.gitignore

@@ -0,0 +1 @@
+rust-calc/target

rust-calc/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "rust-calc"
+version = "0.1.0"

rust-calc/Cargo.toml

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+[package]
+name = "rust-calc"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

rust-calc/src/main.rs

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+use std::{
+    ops::{AddAssign, DivAssign, MulAssign, SubAssign},
+    process,
+};
+
+// Provide a conformable way to work with symbols
+#[derive(Clone, Debug)]
+enum Symbol {
+    Minus,
+    Plus,
+    Multiply,
+    Divide,
+
+    OpenBracket,
+    CloseBracket,
+}
+impl Symbol {
+    // Checks if the given symbol has priority or not
+    fn priority(&self) -> bool {
+        match self {
+            Symbol::Multiply => true,
+            Symbol::Divide => true,
+
+            _ => false,
+        }
+    }
+    // Check if it brackets (open or close)
+    fn bracket(&self) -> bool {
+        match self {
+            Symbol::OpenBracket => true,
+            Symbol::CloseBracket => true,
+
+            _ => false,
+        }
+    }
+    // Check if it's an open bracket
+    fn open_bracket(&self) -> bool {
+        match self {
+            Symbol::OpenBracket => true,
+
+            _ => false,
+        }
+    }
+    // Check if it's an close bracket
+    fn close_bracket(&self) -> bool {
+        match self {
+            Symbol::CloseBracket => true,
+
+            _ => false,
+        }
+    }
+}
+
+// Provides a object to hold the number being parsed from the string
+struct TmpNum {
+    s: String,
+}
+impl TmpNum {
+    // Simple constructor
+    pub fn new() -> Self {
+        Self { s: String::new() }
+    }
+    // Add a new char to the list of chars used to describe the number in a base 10 fashion
+    fn push(&mut self, c: char) {
+        self.s.push(c);
+    }
+    // Returns the float number from the parsed input
+    fn get(&mut self) -> f64 {
+        let n = self.s.parse::<f64>().ok().expect("number is malformed");
+        self.s = String::new();
+
+        n
+    }
+    // Returns the length of the current save number as chars.
+    fn len(&self) -> usize {
+        self.s.len()
+    }
+}
+
+// Takes as argument a string representing the wanted calculation and return a list of symbols and values.
+fn parse(pattern: String) -> (Vec<Symbol>, Vec<f64>) {
+    let mut symbols = Vec::new();
+    let mut numbers = Vec::new();
+
+    let mut number = TmpNum::new();
+
+    // Iteration of the chars
+    let mut i = 0;
+    while i < pattern.len() {
+        let c = pattern.chars().nth(i).expect("some char");
+        // Check if the given char is a recognized symbol
+        let s: Option<Symbol> = match c {
+            '-' => Some(Symbol::Minus),
+            '+' => Some(Symbol::Plus),
+            '*' => Some(Symbol::Multiply),
+            'x' => Some(Symbol::Multiply), // This is the second way to express multiplication
+            '/' => Some(Symbol::Divide),
+
+            '(' => Some(Symbol::OpenBracket),
+            ')' => Some(Symbol::CloseBracket),
+
+            _ => None,
+        };
+
+        match s {
+            // If the char is a recognized symbol
+            Some(s) => {
+                // If the char is a bracket
+                if s.bracket() {
+                    // Keep track of the number of brackets
+                    let mut nb_bracket = 1;
+                    // Keep track of the new position into the list
+                    let mut i2 = i + 1;
+                    // Loop the rest of the input
+                    while i2 < pattern.len() {
+                        let c2 = pattern.chars().nth(i2).expect("some char");
+                        // Recognize the brackets from the rest of the input
+                        let s2: Option<Symbol> = match c2 {
+                            '(' => Some(Symbol::OpenBracket),
+                            ')' => Some(Symbol::CloseBracket),
+
+                            _ => None,
+                        };
+                        match s2 {
+                            // If brackets
+                            Some(s2) => {
+                                // If open add the increment
+                                if s2.open_bracket() {
+                                    nb_bracket += 1;
+                                    // If close decrease the counter and check if it gets to zero
+                                } else if s2.close_bracket() {
+                                    nb_bracket -= 1;
+                                    if nb_bracket == 0 {
+                                        // Save the content of the brackets
+                                        let new_pattern = pattern
+                                            .get(i..i2)
+                                            .expect("expect the sub string")
+                                            .to_string();
+                                        // Send it to the parse function
+                                        let (tmp_symbols, tmp_numbers) = parse(new_pattern);
+                                        // Do the calculation
+                                        let tmp_result = calculation(tmp_symbols, tmp_numbers);
+                                        // Add the calculated value to the list of numbers
+                                        numbers.push(tmp_result);
+                                        // Change the position in the list
+                                        i = i2;
+
+                                        // Check the symbol after the closing bracket
+                                        let c3 = match pattern.chars().nth(i2 + 1){
+                                            Some(c) => c,
+                                            None => break,
+                                        };
+                                        if !c3.is_numeric() {
+                                            let s2 = match c3 {
+                                                '-' => Some(Symbol::Minus),
+                                                '+' => Some(Symbol::Plus),
+                                                '*' => Some(Symbol::Multiply),
+                                                '/' => Some(Symbol::Divide),
+
+                                                _ => None,
+                                            };
+                                            match s2 {
+                                                Some(s2) => {
+                                                    symbols.push(s2);
+                                                    i += 1;
+                                                }
+                                                // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                                                // This will be used in case of bracket directly followed by number.
+                                                None => {
