This is a simple syntax error, your code should look like 


`let (local prev : felt) = fibonacci(n-1)`


If you are trying to combine the let and local in one line.


﻿  



ㅤ
_This answer was originally posted on [Triality](https://triality.org/question/582)_

I am getting the error above when I use the following line:


`let local (prev : felt) = fibonacci(n-1)`


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/582)_

Cairo Error: Unexpected token Token('LPAR', '('). Expected: identifier.

I'm new to Cairo and I want to know what is the difference when I write `let x = 1;` and `tempvar x = 1;`. Is there any difference in Cairo Lang between let and tempvar?

Cairo: let vs tempvar what is the difference?

What is the expected blocktime for starknet mainnet?

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

What is the expected blocktime for starknet mainnet?

does anybody have a working local setup ? I find myself having to run tests on the testnet...

I tried both nile and protostar. the problem is that I can set it up but I don't know how to get access to the accounts that are pre-loaded with ETH. new accounts that I create don't have ETH and I don't have a way to transfer ETH to them..

if anybody has a go-to setup that they can share that'd be much appreciated 🙏

How to setup local Starknet node with Account contracts?

Hey, I’m learning Cairo and I want to know more about Gas Optimization. In Solidity compiler, there is a difference between writing uint128 and uint256. Similarly to C and other languages, for example:

```solidity
contract ThisIsNotAnOptimizedContract{
	uint128 Zero;
	uint256 One;
	uint128 Two;
}

contract ThisIsAGasOptimizedContract{
	uint128 Zero;
	uint128 Two;
	uint256 One;
}

```

`uint128` variables each occupy a separate `uint256`just for themselves, wasting 128 bits for each slot (Like the first contract). The Solidity compiler puts 2 `uint128` in the one 256-bit memory slot when they are declared next to each other. 

I’m curious if there is any similar issue in Cairo. `Uint256` uses two felt objects for low/high bits of the value.

```python
struct Uint256 {
    // The low 128 bits of the value.
    low: felt,
    // The high 128 bits of the value.
    high: felt,
}
```

Is there any similar practice in Cairo to optimize `felt` and Uint256 objects to save some compiler steps?

How do you optimize gas in Cairo with Uint256/felt?

ETH blocks contain logsbloom, giving a partial indication of what events occurred in the block without the need to search every transaction receipt. Many ETH nodes and services also offer “filter” functions.

Is there a way to find events in a block without getting receipt for all transactions on Starknet? 

(I’m using starknet_py but open to any ideas)

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

Is there a way to find events in a block without getting receipt for all transactions on Starknet? 


why does keccak256 replace sha256 in warp transpiler? I want to know: are they technically identical or different?

I am asking because I haven't the support of sha256 on [Github](https://github.com/NethermindEth/warp)

![sha256 is not supported in warp, use keccak256 instead](https://res.cloudinary.com/varga/image/upload/v1671461992/Screen_Shot_2022-12-19_at_18.58.51_dawd8x.png)

why does keccak256 replace sha256 in warp?

Hey guys,
I got this error `The return type of storage variables must be a felts-only type (cannot contain pointers)` when when compiling this:
```
struct MultipleLinear {
    number_of_features: felt,
    coef_s: felt*,
    intercept_: felt,
}
@storage_var
func solution_storage(address: felt) -> (solution: MultipleLinear) {
}
```
Apparently **storage can only return felt**? So what would be the solution if I want it to return an array or a struct that contains felt*?

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Cairo Error: Unexpected token Token('LPAR', '('). Expected: identifier.

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