added strings

Author: hitesh-bhatnagar

examples/09_strings.rs

@@ -18,7 +18,7 @@ fn main(){
 	// convert String --> &str
 	let owned = String::from("hello");
 	let borrowed : &str = &owned;		// borrow it as &str
-	prontln!("borrowed: {}", borrowed);
+	println!("borrowed: {}", borrowed);
 
 	// PART 2: Building Strings
 
@@ -29,21 +29,21 @@ fn main(){
 
 	// push --> append a single character
 	s.push('!');
-	println!("{}", S);
+	println!("{}", s);
 
 	// + operator --> concatenates
 	// NOTE: Consumes first string!!
 	let s1 = String::from("Is this a real life ");
 	let s2 = String::from("or just fantasy ");
 
-	let s3 = s1+s2;		// s1 is MOVED here --> can't use s1 after this
+	let s3 = s1 + &s2;		// s1 is MOVED here --> can't use s1 after this
 
 	println!("{}", s3);
 
 	// format! macro --> joins w/o consuming (most flexible)
 	let first = String::from("Caught in a landscape, ");
 	let sec = String::from("no escape from reality");
-	let combined = format!("{} {}!", first, second);
+	let combined = format!("{} {}!", first, sec);
 
 	println!("{}", combined);		//NOTE: first & sec are still valid -- format! borrows them
 
@@ -73,15 +73,91 @@ fn main(){
 
     // find --> returns the index of first match, or None
     match s.find("Rust") {
-    	Some(i) => println!("'Rust' found at index {}", i);
-    	None => println!("not found");
+    	Some(i) => println!("'Rust' found at index {}", i),
+    	None => println!("not found"),
     }
 
     // PART 5 : Replacing
 
     let s = String::from("I love Java and Java was my first programming language");
 
     // replace --> replaces ALL occurences
-	
+	let replaced = s.replace("Java", "Rust");
+	println!("{}", replaced);
+
+	// replacen --> replaces only N occurrences
+	let replaced_once = s.replacen("Java", "Rust", 1);
+	println!("{}", replaced_once);		
+
+	// PART 6 : Splitting --> most important for CLI tools
+
+	let sentence = "hello world foo bar";
+
+	let words: Vec<&str> = sentence.split(' ').collect();
+	println!("split: {:?}", words);
+
+	// splitn --> split into AT MOST n parts
+	// Very useful for parsing commands like "SET key value"
+	let cmd = "SET my key some value with spaces";
+	let parts: Vec<&str> = cmd.splitn(3, ' ').collect();
+	println!("splitn(3): {:?}", parts);
+	// ["SET", "my", "key some value with spaces"]
+	// NOTICE: everything after the 2nd space stays together
+
+	// split and check first word
+	let input = "echo hello world";
+	let mut parts = input.splitn(2, ' ');
+	let command = parts.next().unwrap_or("");
+	let args = parts.next().unwrap_or("");
+
+	println!("command: '{}', args: '{}'", command, args);
+
+	// PART 7: Case Conversion
+
+	let s = "Hello Universe";
+	println!("converted to lowercase: {}", s.to_lowercase());
+	println!("converted to uppercase: {}", s.to_uppercase());
+
+	// PART 8: Parsing --> converting strings to other types
+	let num: i32 = "42".parse().unwrap();
+	println!("parsed i32: {}", num);
+
+	let float: f64 = "3.14".parse().unwrap();
+	println!("parsed f64: {}", float);
+
+	// Handle parse failure safely
+	match "abc".parse::<i32>() {
+		Ok(n) => println!("parsed: {}", n),
+		Err(e) => println!("parse failed: {}", e),
 
+	}	
+
+	//number --> string
+	let n = 42;
+	let s = n.to_string();
+	println!("number to string: {}", s);
+
+	// PART 9: Joining
+
+	let words = vec!["It's", "Rust Lang", "baby"];
+
+	// join --> connect items with a separator
+	let sentence = words.join(" ");
+	println!("{}", sentence);
+
+	let csv = words.join(",");
+	println!("{}", csv);
+
+	// PART 10: Characters
+
+	let s = String::from("hello");
+	for i in s.chars() {
+		print!("{} ", i);
+	}
+	println!();
+
+	// Count characters
+	let char_count = s.chars().count();
+	println!("char count: {}", char_count);
+	
 }