
```
func add1(y: felt) -> (z: felt) {
    let z = y + 1;
    return (z=z);
}
```


Hello! This is Day 2 of the 17 days of the Cairo challenge. And I have no idea how to solve the [playground](https://www.cairo-lang.org/playground/) exercise “Functions”. Perhaps you can help me?

```python
// The following code is missing the function `add1`.
// 1. Click on "Run" to see the error.
// 2. Write the function `add1`, based on `add1_square`, so
//    that the program terminates successfully.
//
// Note that `add1` doesn't have to call other functions.
//
// You can learn more about functions [here](https://www.cairo-lang.org/docs/how_cairo_works/functions.html).

// Write your code here.

func add1_square(x: felt) -> (x: felt) {
    // Call `add1` and unpack the result into `z`.
    let (z) = add1(y=x);
    return (x=z * z);
}

func main() {
    // Call `add1_square` and save the result into `res`.
    let (res) = add1_square(x=12);

    // Verify the computation.
    assert res = (12 + 1) * (12 + 1);
    return ();
}
```

---
> Answers to this question are a part of the ✨ **17 days of Cairo Lang with Playground & Newton.** ✨ 

*Vote for your favorite answer - the best answer will win a $10 award. A new day – a new reward! During the next 17 days, our goal is to attract more developers to the Cairo language and to systematize the knowledge of Cairo lang. [Read rules](https://www.notion.so/17-days-of-Cairo-Lang-with-Newton-550dfcda6a2d449ca468be293c776578)*

How to write a function in Cairo Lang (StarkNet)?


```
func abs_eq(x: felt, y: felt) -> (bit: felt) {
    if (x == y) {
        return (bit=1);
    }
    if (x == -y) {
        return (bit=1);
    } 
    return (bit=0);
}
```


Hello! This is day 3 of the 17 days of the Cairo Challenge. And I have no idea how to solve the [playground](https://www.cairo-lang.org/playground/) exercise “Conditionals”. Perhaps you can help me?

```python
// The function `abs_eq` should return 1 if its inputs
// are equal or differ only in sign and 0 otherwise.
// Its current implementation is incorrect.
//
// 1. Click on "Run" to see where it fails.
// 2. Fix the body of `abs_eq`, so that the
//    program terminates successfully.

// Returns 1 if |x| = |y| (that is, x = y or x = -y),
// 0 otherwise.
func abs_eq(x: felt, y: felt) -> (bit: felt) {
    if (x == -y) {
        return (bit=1);
    } else {
        return (bit=0);
    }
}

func main() {
    let (bit) = abs_eq(2, -2);
    assert bit = 1;

    let (bit) = abs_eq(2, 3);
    assert bit = 0;

    let (bit) = abs_eq(2, 2);
    assert bit = 1;

    return ();
}
```

---


> Answers to this question are a part of the ✨ **17 days of Cairo Lang with Playground & Newton.** ✨

*Vote for your favorite answer - the best answer will win a $10 award. A new day – a new reward! During the next 17 days, our goal is to attract more developers to the Cairo language and to systematize the knowledge of Cairo lang. [Read rules](https://www.notion.so/17-days-of-Cairo-Lang-with-Newton-550dfcda6a2d449ca468be293c776578)*

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