From 8d471f3d0e9887785962ad5b6f728905954dd857 Mon Sep 17 00:00:00 2001
From: Benjamin Saunders <ben.e.saunders@gmail.com>
Date: Tue, 21 Jan 2020 22:36:02 -0800
Subject: [PATCH] Illustrate alternative structure in beep example

---
 examples/beep.rs | 41 +++++++++++++++++++++--------------------
 1 file changed, 21 insertions(+), 20 deletions(-)

diff --git a/examples/beep.rs b/examples/beep.rs
index 6405467..9df4f2b 100644
--- a/examples/beep.rs
+++ b/examples/beep.rs
@@ -9,8 +9,22 @@ fn main() -> Result<(), anyhow::Error> {
         .default_output_device()
         .expect("failed to find a default output device");
     let format = device.default_output_format()?;
-    let sample_rate = format.sample_rate.0 as f32;
-    let channels = format.channels as usize;
+
+    match format.data_type {
+        cpal::SampleFormat::F32 => run::<f32>(&device, &format.shape())?,
+        cpal::SampleFormat::I16 => run::<i16>(&device, &format.shape())?,
+        cpal::SampleFormat::U16 => run::<u16>(&device, &format.shape())?,
+    }
+
+    Ok(())
+}
+
+fn run<T>(device: &cpal::Device, shape: &cpal::Shape) -> Result<(), anyhow::Error>
+where
+    T: cpal::Sample,
+{
+    let sample_rate = shape.sample_rate.0 as f32;
+    let channels = shape.channels as usize;
 
     // Produce a sinusoid of maximum amplitude.
     let mut sample_clock = 0f32;
@@ -21,24 +35,11 @@ fn main() -> Result<(), anyhow::Error> {
 
     let err_fn = |err| eprintln!("an error occurred on stream: {}", err);
 
-    let stream = match format.data_type {
-        cpal::SampleFormat::F32 => device.build_output_stream(
-            &format.shape(),
-            move |data: &mut [f32]| write_data(data, channels, &mut next_value),
-            err_fn,
-        )?,
-        cpal::SampleFormat::I16 => device.build_output_stream(
-            &format.shape(),
-            move |data: &mut [i16]| write_data(data, channels, &mut next_value),
-            err_fn,
-        )?,
-        cpal::SampleFormat::U16 => device.build_output_stream(
-            &format.shape(),
-            move |data: &mut [u16]| write_data(data, channels, &mut next_value),
-            err_fn,
-        )?,
-    };
-
+    let stream = device.build_output_stream(
+        shape,
+        move |data: &mut [T]| write_data(data, channels, &mut next_value),
+        err_fn,
+    )?;
     stream.play()?;
 
     std::thread::sleep(std::time::Duration::from_millis(1000));