functions, loops & user input

Author: hitesh-bhatnagar

examples/01_variables.rs

@@ -50,8 +50,8 @@ fn main() {
 
     // PART5 : Constants
 
-    const euler_num: f32 = 2.71828;
-    println!("Max euler_num= {}", euler_num );
+    const EULER_NUM: f32 = 2.71828;
+    println!("Max euler_num= {}", EULER_NUM );
 
 
 

examples/02_functions.rs

@@ -0,0 +1,111 @@
+// TO RUN THE FILE : cargo run --example 02_functions
+// use std::io;
+use std::io::{self, Write};
+
+fn add(x: i32, y: i32) -> i32{
+    x+y         // NOTE : In rust no ; means return 
+}
+
+fn prod(x: i32, y: i32) -> i32{
+    return x*y; // can work as well
+}
+
+fn grade (score : u32) -> &'static str{ // refers to a reference where the borrowed data is valid for the entire duration of the running program
+    match score {
+        90..=100 => "A",
+        80..=89 => "B",
+        70..=79 => "C",
+        60..=69 => "D",
+        _ => "F",
+    }
+}
+
+fn main() -> io::Result<()>{            // this is for safety so that program do not panic
+    println!("add(5,3) = {}", add(5, 3));
+    println!("prod(5,3) = {}", prod(5, 3));
+    println!("grade(95) = {}", grade(95));
+    
+    // Conditional expression
+    let number = 67;
+    
+    if number > 5{
+        println!("{} is greater than 5", number);
+    }else{
+        println!("{} is less than 5 ", number);
+    }
+    
+    // In Rust you can assign if/else value to a variable
+    let message = if number > 5{"big"} else {"small"};
+    println!("Number is {}", message);
+    
+    // Loops
+    let mut count = 0;
+    let result = loop {
+        count += 1;
+        if count == 5{
+            break count*2;
+        }
+    };
+    
+    println!("Loop result = {}", result);
+    
+    count = 0;
+    while count <5{
+        count += 1;
+        
+    }
+    println!("While loop result = {}", count);
+    
+    count = 0;
+    for i in 0..=5 {
+        count += i;
+    }
+    println!("For loop result = {}", count);
+    
+    // MATCH
+    
+    let cmd = "echo";
+    match cmd {
+        "quit" => println!("Exiting"),
+        "help" => println!("help"),
+        "echo" => println!("Hello world"),
+        _ => println!("Unknown cmd"),
+        
+    }
+    
+//  MATCH can be used inside a variable     
+    let code = 404;
+    let meaning = match code {
+        200 => "OK",
+        404 => "Not Found",
+        500 => "Server Error",
+        _ => "Unknown",
+    };
+    println!("HTTP {} : {}", code, meaning);
+    
+    println!("Score 95 = grade {}", grade(95));
+    println!("Score 83 = grade {}", grade(83));
+    println!("Score 60 = grade {}", grade(60));
+    
+    
+    // PART 5 : Reading user input
+    println!("Type a command (echo / help / exit");
+    
+    let mut input = String::new();
+    io::stdout().flush()?;  // ensures the prompt apprears before the program waits for input
+    io::stdin().read_line(&mut input)?;
+    
+    input= input.trim().to_string();
+    
+    if input.is_empty(){
+        println!("Please enter a command");
+    } else {
+        match input.as_str() {      // when matching against 'input' use as_str() to ensure the type is correct
+            "echo" => println!("Hello world "),
+            "help" => println!("Available commands : echo, help, exit"),
+            "quit" => println!("Exiting ..."),
+            other => println!("Unknown Command: {}", other),
+        }
+    }
+    Ok(())
+}

examples/03_ownership_and_borrowing.rs

@@ -0,0 +1,7 @@
+use std::io;
+
+fn main() -> io::Result<()>{
+    
+    
+    Ok(())
+}