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78 lines
2.8 KiB
Rust
78 lines
2.8 KiB
Rust
// An imaginary magical school has a new report card generation system written
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// in Rust! Currently, the system only supports creating report cards where the
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// student's grade is represented numerically (e.g. 1.0 -> 5.5). However, the
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// school also issues alphabetical grades (A+ -> F-) and needs to be able to
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// print both types of report card!
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//
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// Make the necessary code changes in the struct `ReportCard` and the impl
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// block to support alphabetical report cards in addition to numerical ones.
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use std::fmt::Display;
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// Make the struct generic over `T`.
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//
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// Note: We could also add the Display trait bound here at the struct level, i.e.,
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// `struct ReportCard<T: Display> { ... }`. That would enforce that every `ReportCard` instance
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// must have a grade that is displayable. However, by not placing the bound here, we allow
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// the creation of `ReportCard` instances with non-displayable grades (but then we cannot use the `print` method).
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// Since the main purpose of this struct is to be printable, it would also be reasonable to add the bound at the struct level.
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// In this solution, we choose to put the bound only in the `impl` block to show that we can conditionally
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// implement methods only when the type satisfies certain traits. This offers more flexibility in some advanced scenarios.
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struct ReportCard<T> {
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// ^^^
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grade: T,
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// ^
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student_name: String,
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student_age: u8,
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}
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// To be able to print the grade, it has to implement the `Display` trait.
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//
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// Note: We implement the `print` method only for `ReportCard<T>` where `T` implements `Display`.
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// This means that if we have a `ReportCard` with a grade that doesn't implement `Display`,
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// we can still create the instance, but we cannot call the `print` method on it.
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impl<T: Display> ReportCard<T> {
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// ^^^^^^^ require that `T` implements `Display`.
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fn print(&self) -> String {
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format!(
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"{} ({}) - achieved a grade of {}",
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&self.student_name, &self.student_age, &self.grade,
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)
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}
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}
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fn main() {
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// You can optionally experiment here.
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn generate_numeric_report_card() {
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let report_card = ReportCard {
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grade: 2.1,
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student_name: "Tom Wriggle".to_string(),
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student_age: 12,
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};
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assert_eq!(
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report_card.print(),
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"Tom Wriggle (12) - achieved a grade of 2.1",
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);
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}
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#[test]
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fn generate_alphabetic_report_card() {
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let report_card = ReportCard {
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grade: "A+",
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student_name: "Gary Plotter".to_string(),
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student_age: 11,
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};
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assert_eq!(
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report_card.print(),
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"Gary Plotter (11) - achieved a grade of A+",
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);
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}
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}
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