episode 15

Author: Byron

Cargo.lock

@@ -1,2 +1,2 @@
 [workspace]
-members = ["./ownership-and-borrowing", "options-and-results", "errors", "iterators", "strings", "boxing", "conversions"]
+members = ["./ownership-and-borrowing", "options-and-results", "errors", "iterators", "strings", "boxing", "conversions", "closures"]

Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "closures"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

closures/Cargo.toml

@@ -0,0 +1,56 @@
+#![allow(dead_code)]
+
+use std::ops::AddAssign;
+
+fn main() {
+    println!("{:?}", map("a", |v| v));
+    println!("{:?}", map(4, |v| v + 1));
+    fn add_one(v: u32) -> u32 {
+        v + 1
+    }
+    println!("{:?}", map(4, add_one));
+    println!(
+        "{:?}",
+        map("a".to_string(), |mut v| {
+            v.push_str("hello");
+            v
+        })
+    );
+
+    let mut count = 0;
+    println!(
+        "{:?}",
+        map("a".to_string(), move |mut v| {
+            count += 1;
+            v.push_str("hello");
+            v
+        })
+    );
+    dbg!(count);
+
+    struct Closure<'a> {
+        count: &'a mut u32,
+    }
+    impl<'a> Closure<'a> {
+        fn call(&mut self) -> u32 {
+            self.count.add_assign(1);
+            *self.count
+        }
+    }
+}
+struct Iter<F> {
+    map: F,
+}
+
+impl<F> Iter<F>
+where
+    F: FnMut(u32) -> u32,
+{
+    fn next(&mut self) -> u32 {
+        (self.map)(42)
+    }
+}
+fn map<T>(item: T, mut f: impl FnMut(T) -> T) -> T {
+    let t = f(item);
+    f(t)
+}