Kuis 3 | Faisal Affan

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// This quiz tests:
// - Generics
// - Traits
//
// 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 in the struct `ReportCard` and the impl
// block to support alphabetical report cards in addition to numerical ones.

// TODO: Adjust the struct as described above.
struct ReportCard {
    grade: f32,
    student_name: String,
    student_age: u8,
}

// TODO: Adjust the impl block as described above.
impl ReportCard {
    fn print(&self) -> String {
        format!(
            "{} ({}) - achieved a grade of {}",
            &self.student_name, &self.student_age, &self.grade,
        )
    }
}

fn main() {
    // You can optionally experiment here.
}

#[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() {
        let report_card = ReportCard {
            grade: "A+",
            student_name: "Gary Plotter".to_string(),
            student_age: 11,
        };
        assert_eq!(
            report_card.print(),
            "Gary Plotter (11) - achieved a grade of A+",
        );
    }
}

Dalam kuis ini kita ditugaskan untuk menyesuaikan ReportCard dan implementasinya untuk menerima grade teks dan grade float.
Kita dapat menggunakan generics untuk ini.
Pertama kita perlu mengubah struct ReportCard sehingga akan menerima tipe generik untuk field grade seperti ini:
```
struct ReportCard<T> {
    grade: T,
    student_name: String,
    student_age: u8,
}
```

Kemudian kita sesuaikan implementasinya untuk menerima generics juga seperti ini:

impl<T> ReportCard<T> {
    fn print(&self) -> String {
        format!(
            "{} ({}) - achieved a grade of {}",
            &self.student_name, &self.student_age, &self.grade,
        )
    }
}

Tapi kita masih memiliki beberapa error di bawah saat mengompilasi.
```
error[E0277]: `T` doesn't implement `std::fmt::Display`
```
Ini karena format! membutuhkan trait tertentu.

Jadi kita dapat menambahkan trait std::fmt::Display ke dalam sintaks impl kita seperti ini:

impl<T: std::fmt::Display> ReportCard<T> {
    fn print(&self) -> String {
        format!(
            "{} ({}) - achieved a grade of {}",
            &self.student_name, &self.student_age, &self.grade,
        )
    }
}

Dalam kuis ini compiler Rust sangat berguna, ia dapat menyarankan trait apa yang harus ditambahkan dalam sintaks impl.