# Provider object: 🔌 connect to the network :

The first thing to do: is defined with which network you want to interact. With the Provider object, you define the network to use :

`import {Provider} from 'starknet';`

## Connect your DAPP to a Starknet node :

For a local [Pathfinder](https://github.com/eqlabs/pathfinder) node :

`const provider = new Provider({ rpc: { nodeUrl: '127.0.0.1:9545' } })`

Newton

How do I connect my DAPP to a Starknet node using starknetjs?

Bumped into rc_bound today and was wondering: where/how is it defined and why is it much smaller than the field prime?

Cairo: Where/how is it defined and why is it much smaller than the field prime?

What are implicit arguments in Cairo? When would you use them instead of normally passing in arguments to a function?


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/580)_

Implicit Arguments in Cairo

Hey, I'm using StartkNet.py to make a transaction and it gets rejected. 
How to solve it?

What does this error means? (AssertionError: assert_not_zero failed: 0 = 0.)

Hi all,

Am planning on starting a mainnet node and running it in a docker container as per these instructions:
https://github.com/eqlabs/pathfinder/#running-with-docker

My question:
I am already running a full Ethereum node on my server. I this case, can I set the  PATHFINDER_ETHEREUM_API_URL parameter to my node's endpoint, i.e. 127.0.0.1:[eth node rpc port]?

Thx.

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

I am already running a full Ethereum node on my server. Can I set the  PATHFINDER_ETHEREUM_API_URL parameter to my node's endpoint for pathfinder?

Hello! This is day 6 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 “Dynamic allocation”.  Perhaps you can help me?

```
// Dynamic allocation in Cairo is done using the `alloc` function,
// which itself is implemented in Cairo using the
// [segments](https://www.cairo-lang.org/docs/how_cairo_works/segments.html) mechanism.
// Thanks to this mechanism, `alloc` allocates an array of an arbitrary size,
// which does not need to be specified in the call.
//
// The function `sqr_array` should compute and return an array
// of the square values of a given array.
// Write the body of `sqr_array` using the given helper function
// `_inner_sqr_array` and check that the program output
// is 1, 4, 9, 16.
// `sqr_array` should allocate the new array it returns.

// Use the output builtin.
%builtins output

from starkware.cairo.common.alloc import alloc
from starkware.cairo.common.serialize import serialize_word

// Fills `new_array` with the squares of the first `length` elements in `array`.
func _inner_sqr_array(array: felt*, new_array: felt*, length: felt) {
    if (length == 0) {
        return ();
    }

    assert [new_array] = [array] * [array];

    _inner_sqr_array(array=array + 1, new_array=new_array + 1, length=length - 1);
    return ();
}

func sqr_array(array: felt*, length: felt) -> (new_array: felt*) {
    // Write your code here.
}

func main{output_ptr: felt*}() {
    alloc_locals;
    // Allocate a new array.
    let (local array) = alloc();
    // Fill the new array with field elements.
    assert [array] = 1;
    assert [array + 1] = 2;
    assert [array + 2] = 3;
    assert [array + 3] = 4;

    let (new_array) = sqr_array(array=array, length=4);
    serialize_word([new_array]);
    serialize_word([new_array + 1]);
    serialize_word([new_array + 2]);
    serialize_word([new_array + 3]);

    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 can I use dynamic allocation in Cairo? 


I built a module with Cairo language and I would like to unit test it. The contract is pretty simple : it manages a list of authorized addresses and provide some "modifier" functions to help.


I have taken the sample unit testing code from the documentation but nothing is referring about sending an account address to a function with python.


How should I proceed ?


Thanks in advance



ㅤ
_This question was originally posted on [Stack Overflow](https://stackoverflow.com/questions/73034919/testing-starknet-cairo-contract-function-with-address)_

Testing Starknet Cairo contract function with address

Where can I learn more about starknet?

What is starknet all about people

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

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How do I connect my DAPP to a Starknet node using starknetjs?

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Provider object: 🔌 connect to the network :

Connect your DAPP to a Starknet node :

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