would this help:
[https://github.com/Shard-Labs/starknet-hardhat-plugin#recompilation](https://github.com/Shard-Labs/starknet-hardhat-plugin#recompilation)

Hey, while using hardhat test, do we have to manually compile all the contracts again? Bcz if I don’t, it’s still using old compilation and not new contract changes.

Just trying to understand if there is a better way. In solidity, it used to auto compile and that too only changed contracts.

Newton

hardhat test

Hello, is there a javascript version of StarkEx playground?

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

Is there a javascript version of StarkEx playground?

This isn't a starknet question, but raw cairo. is it possible to use a pointer reference like let, and set it to a pointer with a hint, without doing a memory allocation?

looks like the answer is yes, but you do need to assign a reference when you declare a pointer reference with let, but that doesn't alter the memory

e.g.

```python
let s : felt* = cast(ap, felt*)
{
	ids.s = some_other_reference
}
```

the `cast(ap, felt*)` does nothing, just satisfies the compiler by having something on the rhs of a let

a pointer with a hint, without doing a memory allocation

hi all. If I want to use starkex do I have to deploy my custom starkex contracts ?
however in my understanding startex is a protocol where I have to intergrate my dapp specific tx, isn't it ?
in the playground I saw there're some preimplemented tx like ERC20 interface 
is starknet a starkex with an integrated VirtualMachine ?

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

If I want to use starkex do I have to deploy my custom starkex contracts?

In solidity I can add an error message as the 2nd argument to require, like: `require(<some_condition>, "My error message");`


Is there an equivalent way to do this in a starknet contract? Like for `assert some_var = 0`


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/795)_

Cairo: How do I write a custom error message when an assert fails?

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)?

What libraries are secure to use in the Cairo language? How to know which library is audited? 

What libraries are secure to use in Cairo?

How can I write contact memory with Account.execute in starknetjs?

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