1 files changed, 24 insertions, 8 deletions
diff --git a/gcd.rs b/gcd.rs
index 95cc865..0925368 100644
--- a/gcd.rs
+++ b/gcd.rs
@@ -1,7 +1,17 @@
-use std::env;
+// Synopsis:
+//
+// $ rustc gcd.rs -o gcd-rs
+// $ ./gcd-rs 11 22 33 121
+// 11
+//
 
-fn gcd2(mut a: u64, mut b: u64) -> u64 {
-    while b != 0 {
+use std::{cmp, env, ops};
+
+fn gcd2<T>(mut a: T, mut b: T) -> T
+where
+    T: cmp::PartialEq + Copy + ops::Rem<Output = T> + ops::Neg<Output = T>,
+{
+    while b != -b {
         let c = b;
         b = a % b;
         a = c;
@@ -10,11 +20,17 @@ fn gcd2(mut a: u64, mut b: u64) -> u64 {
     a
 }
 
-fn main() {
-    // XXX skip(1) to skip program name:
-    let nums = env::args().skip(1).map(|s| s.parse().unwrap());
+fn gcdn<T>(nums: impl IntoIterator<Item = T>) -> Option<T>
+where
+    T: cmp::PartialEq + Copy + ops::Rem<Output = T> + ops::Neg<Output = T>,
+{
+    nums.into_iter().reduce(gcd2)
+}
 
-    let gcd = nums.fold(0, gcd2);
+fn main() {
+    let nums = env::args().skip(1).map(|s| s.parse::<i64>().unwrap());
 
-    println!("{}", gcd);
+    if let Some(gcd) = gcdn(nums) {
+        println!("{gcd}");
+    }
 }