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Parse parenthesized expressions

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Tiffany Bennett 2016-08-02 22:12:22 -04:00
parent 15228a373b
commit 5d861c9d32
1 changed files with 11 additions and 1 deletions
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12
src/unit_defs.rs
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@ -21,6 +21,8 @@ pub enum Token {
RBrack,
LBrace,
RBrace,
LPar,
RPar,
Plus,
Minus,
Error(String),
@ -49,6 +51,8 @@ impl<'a> Iterator for TokenIterator<'a> {
']' => Token::RBrack,
'{' => Token::LBrace,
'}' => Token::RBrace,
'(' => Token::LPar,
')' => Token::RPar,
'+' => Token::Plus,
'-' => Token::Minus,
'/' => match self.0.peek() {
@ -171,6 +175,7 @@ fn parse_term(mut iter: &mut Iter) -> Expr {
Token::Number(num) => Expr::Const(num),
Token::Plus => Expr::Plus(Box::new(parse_term(iter))),
Token::Minus => Expr::Neg(Box::new(parse_term(iter))),
Token::LPar => parse_expr(iter),
x => Expr::Error(format!("Expected term, got {:?}", x))
}
}
@ -190,7 +195,8 @@ fn parse_pow(mut iter: &mut Iter) -> Expr {
fn parse_mul(mut iter: &mut Iter) -> Expr {
let mut terms = vec![parse_pow(iter)];
loop { match *iter.peek().unwrap() {
Token::Slash | Token::TriplePipe | Token::Newline | Token::Comment | Token::Eof => break,
Token::Slash | Token::TriplePipe | Token::RPar | Token::Newline | Token::Comment |
Token::Eof => break,
_ => terms.push(parse_pow(iter))
}}
if terms.len() == 1 {
@ -208,6 +214,10 @@ pub fn parse_expr(mut iter: &mut Iter) -> Expr {
iter.next();
terms.push(parse_mul(iter));
},
Token::RPar => {
iter.next();
break
},
Token::TriplePipe | Token::Newline | Token::Comment | Token::Eof | _ => break,
} }
terms.into_iter().fold(left, |a, b| Expr::Frac(Box::new(a), Box::new(b)))