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Modularize Tokenizer's iterator for improved readability (#2053)

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While learning Rust and going through the course, I realized the
exercise solution readability can be improved by adding Tokenizer helper
methods to encapsulate the character collecting logic - which slims down
iterator's next() method while enhancing clarity.
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snazzybytes 2024-05-06 12:32:05 -04:00 committed by GitHub
parent 3d99e1badf
commit b6343d0522
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1 changed files with 44 additions and 32 deletions
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76
src/error-handling/exercise.rs
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@ -57,28 +57,34 @@ enum TokenizerError {
struct Tokenizer<'a>(Peekable<Chars<'a>>);
impl<'a> Tokenizer<'a> {
fn collect_number(&mut self, first_char: char) -> Token {
let mut num = String::from(first_char);
while let Some(&c @ '0'..='9') = self.0.peek() {
num.push(c);
self.0.next();
}
Token::Number(num)
}
fn collect_identifier(&mut self, first_char: char) -> Token {
let mut ident = String::from(first_char);
while let Some(&c @ ('a'..='z' | '_' | '0'..='9')) = self.0.peek() {
ident.push(c);
self.0.next();
}
Token::Identifier(ident)
}
}
impl<'a> Iterator for Tokenizer<'a> {
type Item = Result<Token, TokenizerError>;
fn next(&mut self) -> Option<Result<Token, TokenizerError>> {
let c = self.0.next()?;
match c {
'0'..='9' => {
let mut num = String::from(c);
while let Some(c @ '0'..='9') = self.0.peek() {
num.push(*c);
self.0.next();
}
Some(Ok(Token::Number(num)))
}
'a'..='z' => {
let mut ident = String::from(c);
while let Some(c @ ('a'..='z' | '_' | '0'..='9')) = self.0.peek() {
ident.push(*c);
self.0.next();
}
Some(Ok(Token::Identifier(ident)))
}
'0'..='9' => Some(Ok(self.collect_number(c))),
'a'..='z' | '_' => Some(Ok(self.collect_identifier(c))),
'+' => Some(Ok(Token::Operator(Op::Add))),
'-' => Some(Ok(Token::Operator(Op::Sub))),
_ => Some(Err(TokenizerError::UnexpectedCharacter(c))),
@ -144,28 +150,34 @@ fn tokenize(input: &str) -> Tokenizer {
struct Tokenizer<'a>(Peekable<Chars<'a>>);
impl<'a> Tokenizer<'a> {
fn collect_number(&mut self, first_char: char) -> Token {
let mut num = String::from(first_char);
while let Some(&c @ '0'..='9') = self.0.peek() {
num.push(c);
self.0.next();
}
Token::Number(num)
}
fn collect_identifier(&mut self, first_char: char) -> Token {
let mut ident = String::from(first_char);
while let Some(&c @ ('a'..='z' | '_' | '0'..='9')) = self.0.peek() {
ident.push(c);
self.0.next();
}
Token::Identifier(ident)
}
}
impl<'a> Iterator for Tokenizer<'a> {
type Item = Token;
fn next(&mut self) -> Option<Token> {
let c = self.0.next()?;
match c {
'0'..='9' => {
let mut num = String::from(c);
while let Some(c @ '0'..='9') = self.0.peek() {
num.push(*c);
self.0.next();
}
Some(Token::Number(num))
}
'a'..='z' => {
let mut ident = String::from(c);
while let Some(c @ ('a'..='z' | '_' | '0'..='9')) = self.0.peek() {
ident.push(*c);
self.0.next();
}
Some(Token::Identifier(ident))
}
'0'..='9' => Some(self.collect_number(c)),
'a'..='z' => Some(self.collect_identifier(c)),
'+' => Some(Token::Operator(Op::Add)),
'-' => Some(Token::Operator(Op::Sub)),
_ => panic!("Unexpected character {c}"),