+                                                    symbols.push(Symbol::Multiply);
+                                                }
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                            // Not a bracket, do nothing
+                            None => {}
+                        }
+                        // Add counter at the end of the loop
+                        i2 += 1;
+                    }
+                    // If not a bracket but symbol
+                } else {
+                    // If the length of number is zero, add to the current char to number
+                    // It's in the case of signed numbers
+                    if number.s.len() == 0 {
+                        number.push(c);
+                        // Otherwise add the number and the symbol
+                    } else {
+                        symbols.push(s);
+                        numbers.push(number.get());
+                    }
+                }
+            }
+            None => {
+                // It's not a recognized symbol so it must be part of a number
+                number.push(c);
+            }
+        }
+
+        // Increment the list position
+        i += 1;
+    }
+
+    // At the end the last number need to be added too.
+    if number.len() != 0 {
+        numbers.push(number.get());
+    }
+
+    // Return the values
+    (symbols, numbers)
+}
+
+// Run the calculation based on the 2 different lists of symbols and numbers
+fn calculation(symbols: Vec<Symbol>, numbers: Vec<f64>) -> f64 {
+    let mut counter = 0;
+    let mut n1 = *numbers.get(0).expect("expect at least the first value");
+
+    // Iterate the list of symbols
+
+    while counter < symbols.len() {
+        let s = symbols
+            .get(counter)
+            .expect("expect at least a symbol value");
+        let mut n2 = *numbers
+            .get(counter + 1)
+            .expect("expect at least a second value");
+
+        // If the symbol has priority then simply do the calculation and update n1
+        if s.priority() {
+            match s {
+                Symbol::Multiply => {
+                    n1.mul_assign(n2);
+                }
+                Symbol::Divide => {
+                    n1.div_assign(n2);
+                }
+                _ => {}
+            };
+        } else {
+            // Check the next symbol
+            let next_s = symbols.get(counter + 1);
+            match next_s {
+                Some(ss) => {
+                    // If the next has priority start to check until where the priority calculation goes
+                    if ss.priority() {
+                        let mut counter_2 = counter + 1;
+                        let mut nn1 = *numbers
+                            .get(counter_2)
+                            .expect("during the priority, we expect at least the first value");
+                        while counter_2 < symbols.len() {
+                            let nn2 = *numbers
+                                .get(counter_2 + 1)
+                                .expect("during the priority, we expect at least the second value");
+
+                            if ss.priority() {
+                                match ss {
+                                    Symbol::Multiply => {
+                                        nn1.mul_assign(nn2);
+                                    }
+                                    Symbol::Divide => {
+                                        nn1.div_assign(nn2);
+                                    }
+                                    _ => {}
+                                }
+                                // End of the priority.
+                                // Change the position in the list, save the new value as n1 and stop the priority loop
+                            } else {
+                                counter = counter_2;
+                                n2 = nn1;
+                                break;
+                            }
+                            n2 = nn1;
+
+                            // Increment the position in the list
+                            counter_2 += 1;
+                            counter = counter_2;
+                        }
+                    }
+                }
+                None => {}
+            }
+
+            // Run the non prioritized calculation
+            match s {
+                Symbol::Minus => {
+                    n1.sub_assign(n2);
+                }
+                Symbol::Plus => {
+                    n1.add_assign(n2);
+                }
+                _ => {}
+            }
+        }
+
+        counter += 1;
+    }
+
+    n1
+}
+
+fn main() {
+    let pattern = match std::env::args().nth(1) {
+        None => {
+            println!("Input must be provided");
+            process::exit(1)
+        }
+        Some(s) => s,
+    };
+
+    let (symbols, numbers) = parse(pattern);
+
+    // println!("{:?}", symbols);
+    // println!("{:?}", numbers);
+
+    if symbols.len() < 1 || symbols.len() + 1 != numbers.len() {
+        println!(
+            "The input is malformed {} {} {}",
+            symbols.len() < 1,
+            symbols.len() + 1 != numbers.len(),
+            symbols.len()
+        );
+        process::exit(2);
+    }
+
+    let res = calculation(symbols, numbers);
+    println!("{res}");
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{calculation, parse};
+
+    #[test]
+    fn basics() {
+        let (s, n) = parse("2+2".to_string());
+
+        assert_eq!(calculation(s, n), 4.0);
+        let (s, n) = parse("4-9".to_string());
+        assert_eq!(calculation(s, n), -5.0);
+        let (s, n) = parse("7*3".to_string());
+        assert_eq!(calculation(s, n), 21.0);
+        let (s, n) = parse("9/3".to_string());
+        assert_eq!(calculation(s, n), 3.0);
+
+        let (s, n) = parse("15*20".to_string());
+        assert_ne!(calculation(s, n), 0.0);
+    }
+
+    #[test]
+    fn signs_2() {
+        let (s, n) = parse("2*4+4".to_string());
+        assert_eq!(calculation(s, n), 12.0);
+        let (s, n) = parse("2+2*4".to_string());
+        assert_eq!(calculation(s, n), 10.0);
+        let (s, n) = parse("30/4-9".to_string());
+        assert_eq!(calculation(s, n), -1.5);
+    }
+
+    #[test]
+    fn negative_number() {
+        let (s, n) = parse("-2*4+4".to_string());
+        assert_eq!(calculation(s, n), -4.0);
+        let (s, n) = parse("-2+2*4".to_string());
+        assert_eq!(calculation(s, n), 6.0);
+    }
+
+    #[test]
+    fn with_1_bracket_set() {
+        let (s, n) = parse("2*(4+4)*2".to_string());
+        assert_eq!(calculation(s, n), 32.0);
+        let (s, n) = parse("2*(4+4)".to_string());
+        assert_eq!(calculation(s, n), 16.0);
+        let (s, n) = parse("-2*(4+4)".to_string());
+        assert_eq!(calculation(s, n), -16.0);
+        let (s, n) = parse("(4+4)*2".to_string());
+        assert_eq!(calculation(s, n), 16.0);
+    }
+}