Add errors exercise

exercise/errors/Cargo.toml

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+[package]
+name = "aquarium"
+version = "0.1.0"
+authors = ["Nathan Stocks <nathan@agileperception.com>"]
+edition = "2018"
+
+[dependencies]
+# I thought you might want this for your library...
+thiserror = "1.0"
+# ...and this for your binary
+anyhow = "1.0"

exercise/errors/src/lib.rs

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+// 1. Create error type(s) representing the following three conditions:
+// - An orca is hungry (Hungry)
+// - An orca is too young (TooYoung)
+// - The orca's name is too long (LongName)
+//
+// As a reminder, here are the 5 Guidelines for creating an error type
+// (1) Use an `enum` for your error type
+// (2) Your error conditions should be enum variants grouped in as few enums as makes sense
+// (3) Don't expose error types other than your own to users
+// (4) Make your enum non-exhaustive
+// (5) Implement the Debug, Display, and Error traits
+// (5b) You can use thiserror's `Error` macro to derive Display and Error.h
+//
+// Once you have completed the error type correctly, you should be able to run `cargo build --lib`
+// without any errors.
+
+// pub enum OrcaError...
+
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+#[non_exhaustive]
+pub enum OrcaError {
+    #[error("I'm too hungry to do that.")]
+    Hungry,
+    #[error("I'm too young to do that.")]
+    TooYoung,
+    #[error("I would, but my name is just so long!")]
+    LongName,
+}
+
+pub struct Orca {
+    pub name: String,
+    pub age: u8,
+    pub hungry: bool,
+}
+
+impl Orca {
+    pub fn say_your_name(&self) -> Result<String, OrcaError> {
+        if self.name.len() > 10 {
+            Err(OrcaError::LongName)
+        } else {
+            Ok(format!("Hi, my name is {} and I'm an Orca!", self.name))
+        }
+    }
+    pub fn flip(&self) -> Result<String, OrcaError> {
+        if self.age < 4 {
+            Err(OrcaError::TooYoung)
+        } else {
+            Ok(format!("Yippee, I'm doing a flip!"))
+        }
+    }
+    pub fn shake_hands(&self) -> Result<String, OrcaError> {
+        if self.hungry {
+            Err(OrcaError::Hungry)
+        } else {
+            Ok(format!("Nice to meet you, let's shake hands!"))
+        }
+    }
+}

exercise/errors/src/main.rs

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+// START IN lib.rs!
+
+use aquarium::Orca;
+
+// (You already did #1 in lib.rs, right?)
+// 2a. Uncomment and finish the play_time function below
+// - Bring anyhow::Result into scope with a `use` statement
+// - Have the function return a Result<Vec<String>>. The vector of Strings will represent successful
+//   outcomes of various performances.
+
+// fn play_time(orca: &Orca) -> ... {
+//     let mut responses = vec![];
+//     // 2b. There are three methods on the Orca struct:
+//     // - .say_your_name()
+//     // - .flip()
+//     // - .shake_hands()
+//     //
+//     // For each of the three methods above:
+//     // - Call the method on `orca`, using the `?` operator to unwrap the value / return the error
+//     // - Push the unwrapped string onto the `responses` vector using the .push() method
+
+//     // let response = ...    // this can be done with an intermediate variable...
+//     // responses.push( ... ) // ...or all on one line. Either way is fine!
+
+//     Ok(responses)
+// }
+
+fn main() {
+    let orcas = vec![
+        Orca {
+            name: "Augustinius".into(),
+            age: 7,
+            hungry: false,
+        },
+        Orca {
+            name: "Bitty".into(),
+            age: 2,
+            hungry: true,
+        },
+        Orca {
+            name: "Carson".into(),
+            age: 5,
+            hungry: true,
+        },
+        Orca {
+            name: "Devin".into(),
+            age: 6,
+            hungry: false,
+        },
+    ];
+    for orca in &orcas {
+        match play_time(orca) {
+            Ok(responses) => {
+                println!("{} did a FABULOUS PERFORMANCE!", orca.name);
+                for response in responses {
+                    println!("  {}", response);
+                }
+            }
+            Err(e) => println!("{} can't perform today: {}", orca.name, e.to_string()),
+        }
+    }
+}