added demos, shuflr example

Author: BartMassey

README.md

@@ -59,3 +59,6 @@ in a controlled repository now.
 * `lifetimes-example.rs`: example involving Rust lifetimes
 * `strref.rs`: example involving Rust string clones and copies
 * `closures/`: closure examples
+* `for-demo.rs`: example of passing iterators
+* `iter-from-fn.rs`: example use of `iter::from_fn()`
+* `rev.rs`: example `for` loop with reversed iterator

for-demo.rs

@@ -0,0 +1,17 @@
+pub fn count<T, E>(values: T)
+    where T: IntoIterator<Item=E>, E: std::fmt::Debug
+{
+    let mut iter = values.into_iter();
+    while let Some(i) = iter.next() {
+        println!("{i:?}");
+    }
+}
+
+fn main() {
+    count(1..=5);
+    count('a'..='c');
+    count(["hello", "world"]);
+    let v = vec![(1, 2), (3, 4)];
+    count(v.iter());
+    count(v.iter());
+}

iter-from-fn.rs

@@ -0,0 +1,13 @@
+fn main() {
+    let mut c = 'a';
+    let iter = std::iter::from_fn(|| {
+        if c >= 'e' {
+            return None;
+        }
+        let result = c;
+        c = std::char::from_u32(c as u32 + 1).unwrap();
+        Some(result)
+    });
+    let xs: String = iter.collect();
+    println!("{xs}");
+}

rev.rs

@@ -0,0 +1,8 @@
+fn main() {
+    for i in 0..3 {
+        println!("{i}");
+    }
+    for i in (0..3).rev() {
+        println!("{i}");
+    }
+}

shuflr/Cargo.toml

@@ -12,3 +12,7 @@ rand = "0.8.3"
 [lib]
 name = "shuflr"
 path = "shuflr.rs"
+
+[[example]]
+name = "demo"
+path = "demo.rs"

shuflr/demo.rs

@@ -0,0 +1,11 @@
+use shuflr::*;
+use rand::thread_rng;
+
+fn main() {
+    let v: Vec<char> = ('a'..='z').collect();
+    let s: String = v
+        .shuffled(&mut thread_rng())
+        .flat_map(|c| c.to_uppercase())
+        .collect();
+    println!("{s}");
+}