From a050178c692c59861cb0fb9666321fbef7578039 Mon Sep 17 00:00:00 2001
From: NerdyPepper <akshayoppiliappan@gmail.com>
Date: Thu, 21 Mar 2019 10:54:29 +0530
Subject: refactor into modules

---
 src/lex/mod.rs | 145 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 src/lex/mod.rs

(limited to 'src/lex/mod.rs')

diff --git a/src/lex/mod.rs b/src/lex/mod.rs
new file mode 100644
index 0000000..af5ff06
--- /dev/null
+++ b/src/lex/mod.rs
@@ -0,0 +1,145 @@
+use std::f64;
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub struct Operator {
+    token: char,
+    pub operation: fn(f64, f64) -> f64,
+    pub precedence: u8,
+    pub is_left_associative: bool,
+}
+
+impl Operator {
+    fn token_from_op(token: char, operation: fn(f64, f64) -> f64, precedence: u8, is_left_associative: bool) -> Token {
+        Token::Operator(
+            Operator {
+                token,
+                operation,
+                precedence,
+                is_left_associative
+            }
+        )
+    }
+    pub fn operate(self, x: f64, y: f64) -> f64 {
+        (self.operation)(x, y)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct Function {
+    token: String,
+    relation: fn(f64) -> f64,
+}
+
+impl Function {
+    fn token_from_fn(token: String, relation: fn(f64) -> f64) -> Token {
+        Token::Function(
+            Function {
+                token,
+                relation
+            }
+        )
+    }
+    pub fn apply(self, arg: f64) -> f64 {
+        (self.relation)(arg)
+    }
+}
+
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Token {
+    Operator(Operator),
+    Num(f64),
+    Function(Function),
+    LParen,
+    RParen
+}
+
+pub fn lexer(input: &str) -> Result<Vec<Token>, String> {
+    let mut num_vec: String = String::new();
+    let mut char_vec: String = String::new();
+    let mut result: Vec<Token> = vec![];
+    for letter in input.chars() {
+        match letter {
+            '0'...'9' | '.' => {
+                num_vec.push(letter);
+            },
+            'a'...'z' | 'A'...'Z' => {
+                let parse_num = num_vec.parse::<f64>().ok();
+                if let Some(x) = parse_num {
+                    result.push(Token::Num(x));
+                    result.push(Operator::token_from_op('*', |x, y| x * y, 3, true));
+                    num_vec.clear();
+                }
+                char_vec.push(letter);
+            },
+            '+' | '-' | '/' | '*' | '^' => {
+                let parse_num = num_vec.parse::<f64>().ok();
+                if let Some(x) = parse_num {
+                    result.push(Token::Num(x));
+                    num_vec.clear();
+                }
+                let operator_token: Token = match letter {
+                    '+' => Operator::token_from_op('+', |x, y| x + y, 2, true),
+                    '-' => Operator::token_from_op('-', |x, y| x - y, 2, true),
+                    '/' => Operator::token_from_op('/', |x, y| x / y, 3, true),
+                    '*' => Operator::token_from_op('*', |x, y| x * y, 3, true),
+                    '^' => Operator::token_from_op('^', |x, y| x.powf(y), 4, false),
+                    _ => panic!("unexpected op whuuu"),
+                };
+                result.push(operator_token);
+            },
+            '('  => {
+                if char_vec.len() > 0 {
+                    let funct = char_vec.clone();
+                    match &funct[..] {
+                        "sin" | "sine"      => result.push(Function::token_from_fn("sin".into(), |x| x.to_radians().sin())),
+                        "cos" | "cosine"    => result.push(Function::token_from_fn("cos".into(), |x| x.to_radians().cos())),
+                        "tan" | "tangent"   => result.push(Function::token_from_fn("tan".into(), |x| x.to_radians().tan())),
+                        "csc" | "cosec"     => result.push(Function::token_from_fn("csc".into(), |x| 1f64 / x.to_radians().sin())),
+                        "sec" | "secant"    => result.push(Function::token_from_fn("sec".into(), |x| 1f64 / x.to_radians().cos())),
+                        "cot" | "cotangent" => result.push(Function::token_from_fn("cot".into(), |x| 1f64 / x.to_radians().tan())),
+                        "ln"                => result.push(Function::token_from_fn("ln".into(), |x| x.ln())),
+                        "log"               => result.push(Function::token_from_fn("log".into(), |x| x.log10())),
+                        "sqrt"              => result.push(Function::token_from_fn("sqrt".into(), |x| x.sqrt())),
+                        _                   => return Err(format!("Unexpected function {}", funct))
+                    }
+                    char_vec.clear();
+                } else {
+                    let parse_num = num_vec.parse::<f64>().ok();
+                    if let Some(x) = parse_num {
+                        result.push(Token::Num(x));
+                        result.push(Operator::token_from_op('*', |x, y| x * y, 3, true));
+                        num_vec.clear();
+                    }
+                }
+
+                if let Some(x) = result.last() {
+                    match x {
+                        Token::RParen => {
+                            result.push(Operator::token_from_op('*', |x, y| x * y, 3, true));
+                        },
+                        _ => {}
+                    };
+                }
+                result.push(Token::LParen);
+            },
+            ')' => {
+                let parse_num = num_vec.parse::<f64>().ok();
+                if let Some(x) = parse_num {
+                    result.push(Token::Num(x));
+                    num_vec.clear();
+                }
+                result.push(Token::RParen);
+            }
+            ' ' => {}
+            _ => {
+                return Err(format!("Unexpected character: {}", letter))
+            }
+        }
+    }
+    let parse_num = num_vec.parse::<f64>().ok();
+    if let Some(x) = parse_num {
+        result.push(Token::Num(x));
+        num_vec.clear();
+    }
+    Ok(result)
+}
-- 
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