From 0c85dc1193978b5165491b99cc4922caf8d14a65 Mon Sep 17 00:00:00 2001
From: Abdou Seck <djily02016@gmail.com>
Date: Mon, 16 Dec 2019 08:34:30 -0500
Subject: [PATCH 1/2] feat: Add type conversion and parsing exercises
---
exercises/conversions/README.md | 20 +++++++
exercises/conversions/as_ref_mut.rs | 36 +++++++++++++
exercises/conversions/from_into.rs | 72 ++++++++++++++++++++++++++
exercises/conversions/from_str.rs | 48 +++++++++++++++++
exercises/conversions/try_from_into.rs | 70 +++++++++++++++++++++++++
exercises/conversions/using_as.rs | 16 ++++++
info.toml | 40 ++++++++++++++
7 files changed, 302 insertions(+)
create mode 100644 exercises/conversions/README.md
create mode 100644 exercises/conversions/as_ref_mut.rs
create mode 100644 exercises/conversions/from_into.rs
create mode 100644 exercises/conversions/from_str.rs
create mode 100644 exercises/conversions/try_from_into.rs
create mode 100644 exercises/conversions/using_as.rs
diff --git a/exercises/conversions/README.md b/exercises/conversions/README.md
new file mode 100644
index 00000000..114bd428
--- /dev/null
+++ b/exercises/conversions/README.md
@@ -0,0 +1,20 @@
+### Type conversions
+
+
+Rust offers a multitude of ways to convert a value of a given type into another type.
+
+The simplest form of type conversion is a type cast expression. It is denoted with the binary operator `as`. For instance, `println!("{}", 1 + 1.0);` would not compile, since `1` is an integer while `1.0` is a float. However, `println!("{}", 1 as f32 + 1.0)` should compile. The exercise [`using_as`](using_as.rs) tries to cover this.
+
+Rust also offers traits that facilitate type conversions upon implementation. These traits can be found under the [`convert`](https://doc.rust-lang.org/std/convert/index.html) module.
+The traits are the following:
+- `From` and `Into` covered in [`from_into`](from_into.rs)
+- `TryFrom` and `TryInto` covered in [`try_from_into`](try_from_into.rs)
+- `AsRef` and `AsMut` covered in [`as_ref_mut`](as_ref_mut.rs)
+
+Furthermore, the `std::str` module offers a trait called [`FromStr`](https://doc.rust-lang.org/std/str/trait.FromStr.html) which helps with converting strings into target types via the `parse` method on strings. If properly implemented for a given type `Person`, then `let p: Person = "Mark,20".parse().unwrap()` should both compile and run without panicking.
+
+These should be the main ways ***within the standard library*** to convert data into your desired types.
+
+#### Book Sections
+
+These are not directly covered in the book, but the standard library has great documentation for [conversions here](https://doc.rust-lang.org/std/convert/index.html). The `FromStr` trait is also covered [here](https://doc.rust-lang.org/std/str/trait.FromStr.html).
\ No newline at end of file
diff --git a/exercises/conversions/as_ref_mut.rs b/exercises/conversions/as_ref_mut.rs
new file mode 100644
index 00000000..9d92fff6
--- /dev/null
+++ b/exercises/conversions/as_ref_mut.rs
@@ -0,0 +1,36 @@
+// AsRef and AsMut allow for cheap reference-to-reference conversions.
+// Read more about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html
+// and https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
+
+// Obtain the number of bytes (not characters) in the given argument
+// Add the AsRef trait appropriately as a trait bound
+fn byte_counter<T>(arg: T) -> usize {
+ arg.as_ref().as_bytes().len()
+}
+
+// Obtain the number of characters (not bytes) in the given argument
+// Add the AsRef trait appropriately as a trait bound
+fn char_counter<T>(arg: T) -> usize {
+ arg.as_ref().chars().collect::<Vec<_>>().len()
+}
+
+fn main() {
+ let s = "Café au lait";
+ println!("{}", char_counter(s));
+ println!("{}", byte_counter(s));
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn different_counts() {
+ let s = "Café au lait";
+ assert_ne!(char_counter(s), byte_counter(s));
+ }
+ fn same_counts() {
+ let s = "Cafe au lait";
+ assert_eq!(char_counter(s), byte_counter(s));
+ }
+}
\ No newline at end of file
diff --git a/exercises/conversions/from_into.rs b/exercises/conversions/from_into.rs
new file mode 100644
index 00000000..c988ee8d
--- /dev/null
+++ b/exercises/conversions/from_into.rs
@@ -0,0 +1,72 @@
+// The From trait is used for value-to-value conversions.
