lr -> pr

pr/ch2/gcd/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "gcd"
+version = "0.1.0"
+authors = ["Kyle Isom <kyle@imap.cc>"]
+
+[dependencies]

pr/ch2/gcd/src/main.rs

@@ -0,0 +1,43 @@
+use std::io::Write;
+use std::str::FromStr;
+
+fn gcd(mut n: u64, mut m: u64) -> u64 {
+    assert!(n != 0 && m != 0);
+    while m != 0 {
+        if m < n {
+            let t = m;
+            m = n;
+            n = t;
+        }
+        m = m % n;
+    }
+    n
+}
+
+#[test]
+fn test_gcd() {
+    assert_eq!(gcd(14, 15), 1);
+    assert_eq!(gcd(2 * 3 * 5 * 11 * 17,
+                   3 * 7 * 11 * 13 * 19),
+               3 * 11);
+}
+
+fn main() {
+    let mut numbers = Vec::new();
+
+    for arg in std::env::args().skip(1) {
+        numbers.push(u64::from_str(&arg).expect("error parsing argument as u64"));
+    }
+
+    if numbers.len() == 0 {
+        writeln!(std::io::stderr(), "Usage: gcd NUMBER...").unwrap();
+        std::process::exit(1);
+    }
+
+    let mut d = numbers[0];
+    for m in &numbers[1..] {
+        d = gcd(d, *m);
+    }
+    
+    println!("The greatest common divisor of {:?} is {}", numbers, d);
+}