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Simplify some code in the parsing exercise (#1594)

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`let Some(x) = E else { return None; }` is equivalent to
`let Some(x) = E?`. That latter is shorter and more idiomatic, so let's
use that.

A pattern of the form `c @ P1 | c @ P1` has the disadvantage that the
name `c` is repeated. Let's replace it with `c @ (P1 | P2)`.

An `x: Option<Result<T, E>>` can be handled more succinctly with
`x.ok_or(...)??`.
This commit is contained in:
Martin Huschenbett 2023-12-18 16:03:10 +01:00 committed by GitHub
parent 9a6a16e4ee
commit a35841992e
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1 changed files with 5 additions and 11 deletions
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16
src/error-handling/exercise.rs
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@ -61,9 +61,7 @@ impl<'a> Iterator for Tokenizer<'a> {
type Item = Result<Token, TokenizerError>; type Item = Result<Token, TokenizerError>;
fn next(&mut self) -> Option<Result<Token, TokenizerError>> { fn next(&mut self) -> Option<Result<Token, TokenizerError>> {
let Some(c) = self.0.next() else { let c = self.0.next()?;
return None;
};
match c { match c {
'0'..='9' => { '0'..='9' => {
let mut num = String::from(c); let mut num = String::from(c);
@ -75,7 +73,7 @@ impl<'a> Iterator for Tokenizer<'a> {
} }
'a'..='z' => { 'a'..='z' => {
let mut ident = String::from(c); let mut ident = String::from(c);
while let Some(c @ 'a'..='z' | c @ '_' | c @ '0'..='9') = self.0.peek() { while let Some(c @ ('a'..='z' | '_' | '0'..='9')) = self.0.peek() {
ident.push(*c); ident.push(*c);
self.0.next(); self.0.next();
} }
@ -104,9 +102,7 @@ fn parse(input: &str) -> Result<Expression, ParserError> {
let mut tokens = tokenize(input); let mut tokens = tokenize(input);
fn parse_expr<'a>(tokens: &mut Tokenizer<'a>) -> Result<Expression, ParserError> { fn parse_expr<'a>(tokens: &mut Tokenizer<'a>) -> Result<Expression, ParserError> {
let Some(tok) = tokens.next().transpose()? else { let tok = tokens.next().ok_or(ParserError::UnexpectedEOF)??;
return Err(ParserError::UnexpectedEOF);
};
let expr = match tok { let expr = match tok {
Token::Number(num) => { Token::Number(num) => {
let v = num.parse()?; let v = num.parse()?;
@ -148,9 +144,7 @@ impl<'a> Iterator for Tokenizer<'a> {
type Item = Token; type Item = Token;
fn next(&mut self) -> Option<Token> { fn next(&mut self) -> Option<Token> {
let Some(c) = self.0.next() else { let c = self.0.next()?;
return None;
};
match c { match c {
'0'..='9' => { '0'..='9' => {
let mut num = String::from(c); let mut num = String::from(c);
@ -162,7 +156,7 @@ impl<'a> Iterator for Tokenizer<'a> {
} }
'a'..='z' => { 'a'..='z' => {
let mut ident = String::from(c); let mut ident = String::from(c);
while let Some(c @ 'a'..='z' | c @ '_' | c @ '0'..='9') = self.0.peek() { while let Some(c @ ('a'..='z' | '_' | '0'..='9')) = self.0.peek() {
ident.push(*c); ident.push(*c);
self.0.next(); self.0.next();
} }