Project design
- Go course
- Beginner
- Lesson 25/90
- 6 min
Design the calculator skeleton and menu structure.
Project: a calculator
In this project you will write a command-line calculator that does four operations. First design the structure: each operation is a separate function, and hesapla picks the right one by the operator symbol.
func topla(a, b float64) float64
func cikar(a, b float64) float64
func carp(a, b float64) float64
func bol(a, b float64) (float64, error)
func hesapla(a float64, islem string, b float64) (float64, error)Splitting into small functions makes each piece easy to try on its own.
Why float64?
In a calculator 7 / 2 is expected to give 3.5. That's why numbers are kept as float64. When printing, the %g format hides needless zeros: 3.5 → 3.5, 4.0 → 4.
Practice Skeleton
Write the topla(a, b float64) float64 function and try it with fmt.Printf("%g\n", topla(2, 1.5)).
Starter code
package main
import "fmt"
func main() {
// buraya yaz
}Sample solution
package main
import "fmt"
func topla(a, b float64) float64 { return a + b }
func main() {
fmt.Printf("%g\n", topla(2, 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 only the <code>bol</code> function return an <code>error</code>?
- The others should too
- It is the only operation that can fail, e.g. division by zero Correct answer
- Division is slower
- Go requires an error for division
Explanation: Addition, subtraction and multiplication always give a result; division is undefined at zero and must report it to the caller.
2 Two return values
func bol(a, b float64) (float64, ____) {func bol(a, b float64) (float64, error) {Explanation: Functions that can fail return an error as their last value.
3 Function and role
| Term | Meaning |
|---|---|
topla |
a + b |
bol |
a / b and an error |
hesapla |
Chooses by operation |
%g |
Hides needless zeros |