+++ /dev/null
-mod word_utils;
-
-use std::collections::HashMap;
-use std::io::{prelude::*, ErrorKind};
-use std::fs::{self, File};
-
-use word_utils::{first_word, second_word};
-
-fn test_strings() {
- let s = String::from("Hello world");
- println!("first word: '{}'", first_word(&s));
- println!("second word: '{}'", second_word(&s).unwrap());
-
- let s2 = "hello dude blah";
- println!("second word of single: '{}'", second_word(s2).unwrap_or("(none)"));
-
- match second_word(s2) {
- Some(w) => println!("match: second word of '{}' exists: {}", s2, w),
- None => println!("match: second word of '{}' does not exist", s2),
- }
-}
-
-fn test_vectors() {
- let v1 = vec![1, 2, 3];
- println!("statically initialized vector: {:?}", v1);
-
- let mut v2: Vec<String> = Vec::new();
- v2.push("Hello".to_string());
- v2.push(String::from("world"));
- println!("dynamically built vector: {:?}", v2);
- println!("first element: {}", v2[0]);
- for el in &mut v2 {
- *el += "xx";
- }
- for el in &v2 {
- println!("{}", el);
- }
-}
-
-fn test_hashmaps() {
- let mut scores = HashMap::new();
- scores.insert("john", 10);
- scores.insert("mary", 20);
-
- println!("scores: {:?}", scores);
-
- // hash map with .collect()
- let persons = vec![("homer", 42), ("marge", 30)];
- let collect_scores: HashMap<_, _> = persons.into_iter().collect();
- println!("collect_scores: {:?}", collect_scores);
-
- for (p, s) in &collect_scores {
- println!("person {}: score {}", p, s);
- }
-
- println!("john's score: {}", scores.get("john").unwrap());
- println!("jake's score: {}", scores.get("jake").unwrap_or(&-1));
-
- // double scores
- for (_, v) in scores.iter_mut() {
- *v *= 2;
- }
- println!("scores after doubling: {:?}", scores);
-
- // double scores of immutable hashmap (rebuild it)
- let collect_scores: HashMap<_, _> = collect_scores.iter()
- .map(|(k, v)| (k, 2 * v))
- .collect();
- println!("collect_scores after rebuilding with doubling: {:?}", collect_scores);
-}
-
-fn read_file(path: &str) -> Result<String, std::io::Error> {
- let mut s = String::new();
- File::open(path)?
- .read_to_string(&mut s)?;
- Ok(s)
-}
-
-fn test_files() {
- if let Ok(mut f) = File::open("Cargo.toml") {
- let mut contents = String::new();
- match f.read_to_string(&mut contents) {
- Ok(len) => println!("successfully opened Cargo.toml: {:?}, contents {} bytes:\n{}\n----------", f, len, contents),
- Err(e) => panic!("could not read file: {:?}", e)
- }
- } else {
- println!("could not open Cargo.toml");
- }
-
- // alternative form, more specific error checking
- let mut f = File::open("Cargo.toml").unwrap_or_else(|e| {
- if e.kind() == ErrorKind::NotFound {
- println!("Cargo.toml not found, falling back to /dev/null");
- // need to return a File
- File::open("/dev/null").unwrap()
- } else {
- panic!("Could not open Cargo.toml: {:?}", e);
- }
- });
- let mut contents = String::new();
- let len = f.read_to_string(&mut contents).unwrap_or_else(|e| {
- panic!("Could not read file: {:?}", e);
- });
- println!("successfully opened Cargo.toml with unwrap_or_else: {:?}, contents {} bytes:\n{}\n----------", f, len, contents);
-
- // using the '?' operator
- match read_file("Cargo.toml") {
- Ok(s) => println!("Cargo.toml contents:\n{}\n-------------", s),
- Err(e) => println!("Could not open Cargo.toml: {:?}", e)
- }
-
- // using std API
- match fs::read_to_string("Cargo.toml") {
- Ok(s) => println!("Cargo.toml contents:\n{}\n-------------", s),
- Err(e) => println!("Could not open Cargo.toml: {:?}", e)
- }
-}
-
-// needs Copy trait, good for simple types
-fn largest<T: PartialOrd + Copy>(list: &[T]) -> T {
- let mut result = list[0];
- for &i in list {
- if i > result {
- result = i;
- }
- }
- result
-}
-
-// expensive for large strings, don't use that
-fn largest_clone<T: PartialOrd + Clone>(list: &[T]) -> T {
- let mut result = list[0].clone();
- for i in list {
- if *i > result {
- result = i.clone();
- }
- }
- result
-}
-
-// good for everything, but more expensive for simple types
-fn largest_ref<T: PartialOrd>(list: &[T]) -> &T {
- let mut result = &list[0];
- for i in list {
- if i > result {
- result = i;
- }
- }
- result
-}
-
-fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
- if x.len() > y.len() {
- x
- } else {
- y
- }
-}
-
-fn test_generics() {
- let num_list = vec![3, 42, -7, 100, 0];
- println!("largest number: {}", largest(&num_list));
- println!("num_list: {:?}", num_list);
-
- let char_list = vec!['a', 'y', 'q', 'm'];
- println!("largest char: {}", largest(&char_list));
-
- let str_list = vec!["hello", "world", "blue", "planet"];
- println!("largest str: {}", largest(&str_list));
- println!("str_list: {:?}", str_list);
-
- let string_list = vec!["aaaa".to_string(), "xxxxx".to_string(), "ffff".to_string()];
- println!("largest string (with cloning): {}", largest_clone(&string_list));
- println!("largest string (with ref): {}", largest_ref(&string_list));
- println!("string_list: {:?}", string_list);
-
- let s1 = String::from("abcd");
- let l;
- {
- let s2 = "efghi";
- l = longest(&s1, s2);
- }
- println!("longest string: {}", l);
-}
-
-fn main() {
- test_strings();
- test_vectors();
- test_hashmaps();
- test_files();
- test_generics();
-}