate::parser::Token;
+use crate::parser::LineLocation;
+use crate::parser::ParserError;
 
 #[inline(always)]
 fn update_line_location(mut t: Token, stop_i: usize) -> Token {
@@ -60,16 +24,8 @@ fn update_line_location(mut t: Token, stop_i: usize) -> Token {
 }
 
 
-/// Turn a string into a set of tokens.
-/// Does not check syntax. Fails if `input` contains an invalid character.
-//
-// # Arguments:
-// `input`: A string like `(-3*2.2)/3`
-//
-// # Returns:
-// * `Ok(Vec<token>)` if we were successful.
-// * `Err(())` if we couldn't tokenize this string.
-pub fn tokenize(input: &String) -> Result<Token, ()> {
+
+pub fn tokenize(input: &String) -> Result<Token, (LineLocation, ParserError)> {
 	let mut t: Option<Token> = None; // The current token we're reading
 	let mut g: Vec<Token> = Vec::with_capacity(8); // Vector of "grouping levels"
 	g.push(Token::PreGroup(LineLocation{pos: 0, len: 0}, VecDeque::with_capacity(8)));
@@ -190,7 +146,7 @@ pub fn tokenize(input: &String) -> Result<Token, ()> {
 					_ => panic!()
 				};
 		
-				g_now.push_back(update_line_location(new_group, i));
+				g_now.push_back(update_line_location(new_group, i+1));
 			},
 
 			// Space. Basic seperator.
@@ -199,7 +155,7 @@ pub fn tokenize(input: &String) -> Result<Token, ()> {
 			}
 
 			// Invalid token
-			_ => { return Err(()); }
+			_ => { return Err((LineLocation{pos: i, len: 1}, ParserError::InvalidChar)); }
 		};
 	}
 
@@ -210,5 +166,21 @@ pub fn tokenize(input: &String) -> Result<Token, ()> {
 	};
 	if t.is_some() { g_now.push_back(update_line_location(t.unwrap(), input.len())); }
 
+	if g.len() != 1 {
+		let q: LineLocation = match g.last_mut().unwrap() {
+			Token::PreGroup(l, _) => *l,
+			_ => panic!()
+		};
+
+		let LineLocation{pos:p, ..} = q;
+		return Err((
+			LineLocation{
+				pos: p,
+				len: input.len() - p
+			},
+			ParserError::MissingCloseParen
+		))
+	}
+
 	return Ok(g.pop().unwrap());
 }

src/parser/unwrap_groups.rs

@@ -1,12 +1,14 @@
-use crate::parser::tokenize::Token;
+use crate::parser::Token;
+use crate::parser::ParserError;
+use crate::parser::LineLocation;
 
-pub fn unwrap_groups(g: &mut Token) -> Result<(), ()> {
+pub fn unwrap_groups(g: &mut Token) -> Result<(), (LineLocation, ParserError)> {
 
 	match g {
 		// If g is a PreGroup, unwrap it
-		Token::PreGroup(_, ref mut vec) => {
+		Token::PreGroup(l, ref mut vec) => {
 			if vec.len() != 1 {
-				panic!();
+				return Err((*l, ParserError::Syntax));
 			}
 			
 			let mut i = vec.pop_front().unwrap();