+// If From is implemented correctly for a type, the Into trait should work conversely.
+// You can read more about it at https://doc.rust-lang.org/std/convert/trait.From.html
+#[derive(Debug)]
+struct Person {
+ name: String,
+ age: usize,
+}
+
+// We implement the Default trait to use it as a fallback
+// when the provided string is not convertible into a Person object
+impl Default for Person {
+ fn default() -> Person {
+ Person {
+ name: String::from("John"),
+ age: 30,
+ }
+ }
+}
+
+// Your task is to complete this implementation
+// in order for the line `let p = Person::from("Mark,20")` to compile
+// Please note that you'll need to parse the age component into a `usize`
+// with something like `"4".parse::<usize>()`. The outcome of this needs to
+// be handled appropriately.
+//
+// Steps:
+// 1. If the length of the provided string is 0, then return the default of Person
+// 2. Split the given string on the commas present in it
+// 3. Extract the first element from the split operation and use it as the name
+// 4. Extract the other element from the split operation and parse it into a `usize` as the age
+// If while parsing the age, something goes wrong, then return the default of Person
+// Otherwise, then return an instantiated Person onject with the results
+impl From<&str> for Person {
+ fn from(s: &str) -> Person {
+ }
+}
+
+fn main() {
+ // Use the `from` function
+ let p1 = Person::from("Mark,20");
+ // Since From is implemented for Person, we should be able to use Into
+ let p2: Person = "Gerald,70".into();
+ println!("{:?}", p1);
+ println!("{:?}", p2);
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+ #[test]
+ fn test_default() {
+ // Test that the default person is 30 year old John
+ let dp = Person::default();
+ assert_eq!(dp.name, "John");
+ assert_eq!(dp.age, 30);
+ }
+ #[test]
+ fn test_bad_convert() {
+ // Test that John is returned when bad string is provided
+ let p = Person::from("");
+ assert_eq!(p.name, "John");
+ assert_eq!(p.age, 30);
+ }
+ #[test]
+ fn test_good_convert() {
+ // Test that "Mark,20" works
+ let p = Person::from("Mark,20");
+ assert_eq!(p.name, "Mark");
+ assert_eq!(p.age, 20);
+ }
+}
diff --git a/exercises/conversions/from_str.rs b/exercises/conversions/from_str.rs
new file mode 100644
index 00000000..247ae143
--- /dev/null
+++ b/exercises/conversions/from_str.rs
@@ -0,0 +1,48 @@
+// This does practically the same thing that TryFrom<&str> does.
+// Additionally, upon implementing FromStr, you can use the `parse` method
+// on strings to generate an object of the implementor type.
+// You can read more about it at https://doc.rust-lang.org/std/str/trait.FromStr.html
+use std::str::FromStr;
+
+#[derive(Debug)]
+struct Person {
+ name: String,
+ age: usize,
+}
+
+// Steps:
+// 1. If the length of the provided string is 0, then return an error
+// 2. Split the given string on the commas present in it
+// 3. Extract the first element from the split operation and use it as the name
+// 4. Extract the other element from the split operation and parse it into a `usize` as the age
+// If while parsing the age, something goes wrong, then return an error
+// Otherwise, then return a Result of a Person object
+impl FromStr for Person {
+ type Err = String;
+ fn from_str(s: &str) -> Result<Person, Self::Err> {
+ }
+}
+
+fn main() {
+ let p = "Mark,20".parse::<Person>().unwrap();
+ println!("{:?}", p);
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn empty_input() {
+ assert!("".parse::<Person>().is_err());
+ }
+ #[test]
+ fn good_input() {
+ assert!("John,32".parse::<Person>().is_ok());
+ }
+ #[test]
+ #[should_panic]
+ fn missing_age() {
+ "John".parse::<Person>().unwrap();
+ }
+}
\ No newline at end of file
diff --git a/exercises/conversions/try_from_into.rs b/exercises/conversions/try_from_into.rs
new file mode 100644
index 00000000..ff77089a
--- /dev/null
+++ b/exercises/conversions/try_from_into.rs
@@ -0,0 +1,70 @@
+// TryFrom is a simple and safe type conversion that may fail in a controlled way under some circumstances.
