Only `and` is currently supported in if-statements. If you want to get `or` then in this case you can do
```
if ((x - y) * (x + y) == 0) {...}
```
Then, if x == y then the first factor will be zero (and therefore the entire expression will be zero), and if x == -y then the second factor will be zero, so it basically functions like an `or`


_This answer was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

Newton

I'm very curious: does Cairo have any logic operators? I found bitwise_or bitwise_and etc. but it is not wokring if I want to do something like

if (x == y) OR (x == -y) { ... }

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

Does Cairo Lang have any logic operators?

# Will Kakarot be an L3 on top of the Starknet validity rollup?

Will Kakarot be an L3 on top of the Starknet validity rollup?

How do I use keccak functions in Cairo? I am getting the error `Unknown identifier 'bitwise_ptr'` 


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/662)_

Cairo error: Unknown identifier 'bitwise_ptr' when using keccak

Hello! This is day 8 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 “Field Elements”.  Perhaps you can help me?

```
// Unlike most systems where the primitive type is a 32 or 64-bit integer,
// the primitive type in Cairo is "felt", which stands for "field element".
// When we say "a field element" we mean an integer in the range -P / 2 < x < P / 2,
// where P is a very large (prime) number.
// Currently we use a 252-bit number (76 decimal digits).
// When we add, subtract or multiply and the result is outside the range above,
// there is an overflow.
//
// The most important difference between integers and field elements is division:
// Division of field elements (and therefore division in Cairo) is not the
// integer division you may be used to.
// In the next challenge, you'll see how to use unsigned_div_rem()
// for truncated (i.e., rounding down) integer division.
//
// Make the code below output the results of the following expressions:
// 1. 1 + 100, 1 - 100, 9 * 9.
// 2. pow(10, 74), pow(10, 75), pow(10, 76)
// 3. 12 / 3, (-12) / 3
// 4. 13 / 3 (This is an example of division in the field)

%builtins output

from starkware.cairo.common.serialize import serialize_word

// Computes base^exp.
func pow(base: felt, exp: felt) -> (res: felt) {
    if (exp == 0) {
        return (res=1);
    }

    let (res) = pow(base=base, exp=exp - 1);
    return (res=res * base);
}

func main{output_ptr: felt*}() {
    serialize_word(1 + 100);
    // Add your code here.

    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 make math operation with Field Elements (felts) in Cairo lang?

Can I transpile any solidity version?

Hello! This is day 17 of the 17 days of the Cairo Challenge. In this challenge I want to ask you [install](https://www.cairo-lang.org/docs/quickstart.html) Cairo and try to launch your first program. What have you implemented as your first Cairo language program?

**Step 1**
```solidity
// 1. Make sure that you installed dev packages on your device
sudo apt install -y libgmp3-dev // Linux
brew install gmp // Mac OS
```
**Step 2**
```solidity
// 2. Install Cairo using Python virtual environment
python3.9 -m venv ~/cairo_venv
source ~/cairo_venv/bin/activate
pip3 install ecdsa fastecdsa sympy;
pip3 install cairo-lang;
```
**Step 3**
```bash
// 3. Make sure you have python 3.9. Because Cairo was tested with python3.9. To make it work with python3.6, you will have to install contextvars:
pip3 install contextvars
```
**Step 4**
```python
// 4. Write your program
// Create a file, named hello.cairo, with the following lines:
 
func main() {
		// edit me: you can add here any output, best program wins the challenge
    ret;
}

```solidity
//5. Compile your program
cairo-compile hello.cairo --output hello_compiled.json
```
**Last step**
```solidity

//6. Run:
cairo-run \
  --program=hello_compiled.json --print_output \
  --print_info --relocate_prints

//7. Debug:
//You can open the Cairo tracer by providing the --tracer flag to cairo-run. Then open it at http://localhost:8100/.
```
If you have questions, create them on Newton and we will help!

---
> 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 install Cairo v0.10.0 on my device?

Can someone explain what "Error: ... Cannot unpack x ..." means?


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/417)_

Cairo: Cannot unpack error

Hello, I am trying to implement the connect wallet : ``` import { useConnectors } from '-react/core' function YourComponent() { const { connect, connectors } = useConnectors() return ( <div> {connectors.map((connector) => connector.available() ? ( <button key={connector.id()} onClick={() => connect(connector)}> Connect {connector.name()} </button> ) : null )} </div> ) } ``` I feel like connectors will only give the wallet if I have it on my chrome extensions , so whats the point of connector.available() ? I am using : ``` const connectors = getInstalledInjectedConnectors() ```

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

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