Merge pull request #280 from sjmann/generics-exercises

feat: added generics exercises
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fmoko 2020-04-05 14:40:34 +02:00 committed by GitHub
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### Generics
In this section you'll learn about saving yourself many lines of code with generics!
### Book Sections
- [Generic Data Types](https://doc.rust-lang.org/stable/book/ch10-01-syntax.html)

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// This shopping list program isn't compiling!
// Use your knowledge of generics to fix it.
// I AM NOT DONE
fn main() {
let mut shopping_list: Vec<?> = Vec::new();
shopping_list.push("milk");
}

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// This powerful wrapper provides the ability to store a positive integer value.
// Rewrite it using generics so that it supports wrapping ANY type.
// I AM NOT DONE
struct Wrapper<u32> {
value: u32
}
impl<u32> Wrapper<u32> {
pub fn new(value: u32) -> Self {
Wrapper { value }
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn store_u32_in_wrapper() {
assert_eq!(Wrapper::new(42).value, 42);
}
#[test]
fn store_str_in_wrapper() {
// TODO: Delete this assert and uncomment the one below once you have finished the exercise.
assert!(false);
// assert_eq!(Wrapper::new("Foo").value, "Foo");
}
}

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// An imaginary magical school has a new report card generation system written in rust!
// Currently the system only supports creating report cards where the student's grade
// is represented numerically (e.g. 1.0 -> 5.5). However, the school also issues alphabetical grades
// (A+ -> F-) and needs to be able to print both types of report card!
// Make the necessary code changes to support alphabetical report cards, thereby making the second
// test pass.
// I AM NOT DONE
pub struct ReportCard {
pub grade: f32,
pub student_name: String,
pub student_age: u8,
}
impl ReportCard {
pub fn print(&self) -> String {
format!("{} ({}) - achieved a grade of {}", &self.student_name, &self.student_age, &self.grade)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn generate_numeric_report_card() {
let report_card = ReportCard {
grade: 2.1,
student_name: "Tom Wriggle".to_string(),
student_age: 12,
};
assert_eq!(report_card.print(), "Tom Wriggle (12) - achieved a grade of 2.1");
}
#[test]
fn generate_alphabetic_report_card() {
// TODO: Make sure to change the grade here after you finish the exercise.
let report_card = ReportCard {
grade: 2.1,
student_name: "Gary Plotter".to_string(),
student_age: 11,
};
assert_eq!(report_card.print(), "Gary Plotter (11) - achieved a grade of A+");
}
}

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@ -624,6 +624,38 @@ Try mutating the incoming string vector.
Vectors provide suitable methods for adding an element at the end. See Vectors provide suitable methods for adding an element at the end. See
the documentation at: https://doc.rust-lang.org/std/vec/struct.Vec.html""" the documentation at: https://doc.rust-lang.org/std/vec/struct.Vec.html"""
# Generics
[[exercises]]
name = "generics1"
path = "exercises/generics/generics1.rs"
mode = "compile"
hint = """
Vectors in rust make use of generics to create dynamically sized arrays of any type.
You need to tell the compiler what type we are pushing onto this vector."""
[[exercises]]
name = "generics2"
path = "exercises/generics/generics2.rs"
mode = "test"
hint = """
Think carefully about what we need to do here. Currently we are wrapping only values of
type 'u32'. Maybe we need to update the explicit references to this data type somehow?
"""
[[exercises]]
name = "generics3"
path = "exercises/generics/generics3.rs"
mode = "test"
hint = """
To find the best solution to this challenge you're going to need to think back to your
knowledge of traits, specifically Trait Bound Syntax - you may also need this: "use std::fmt::Display;"
This is definitely harder than the last two exercises! You need to think about not only making the
ReportCard struct generic, but also the correct property - you will need to change the implementation
of the struct slightly too...you can do it!
"""
# THREADS # THREADS
[[exercises]] [[exercises]]