Project skeleton

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.

Exercise First operation

Write the fn topla(a: f64, b: f64) -> f64 function and try it with println!("{}", topla(2.0, 1.5));.

Show example solution

fn topla(a: f64, b: f64) -> f64 {
    a + b
}

fn main() {
    println!("{}", topla(2.0, 1.5));
}

Test yourself

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
- Because it's faster
- Because f64 can't be printed
Show answer

To be able to report errors such as division by zero and unknown operators — Result carries either the successful value (Ok) or the error (Err); the caller is forced to handle both.

Decimal parameter

fn topla(a: ____, b: f64) -> f64 {
    a + b
}

Show answer

fn topla(a: f64, b: f64) -> f64 {
    a + b
}

Part and role

main

Loop and flow
hesapla

Performs the operation
Result

Success or error
f64

Decimal result

Next lesson: Reading input

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