+// Basically, this is the same as From. The main difference is that this should return a Result type
+// instead of the target type itself.
+// You can read more about it at https://doc.rust-lang.org/std/convert/trait.TryFrom.html
+use std::convert::{TryInto, TryFrom};
+
+#[derive(Debug)]
+struct Person {
+ name: String,
+ age: usize,
+}
+
+// Your task is to complete this implementation
+// in order for the line `let p = Person::try_from("Mark,20")` to compile
+// and return an Ok result of inner type Person.
+// Please note that you'll need to parse the age component into a `usize`
+// with something like `"4".parse::<usize>()`. The outcome of this needs to
+// be handled appropriately.
+//
+// Steps:
+// 1. If the length of the provided string is 0, then return an error
+// 2. Split the given string on the commas present in it
+// 3. Extract the first element from the split operation and use it as the name
+// 4. Extract the other element from the split operation and parse it into a `usize` as the age
+// If while parsing the age, something goes wrong, then return an error
+// Otherwise, then return a Result of a Person object
+impl TryFrom<&str> for Person {
+ type Error = String;
+ fn try_from(s: &str) -> Result<Self, Self::Error> {
+ }
+}
+
+fn main() {
+ // Use the `from` function
+ let p1 = Person::try_from("Mark,20");
+ // Since From is implemented for Person, we should be able to use Into
+ let p2: Result<Person, _> = "Gerald,70".try_into();
+ println!("{:?}", p1);
+ println!("{:?}", p2);
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+ #[test]
+ fn test_bad_convert() {
+ // Test that John is returned when bad string is provided
+ let p = Person::try_from("");
+ assert!(p.is_err());
+ }
+ #[test]
+ fn test_good_convert() {
+ // Test that "Mark,20" works
+ let p = Person::try_from("Mark,20");
+ assert!(p.is_ok());
+ let p = p.unwrap();
+ assert_eq!(p.name, "Mark");
+ assert_eq!(p.age, 20);
+ }
+ #[test]
+ #[should_panic]
+ fn test_panic_empty_input() {
+ let p: Person = "".try_into().unwrap();
+ }
+ #[test]
+ #[should_panic]
+ fn test_panic_bad_age() {
+ let p = Person::try_from("Mark,twenty").unwrap();
+ }
+}
\ No newline at end of file
diff --git a/exercises/conversions/using_as.rs b/exercises/conversions/using_as.rs
new file mode 100644
index 00000000..37eb69f2
--- /dev/null
+++ b/exercises/conversions/using_as.rs
@@ -0,0 +1,16 @@
+// Type casting in Rust is done via the usage of the `as` operator.
+// Please note that the `as` operator is not only used when type casting.
+// It also helps with renaming imports.
+
+// The goal is to make sure that the division does not fail to compile
+fn average(values: &[f64]) -> f64 {
+ let total = values
+ .iter()
+ .fold(0.0, |a, b| a + b);
+ total / values.len()
+}
+
+fn main() {
+ let values = [3.5, 0.3, 13.0, 11.7];
+ println!("{}", average(&values));
+}
\ No newline at end of file
diff --git a/info.toml b/info.toml
index 99628d18..3ca1824b 100644
--- a/info.toml
+++ b/info.toml
@@ -610,3 +610,43 @@ answers and don't understand why they work and yours doesn't.
If you've learned from the sample solutions, I encourage you to come
back to this exercise and try it again in a few days to reinforce
what you've learned :)"""
+
+# TYPE CONVERSIONS
+
+[[exercises]]
+name = "using_as"
+path = "exercises/conversions/using_as.rs"
+mode = "compile"
+hint = """
+Use the `as` operator to cast one of the operands in the last line of the
+`average` function into the expected return type."""
