mod word_utils;
+mod lib;
use std::collections::HashMap;
+use std::io::{prelude::*, ErrorKind};
+use std::fs::{self, File};
+use lib::*;
use word_utils::{first_word, second_word};
fn test_strings() {
println!("scores after doubling: {:?}", scores);
// double scores of immutable hashmap (rebuild it)
- let collect_scores: HashMap<_, _> = collect_scores.iter()
+ let collect_scores: HashMap<_, _> = collect_scores.into_iter()
.map(|(k, v)| (k, 2 * v))
.collect();
println!("collect_scores after rebuilding with doubling: {:?}", collect_scores);
}
+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)
+ }
+}
+
+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 test_closures() {
+ let mut expensive_int_result = Cacher::new(|x| {
+ println!("calculating expensive int result for {}", x);
+ 2 * x
+ });
+
+ println!("1st int call for value 1: {}", expensive_int_result.value(1));
+ println!("2nd int call for value 1: {}", expensive_int_result.value(1));
+ println!("1st int call for value 2: {}", expensive_int_result.value(2));
+
+ let mut expensive_str_result = Cacher::new(|x: &str| {
+ println!("calculating expensive str result for {}", x);
+ x.len()
+ });
+
+ println!("1st int call for value abc: {}", expensive_str_result.value("abc"));
+ println!("2nd int call for value abc: {}", expensive_str_result.value("abc"));
+ println!("1st int call for value defg: {}", expensive_str_result.value("defg"));
+}
+
fn main() {
test_strings();
test_vectors();
test_hashmaps();
+ test_files();
+ test_generics();
+ test_closures();
}