From 7375d87ea553bc318b224909544dbda470de73ca Mon Sep 17 00:00:00 2001
From: NerdyPepper <akshayoppiliappan@gmail.com>
Date: Tue, 19 Mar 2019 22:02:45 +0530
Subject: add lexed to rpn function

---
 src/main.rs | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 66 insertions(+), 4 deletions(-)

(limited to 'src')

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 {
     is_left_associative: bool,
 }
 
-#[derive(Debug)]
+#[derive(Debug, Copy, Clone)]
 pub enum Token {
     Operator(Operator),
     Num(f64),
@@ -31,11 +31,11 @@ impl Operator {
 }
 
 fn main() {
-    let input = "1(2)";
+    let input = "1 + 2 * 3";
     let input = input.replace(" ", "");
     let lexed = lexer(&input);
-    println!("{:?}", lexed);
-    println!("{}", lexed.unwrap().len());
+    let postfixed = to_postfix(lexed.unwrap());
+    println!("{:?}", postfixed);
 }
 
 fn lexer(input: &str) -> Result<Vec<Token>, String> {
@@ -93,3 +93,65 @@ fn lexer(input: &str) -> Result<Vec<Token>, String> {
     }
     Ok(result)
 }
+
+fn to_postfix(tokens: Vec<Token>) -> Result<Vec<Token>, String> {
+    let mut postfixed: Vec<Token> = vec![];
+    let mut op_stack: Vec<Token> = vec![];
+    for token in tokens {
+        match token {
+            Token::Num(_) => {
+                postfixed.push(token);
+                println!("pushed a number {:?}", token);
+            },
+            Token::Operator(current_op) => {
+                while let Some(top_op) = op_stack.last() {
+                    match top_op {
+                        Token::LParen => {
+                            return Err(format!("Mismatched Parentheses!"))
+                        }
+                        Token::Operator(top_op) => {
+                            let tp = top_op.precedence;
+                            let cp = current_op.precedence;
+                            if tp > cp || (tp == cp && top_op.is_left_associative) {
+                                postfixed.push(op_stack.pop().unwrap());
+                                println!("pushed an operator special {:?}", token);
+                            } else {
+                                break;
+                            }
+                        }
+                        _ => {
+                            return Err(format!("Unexpected match branch part 2"))
+                        }
+                    }
+                }
+                op_stack.push(token);
+                println!("pushed an operator {:?}", token);
+            },
+            Token::LParen => {
+                op_stack.push(token);
+            },
+            Token::RParen => {
+                let mut found: bool = false;
+                while let Some(top_op) = op_stack.last() {
+                    match top_op {
+                        Token::LParen => {
+                            let _ = op_stack.pop().unwrap();
+                            found = true;
+                        },
+                        _ => {
+                            postfixed.push(op_stack.pop().unwrap());
+                        }
+                    }
+                }
+                if found == false {
+                    return Err(format!("Mismatched parentheses part 2"))
+                }
+            }
+
+        }
+    }
+    while let Some(op) = op_stack.pop() {
+        postfixed.push(op);
+    }
+    Ok(postfixed)
+}
-- 
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