public/subjects/atoiprog.en.md

## atoiprog

##**WARNING! VERY IMPORTANT!**

For this exercise a function will be tested **with the exam own main**. However the student **still needs** to submit a structured program:

This means that:

- The package needs to be named `package main`.
- The submitted code needs one declared function main(```func main()```) even if empty.
- The function main declared needs to **also pass** the `Restrictions Checker`(illegal functions tester). It is advised for the student to just empty the function main after its own testings are done.
- Every other rules are obviously the same than for a `program`.

### Instructions

-   Write a [function](TODO-LINK) that simulates the behaviour of the `Atoi` function in Go. `Atoi` transforms a number represented as a `string` in a number represented as an `int`.

-   `Atoi` returns `0` if the `string` is not considered as a valid number. For this exercise **non-valid `string` chains will be tested**. Some will contain non-digits characters.

-   For this exercise the handling of the signs + or - **does have** to be taken into account.

-   This function will **only** have to return the `int`. For this exercise the `error` result of atoi is not required.

### Expected function

```go
func Atoi(s string) int {

}
```

### Usage

Here is a possible [program](TODO-LINK) to test your function :

```go
package main

import (
	"fmt"
)

func main() {
	s := "12345"
	s2 := "0000000012345"
	s3 := "012 345"
	s4 := "Hello World!"
	s5 := "+1234"
	s6 := "-1234"
	s7 := "++1234"
	s8 := "--1234"

	n := Atoi(s)
	n2 := Atoi(s2)
	n3 := Atoi(s3)
	n4 := Atoi(s4)
	n5 := Atoi(s5)
	n6 := Atoi(s6)
	n7 := Atoi(s7)
	n8 := Atoi(s8)

	fmt.Println(n)
	fmt.Println(n2)
	fmt.Println(n3)
	fmt.Println(n4)
	fmt.Println(n5)
	fmt.Println(n6)
	fmt.Println(n7)
	fmt.Println(n8)
}
```

And its output :

```console
student@ubuntu:~/piscine-go/test$ go build
student@ubuntu:~/piscine-go/test$ ./test
12345
12345
0
0
1234
-1234
0
0
student@ubuntu:~/piscine-go/test$
```