From a1fc1827121d3c313b21fe04c02f543d827f321d Mon Sep 17 00:00:00 2001
From: Andrew Johnson <andrewjohnson@Andrews-MacBook-Pro.local>
Date: Thu, 24 May 2018 18:47:25 -0600
Subject: [PATCH] debugging result

---
 Chapter09/.gitignore          |  1 +
 Chapter09/Cargo.toml          |  4 +++
 Chapter09/debugging_result.rs | 50 +++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+)
 create mode 100644 Chapter09/.gitignore
 create mode 100644 Chapter09/debugging_result.rs

diff --git a/Chapter09/.gitignore b/Chapter09/.gitignore
new file mode 100644
index 0000000..b881d2f
--- /dev/null
+++ b/Chapter09/.gitignore
@@ -0,0 +1 @@
+data.txt
diff --git a/Chapter09/Cargo.toml b/Chapter09/Cargo.toml
index fec0c89..562f5b3 100644
--- a/Chapter09/Cargo.toml
+++ b/Chapter09/Cargo.toml
@@ -67,3 +67,7 @@ path = "performance_exponential.rs"
 [[bin]]
 name = "performance_reference"
 path = "performance_reference.rs"
+
+[[bin]]
+name = "debugging_result"
+path = "debugging_result.rs"
diff --git a/Chapter09/debugging_result.rs b/Chapter09/debugging_result.rs
new file mode 100644
index 0000000..e0cfbb2
--- /dev/null
+++ b/Chapter09/debugging_result.rs
@@ -0,0 +1,50 @@
+fn expect_1or2or_other(n: u64) -> Option<u64> {
+   match n {
+     1|2 => Some(n),
+     _ => None
+   }
+}
+
+fn expect_1or2or_error(n: u64) -> Result<u64,()> {
+   match n {
+     1|2 => Ok(n),
+     _ => Err(())
+   }
+}
+
+fn mixed_1or2() -> Result<(),()> {
+   expect_1or2or_other(1);
+   expect_1or2or_other(2);
+   expect_1or2or_other(3);
+
+   expect_1or2or_error(1)?;
+   expect_1or2or_error(2)?;
+   expect_1or2or_error(3).unwrap_or(222);
+
+   Ok(())
+}
+
+use std::fs::File;
+use std::io::prelude::*;
+use std::io;
+
+fn lots_of_io() -> io::Result<()> {
+   {
+      let mut file = File::create("data.txt")?;
+      file.write_all(b"data\ndata\ndata")?;
+   }
+   {
+      let mut file = File::open("data.txt")?;
+      let mut data = String::new();
+      file.read_to_string(&mut data)?;
+      println!("{}", data);
+   }
+
+   Ok(())
+}
+
+fn main() {
+   mixed_1or2().expect("mixed 1 or 2 is OK.");
+
+   lots_of_io().expect("lots of io is OK.");
+}