You must remember to declare your contract to publish them to the chain before deploying your contract. You only need to declare your contract once but you can deploy the contract multiple times afterwards. 

Why am I having trouble deploying my Cairo contract?

How do I connect my wallet to my Pathfinder node?

How can I use the meta-class of contract (starknetjs) for interaction?

How can I use meta-class of contract (starknetjs) for interaction?

How can I send a Uint256 amount of ERC20 tokens from L1 to starknet?
I have "amount" as a uint256 on L1 but how should I build my payload for "`sendMessageToL2`" to match the Uint256 format of Cairo?

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How can I send a Uint256 amount of ERC20 tokens from L1 to starknet? And how should I build my payload for "sendMessageToL2" to match the Uint256 format of Cairo?

I am trying to deploy my contract using this tutorial
[https://medium.com/starknet-edu/deploying-to-starknet-with-the-universal-deployer-contract-c6de07092bfb](https://medium.com/starknet-edu/deploying-to-starknet-with-the-universal-deployer-contract-c6de07092bfb)
But as I follow the steps, I got an error at the contract declaration step: `Unitialized Contract`

Trying to deploy contract with Argent guide but got error Unitialized Contract

Hello! This is day 13 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 “Pedersen Hash”.  Perhaps you can help me?

```
// The following code implements a Pedersen hash chain.
// Given the [Pedersen hash](https://docs.starkware.co/starkex-docs/crypto/pedersen-hash-function) function `H`, which
// takes two field elements and returns one representing their hash,
// a hash chain on inputs x_0, x_1, ..., x_n is the result of
// H(H(...H(H(x_0, x_1), x_2), ...,x_{n-1}), x_n)
// For example, the hash chain of (1, 2, 3, 4) is H(H(H(1, 2), 3), 4).
//
// Fix the function `hash_chain` to correctly implement the
// hash chain. Run your code to test it.
//
// Note: Don't use starkware.cairo.common.hash_chain (it computes the chain differently).

// Use the Pedersen builtin.
%builtins pedersen

from starkware.cairo.common.alloc import alloc
from starkware.cairo.common.cairo_builtins import HashBuiltin
from starkware.cairo.common.hash import hash2

// Computes the Pedersen hash chain on an array of size `length` starting from `data_ptr`.
func hash_chain{hash_ptr: HashBuiltin*}(data_ptr: felt*, length: felt) -> (result: felt) {
    if (length == 2) {
        let (result) = hash2(x=[data_ptr], y=[data_ptr + 1]);
        return (result=result);
    } else {
        // Fix here:
        return (result=123456);
    }
}

func main{pedersen_ptr: HashBuiltin*}() {
    alloc_locals;
    // Allocate a new array.
    let (local data_ptr: felt*) = alloc();
    // Fill the new array with field elements.
    assert [data_ptr] = 314;
    assert [data_ptr + 1] = 159;
    // Run the hash chain.
    let (result) = hash_chain{hash_ptr=pedersen_ptr}(data_ptr=data_ptr, length=2);
    // Check the result.
    assert result = 307958720726328212653290369969069617958360335228383070119367204176047090109;

    // Fill two more cells in the array.
    assert [data_ptr + 2] = 265;
    assert [data_ptr + 3] = 358;
    // Compute the hash chain on all four cells.
    let (result) = hash_chain{hash_ptr=pedersen_ptr}(data_ptr=data_ptr, length=4);
    assert result = 1828757374677754028678056220799392919487521050857166686061558043629802016816;
    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 use Pedersen Hash in StarkNet / Cairo Language?

Can tempvar be of a different type, say U256?

let's say

`tempvar foo: U256 = bar;` and bar being a U256?

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

Can tempvar be of a different type, say U256?


My ABIs will be same right? In UI I am assuming I wont have to make any changes

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Why am I having trouble deploying my Cairo contract?

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