From 7e8ee5ed9cad6484e9f13f81731b102ced58402e Mon Sep 17 00:00:00 2001
From: Adam Carpenter <gitlab@53hor.net>
Date: Tue, 9 Jul 2019 15:14:04 -0400
Subject: Init.
---
rust-book/functional/src/main.rs | 188 +++++++++++++++++++++++++++++++++++++++
1 file changed, 188 insertions(+)
create mode 100755 rust-book/functional/src/main.rs
(limited to 'rust-book/functional/src')
diff --git a/rust-book/functional/src/main.rs b/rust-book/functional/src/main.rs
new file mode 100755
index 0000000..7749e58
--- /dev/null
+++ b/rust-book/functional/src/main.rs
@@ -0,0 +1,188 @@
+//use std::thread;
+//use std::time::Duration;
+//
+//struct Cacher<T>
+// where T: Fn(u32) -> u32
+//{
+// calculation: T,
+// value: Option<u32>,
+//}
+//
+//impl<T> Cacher<T>
+// where T: Fn(u32) -> u32
+//{
+// fn new (calculation: T) -> Cacher<T> {
+// Cacher {
+// calculation,
+// value: None,
+// }
+// }
+//
+// fn value(&mut self, arg: u32) -> u32 {
+// match self.value {
+// Some(v) => v,
+// None => {
+// let v = (self.calculation)(arg);
+// self.value = Some(v);
+// v
+// },
+// }
+// }
+//}
+//
+//fn main() {
+// let simulated_user_specified_value = 26;
+// let simulated_random_number = 3;
+//
+// generate_workout(
+// simulated_user_specified_value,
+// simulated_random_number
+// );
+//}
+//
+//fn generate_workout(intensity: u32, random_number: u32) {
+// let mut expensive_result = Cacher::new(|num| {
+// println!("calculating slowly...");
+// thread::sleep(Duration::from_secs(2));
+// num
+// });
+//
+// if intensity < 25 {
+// println!(
+// "Today, do {} pushups!",
+// expensive_result.value(intensity)
+// );
+// println!(
+// "Next, do {} situps!",
+// expensive_result.value(intensity)
+// );
+// }
+// else {
+// if random_number == 3 {
+// println!("Take a break today! Remember to stay hydrated!");
+// }
+// else {
+// println!(
+// "Today, run for {} minutes!",
+// expensive_result.value(intensity)
+// );
+// }
+// }
+//}
+//
+
+
+
+
+fn main() {
+ let v1 = vec![1, 2, 3];
+ let v1_iter = v1.iter();
+
+ for val in v1_iter {
+ dbg!(val);
+ }
+}
+
+#[test]
+fn iterator_demonstration() {
+ let v1 = vec![1, 2, 3];
+ let mut v1_iter = v1.iter();
+
+ assert_eq!(v1_iter.next(), Some(&1));
+ assert_eq!(v1_iter.next(), Some(&2));
+ assert_eq!(v1_iter.next(), Some(&3));
+ assert_eq!(v1_iter.next(), None);
+}
+
+#[test]
+fn iterator_sum() {
+ let v1 = vec![1, 2, 3];
+ let v1_iter = v1.iter();
+ let total: i32 = v1_iter.sum();
+ assert_eq!(total, 6);
+}
+
+#[test]
+fn iterator_map() {
+ let v1: Vec<i32> = vec![1, 2, 3];
+ let v2: Vec<_> = v1.iter().map(|x| x + 1).collect();
+ assert_eq!(v2, vec![2, 3, 4]);
+}
+
+
+
+#[derive(PartialEq, Debug)]
+struct Shoe {
+ size: i32,
+ style: String,
+}
+
+fn shoes_in_my_size(shoes: Vec<Shoe>, shoe_size: i32) -> Vec<Shoe> {
+ shoes.into_iter()
+ .filter(|s| s.size == shoe_size)
+ .collect()
+}
+
+#[test]
+fn filters_by_size() {
+ let shoes = vec![
+ Shoe { size: 10, style: String::from("sneaker") },
+ Shoe { size: 10, style: String::from("boot") },
+ Shoe { size: 13, style: String::from("sandal") },
+ ];
+
+ let in_my_size = shoes_in_my_size(shoes, 10);
+
+ assert_eq!(
+ in_my_size,
+ vec![
+ Shoe { size: 10, style: String::from("sneaker") },
+ Shoe { size: 10, style: String::from("boot") },
+ ]
+ );
+}
+
+struct Counter {
+ count: u32,
+}
+
+impl Counter {
+ fn new() -> Counter {
+ Counter { count: 0 }
+ }
+}
+
+impl Iterator for Counter {
+ type Item = u32;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ self.count += 1;
+
+ if self.count < 6 {
+ Some(self.count)
+ }
+ else {
+ None
+ }
+ }
+}
+
+#[test]
+fn calling_next_directly() {
+ let mut counter = Counter::new();
+ assert_eq!(counter.next(), Some(1));
+ assert_eq!(counter.next(), Some(2));
+ assert_eq!(counter.next(), Some(3));
+ assert_eq!(counter.next(), Some(4));
+ assert_eq!(counter.next(), Some(5));
+ assert_eq!(counter.next(), None);
+}
+
+#[test]
+fn using_other_iterator_trait_methods() {
+ let sum: u32 = Counter::new().zip(Counter::new().skip(1))
+ .map(|(a, b)| a * b)
+ .filter(|x| x % 3 == 0)
+ .sum();
+ assert_eq!(18, sum);
+}
--
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