+
+[[exercises]]
+name = "from_into"
+path = "exercises/conversions/from_into.rs"
+mode = "test"
+hint = """
+Follow the steps provided right before the `From` implementation"""
+
+[[exercises]]
+name = "try_from_into"
+path = "exercises/conversions/try_from_into.rs"
+mode = "test"
+hint = """
+Follow the steps provided right before the `From` implementation.
+You can also use the example at https://doc.rust-lang.org/std/convert/trait.TryFrom.html"""
+
+[[exercises]]
+name = "as_ref_mut"
+path = "exercises/conversions/as_ref_mut.rs"
+mode = "test"
+hint = """
+Add AsRef<str> as a trait bound to the functions."""
+
+[[exercises]]
+name = "from_str"
+path = "exercises/conversions/from_str.rs"
+mode = "test"
+hint = """
+If you've already solved try_from_into.rs, then this is almost a copy-paste.
+Otherwise, go ahead and solve try_from_into.rs first."""
\ No newline at end of file
From fc26b5e151b985ff5e369b3ef4049c0b01f11b0c Mon Sep 17 00:00:00 2001
From: Abdou Seck <djily02016@gmail.com>
Date: Mon, 16 Dec 2019 11:33:00 -0500
Subject: [PATCH 2/2] I AM NOT DONE comment in conversions exercise files
---
exercises/conversions/as_ref_mut.rs | 2 ++
exercises/conversions/from_into.rs | 1 +
exercises/conversions/from_str.rs | 1 +
exercises/conversions/try_from_into.rs | 1 +
exercises/conversions/using_as.rs | 1 +
5 files changed, 6 insertions(+)
diff --git a/exercises/conversions/as_ref_mut.rs b/exercises/conversions/as_ref_mut.rs
index 9d92fff6..8a907031 100644
--- a/exercises/conversions/as_ref_mut.rs
+++ b/exercises/conversions/as_ref_mut.rs
@@ -2,12 +2,14 @@
// Read more about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html
// and https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
+// I AM NOT DONE
// Obtain the number of bytes (not characters) in the given argument
// Add the AsRef trait appropriately as a trait bound
fn byte_counter<T>(arg: T) -> usize {
arg.as_ref().as_bytes().len()
}
+// I AM NOT DONE
// Obtain the number of characters (not bytes) in the given argument
// Add the AsRef trait appropriately as a trait bound
fn char_counter<T>(arg: T) -> usize {
diff --git a/exercises/conversions/from_into.rs b/exercises/conversions/from_into.rs
index c988ee8d..666f234b 100644
--- a/exercises/conversions/from_into.rs
+++ b/exercises/conversions/from_into.rs
@@ -18,6 +18,7 @@ impl Default for Person {
}
}
+// I AM NOT DONE
// Your task is to complete this implementation
// in order for the line `let p = Person::from("Mark,20")` to compile
// Please note that you'll need to parse the age component into a `usize`
diff --git a/exercises/conversions/from_str.rs b/exercises/conversions/from_str.rs
index 247ae143..3c889d73 100644
--- a/exercises/conversions/from_str.rs
+++ b/exercises/conversions/from_str.rs
@@ -10,6 +10,7 @@ struct Person {
age: usize,
}
+// I AM NOT DONE
// Steps:
// 1. If the length of the provided string is 0, then return an error
// 2. Split the given string on the commas present in it
diff --git a/exercises/conversions/try_from_into.rs b/exercises/conversions/try_from_into.rs
index ff77089a..255d2e1f 100644
--- a/exercises/conversions/try_from_into.rs
+++ b/exercises/conversions/try_from_into.rs
@@ -10,6 +10,7 @@ struct Person {
age: usize,
}
+// I AM NOT DONE
// Your task is to complete this implementation
// in order for the line `let p = Person::try_from("Mark,20")` to compile
// and return an Ok result of inner type Person.
diff --git a/exercises/conversions/using_as.rs b/exercises/conversions/using_as.rs
index 37eb69f2..54f96515 100644
--- a/exercises/conversions/using_as.rs
+++ b/exercises/conversions/using_as.rs
@@ -2,6 +2,7 @@
// Please note that the `as` operator is not only used when type casting.
// It also helps with renaming imports.
+// I AM NOT DONE
// The goal is to make sure that the division does not fail to compile
fn average(values: &[f64]) -> f64 {
let total = values