Project skeleton
- Rust course
- Beginner
- Lesson 25/115
- 6 min
Set up the calculator project skeleton with main and println!.
Project: a calculator
In this project you will write a command-line calculator that reads an expression like 12 * 3 from the user and prints the result. First set up the structure: reading input, parsing, computing and handling errors will live in separate functions.
fn hesapla(a: f64, op: char, b: f64) -> Result<f64, String> {
// + - * / operations
}
fn main() {
// loop: read → parse → compute → print
}Why f64?
Because 7 / 2 is expected to give 3.5, numbers are kept as f64. When printing, {} hides needless zeros: 3.5 → 3.5, 36.0 → 36. Throughout the project you'll move in small steps and try each piece inside main.
Practice First operation
Write the fn topla(a: f64, b: f64) -> f64 function and try it with println!("{}", topla(2.0, 1.5));.
Starter code
fn main() {
// buraya yaz
}Sample solution
fn topla(a: f64, b: f64) -> f64 {
a + b
}
fn main() {
println!("{}", topla(2.0, 1.5));
}Expected output
3.5
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Why does <code>hesapla</code> return <code>Result<f64, String></code>?
- Because it's required
- To be able to report errors such as division by zero and unknown operators Correct answer
- Because it's faster
- Because f64 can't be printed
Explanation: Result carries either the successful value (Ok) or the error (Err); the caller is forced to handle both.
2 Decimal parameter
fn topla(a: ____, b: f64) -> f64 {
a + b
}fn topla(a: f64, b: f64) -> f64 {
a + b
}Explanation: f64 is Rust's default 64-bit floating-point type.
3 Part and role
| Term | Meaning |
|---|---|
main |
Loop and flow |
hesapla |
Performs the operation |
Result |
Success or error |
f64 |
Decimal result |