You can make multicalls and batch many transactions that execute one after the other


See the following code from @[﻿](https://t.me/bowlofchilli)bowlsofchili in Telegram:


`export const constructTransaction = (contract, method, args = {}) => {`


`﻿`


 `const calldata = stark.compileCalldata(args);`


`﻿`


 `const transaction = {`


`﻿`


 `contractAddress: contract.address,`


`﻿`


 `entrypoint: method,`


`﻿`


 `calldata`


`﻿`


 `};`


`﻿`


 `return transaction`


`﻿`


`};`


`﻿`


`﻿`


`﻿`


`﻿`


`export const sendTransactions = async (transactions) => {`


`﻿`


 `try {`


`﻿`


 `return await getStarknet().account.execute(transactions);`


`﻿`


 `} catch (ex) {`


`﻿`


 `return Promise.reject(ex);`


`﻿`


 `}`


`﻿`


`};`


see above, first method will help contruct individual txs and the second execute all of them at once


ㅤ
_This answer was originally posted on [Triality](https://triality.org/question/1218)_

Looking to call the approve and transfer functions for an erc-20 in the same transaction. Thoughts on how to do this?


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/1218)_

Cairo: How can i approve erc20 and transfer in the same transaction?

Guys, what`s ArgentX?

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

What is ArgentX?

Hello! This is day 12 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 “Structs.  Perhaps you can help me?

```
// In this challenge you're going to implement a stack using a linked list.
//
// Add the missing code so that main() runs successfully.

from starkware.cairo.common.registers import get_fp_and_pc

struct Node {
    // A pointer to the next node in the stack.
    next: Node*,

    // The value of the node.
    value: felt,

    // The number of elements in the stack.
    size: felt,
}

// Returns an empty stack.
func empty_stack() -> (stack: Node*) {
    alloc_locals;
    local new_node: Node;
    assert new_node.next = cast(0, Node*);
    assert new_node.value = 0;
    assert new_node.size = 0;

    // The usage of get_fp_and_pc() here is necessary in order
    // to access the address of a local variable (&new_node).
    // You can read more about get_fp_and_pc() [here](https://cairo-lang.org/docs/how_cairo_works/functions.html#retrieving-registers).
    let (local __fp__, _) = get_fp_and_pc();
    return (stack=&new_node);
}

// Adds a node to the top of the stack.
// Returns the updated stack (since Cairo is immutable, you can still use the
// old copy of the stack).
func push(stack: Node*, value: felt) -> (stack: Node*) {
    alloc_locals;
    local new_node: Node;
    // Fix and uncomment below.
    // assert new_node.next = ...
    // assert new_node.value = ...
    // assert new_node.size = ...

    let (__fp__, _) = get_fp_and_pc();
    return (stack=&new_node);
}

// Removes the top element of the stack.
// Returns the updated stack and the element that was removed.
func pop(stack: Node*) -> (stack: Node*, value: felt) {
    return (stack=stack.next, value=stack.value);
}

// Returns the value of the n-th element from the top of the stack.
func stack_at(stack: Node*, n: felt) -> (value: felt) {
    if (n == 0) {
        // Add your code here.
    }

    // Add your code here.
}

func main() -> () {
    alloc_locals;
    // Start with an empty stack.
    let (stack) = empty_stack();
    // Push 1, 10, 100.
    let (stack) = push(stack, 1);
    let (stack) = push(stack, 10);
    let (local stack) = push(stack, 100);

    // Check the size of the stack.
    assert stack.size = 3;

    // Query the stack at indices 0, 1 and 2.
    let (value) = stack_at(stack, 0);
    assert value = 100;
    let (value) = stack_at(stack, 1);
    assert value = 10;
    let (value) = stack_at(stack, 2);
    assert value = 1;

    // Pop the top 2 values (100 and 10) and push 1000.
    let (stack, value) = pop(stack);
    assert value = 100;
    let (stack, value) = pop(stack);
    assert value = 10;
    let (local stack) = push(stack, 1000);

    // Query the stack at indices 0 and 1.
    let (value) = stack_at(stack, 0);
    assert value = 1000;
    let (value) = stack_at(stack, 1);
    assert value = 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 create Structs in Cairo Lang for StarkNet?

Everyone knows that secure code is essential. Can someone explain what is reentrancy?
I am curious about the reentrancy attack in StarkNet – is it a problem in Cairo Language and how to protect my smart contract from this attack?

How to protect my contract from reentrancy in Cairo Language / StarkNet?

Would really like to understand how a full node for Starknet like pathfinder works

How does a full node like pathfinder work

In the medium article about 1.0.0 this is shown as the syntax for the for loop

```let sum = 0
for x in iter {
  sum = sum + x;
}```

That doesn't compile for me and loops are not mentioned on github release note.

Will recursion still be necessary if they work as they do in other languages? 

Will it be possible to invoke functions from within the loops?

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

Will it be possible to invoke functions from within the loops in Cairo 1.0?

How can I connect to deployed StarkNet contract using starknetjs?

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)_

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