Add CLI example

examples/cli/platform/src/lib.rs

@@ -0,0 +1,52 @@
+use roc_std::RocCallResult;
+use roc_std::RocList;
+use std::time::SystemTime;
+
+extern "C" {
+    #[link_name = "roc__mainForHost_1_exposed"]
+    fn quicksort(list: RocList<i64>, output: &mut RocCallResult<RocList<i64>>) -> ();
+}
+
+const NUM_NUMS: usize = 100;
+
+#[no_mangle]
+pub fn rust_main() -> isize {
+    let nums: RocList<i64> = {
+        let mut nums = Vec::with_capacity(NUM_NUMS);
+
+        for index in 0..nums.capacity() {
+            let num = index as i64 % 12;
+
+            nums.push(num);
+        }
+
+        RocList::from_slice(&nums)
+    };
+
+    println!("Running Roc quicksort on {} numbers...", nums.len());
+    let start_time = SystemTime::now();
+    let answer = unsafe {
+        use std::mem::MaybeUninit;
+        let mut output = MaybeUninit::uninit();
+
+        quicksort(nums, &mut *output.as_mut_ptr());
+
+        match output.assume_init().into() {
+            Ok(value) => value,
+            Err(msg) => panic!("roc failed with message {}", msg),
+        }
+    };
+
+    let end_time = SystemTime::now();
+    let duration = end_time.duration_since(start_time).unwrap();
+
+    println!(
+        "Roc quicksort took {:.4} ms to compute this answer: {:?}",
+        duration.as_secs_f64() * 1000.0,
+        // truncate the answer, so stdout is not swamped
+        &answer.as_slice()[0..20]
+    );
+
+    // Exit code
+    0
+}