Here are 2 approaches:


1) Use the following code snippet to create an array size 3 using alloc() - make sure you include 


`from starkware.cairo.common.alloc import alloc`


 `let felt_array : felt* = alloc()`


 `assert [felt_array] = 1`


 `assert [felt_array+1] = 2`


 `assert [felt_array+2] = 3`


﻿  



2) Use the new operator to create a fixed sized array in a single line


`tempvar arr : felt* = new (1, 2, 3)`


ㅤ
_This answer was originally posted on [Triality](https://triality.org/question/400)_

I want to do some unit testing and need to pass in a felt* of value [1,2,3] into my function. How do I do this?


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/400)_

Cairo: How do I initialize an array in cairo

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Hello! I was wondering whether it was possible to check if a certain address has code in Cairo.
In Solidity, we do something like:

```
assembly {
  codeSize := extcodesize(contractAddress)
}
or just:
uint256 codeSize = contractAddress.code;
```
I was wondering if there was a way to check something like this in cairo? I checked the syscalls file but didn't find anything promising there.

Thank you in advance!

How to check if a contract has been deployed at a certain address in cairo?

Hello there,

Do you know why `pedersen_hash` needs to split felts in low 248 and high 4 bits? 

---

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Why does Starkware pedersen Hash Function split numbers in high and low bits

# Is Kakarot part of the Starknet ecosystem?

Is Kakarot part of the Starknet ecosystem?

Hello! This is day 10 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 “Bitwise operations”.  Perhaps you can help me?

```
// The bitwise builtin allows you to perform bitwise operations
// (and, or, xor) on integers up to 251 bits.
//
// The following code implements the function xor_last_hex_digits,
// which takes the two last hexadecimal digits and "xor"s them.
// For example, in 0x1234 the last two digits are 3 and 4,
// and their xor is 3^4=7.
//
// Fix the missing code and make sure it works.

%builtins bitwise

from starkware.cairo.common.bitwise import bitwise_and, bitwise_xor
from starkware.cairo.common.cairo_builtins import BitwiseBuiltin

// Returns the xor of the last two hexadecimal digits.
func xor_last_hex_digits{bitwise_ptr: BitwiseBuiltin*}(x: felt) -> (res: felt) {
    // Fix and uncomment the line below.
    // let (digit0) = ...

    let (shifted_digit1) = bitwise_and(x, 0xF0);
    tempvar digit1 = shifted_digit1 / 0x10;

    return bitwise_xor(digit0, digit1);
}

func main{bitwise_ptr: BitwiseBuiltin*}() {
    let (res) = xor_last_hex_digits(0x1234);
    assert res = 7;

    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 Bitwise operations in Cairo Lang using %builtins bitwise, bitwise_xor?

Why am I getting an `account __execute__` error message `ape_starknet.exceptions.StarknetProviderError: Can only send invoke transaction to an account execute method`?


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