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authorNerdyPepper <[email protected]>2019-03-19 16:32:45 +0000
committerNerdyPepper <[email protected]>2019-03-19 16:32:45 +0000
commit7375d87ea553bc318b224909544dbda470de73ca (patch)
tree6fab37a88e4f3003fe3c9ba1035eed7f7ff5f65d /src/main.rs
parent2f74f994b96012889c3b6f6e53369045a04da533 (diff)
add lexed to rpn function
Diffstat (limited to 'src/main.rs')
-rw-r--r--src/main.rs70
1 files changed, 66 insertions, 4 deletions
diff --git a/src/main.rs b/src/main.rs
index c91b662..d9f6b01 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,7 +6,7 @@ pub struct Operator {
6 is_left_associative: bool, 6 is_left_associative: bool,
7} 7}
8 8
9#[derive(Debug)] 9#[derive(Debug, Copy, Clone)]
10pub enum Token { 10pub enum Token {
11 Operator(Operator), 11 Operator(Operator),
12 Num(f64), 12 Num(f64),
@@ -31,11 +31,11 @@ impl Operator {
31} 31}
32 32
33fn main() { 33fn main() {
34 let input = "1(2)"; 34 let input = "1 + 2 * 3";
35 let input = input.replace(" ", ""); 35 let input = input.replace(" ", "");
36 let lexed = lexer(&input); 36 let lexed = lexer(&input);
37 println!("{:?}", lexed); 37 let postfixed = to_postfix(lexed.unwrap());
38 println!("{}", lexed.unwrap().len()); 38 println!("{:?}", postfixed);
39} 39}
40 40
41fn lexer(input: &str) -> Result<Vec<Token>, String> { 41fn lexer(input: &str) -> Result<Vec<Token>, String> {
@@ -93,3 +93,65 @@ fn lexer(input: &str) -> Result<Vec<Token>, String> {
93 } 93 }
94 Ok(result) 94 Ok(result)
95} 95}
96
97fn to_postfix(tokens: Vec<Token>) -> Result<Vec<Token>, String> {
98 let mut postfixed: Vec<Token> = vec![];
99 let mut op_stack: Vec<Token> = vec![];
100 for token in tokens {
101 match token {
102 Token::Num(_) => {
103 postfixed.push(token);
104 println!("pushed a number {:?}", token);
105 },
106 Token::Operator(current_op) => {
107 while let Some(top_op) = op_stack.last() {
108 match top_op {
109 Token::LParen => {
110 return Err(format!("Mismatched Parentheses!"))
111 }
112 Token::Operator(top_op) => {
113 let tp = top_op.precedence;
114 let cp = current_op.precedence;
115 if tp > cp || (tp == cp && top_op.is_left_associative) {
116 postfixed.push(op_stack.pop().unwrap());
117 println!("pushed an operator special {:?}", token);
118 } else {
119 break;
120 }
121 }
122 _ => {
123 return Err(format!("Unexpected match branch part 2"))
124 }
125 }
126 }
127 op_stack.push(token);
128 println!("pushed an operator {:?}", token);
129 },
130 Token::LParen => {
131 op_stack.push(token);
132 },
133 Token::RParen => {
134 let mut found: bool = false;
135 while let Some(top_op) = op_stack.last() {
136 match top_op {
137 Token::LParen => {
138 let _ = op_stack.pop().unwrap();
139 found = true;
140 },
141 _ => {
142 postfixed.push(op_stack.pop().unwrap());
143 }
144 }
145 }
146 if found == false {
147 return Err(format!("Mismatched parentheses part 2"))
148 }
149 }
150
151 }
152 }
153 while let Some(op) = op_stack.pop() {
154 postfixed.push(op);
155 }
156 Ok(postfixed)
157}