From the docs:


"Builtins are predefined optimized low-level execution units which are added to the Cairo CPU board to perform predefined computations which are expensive to perform in vanilla Cairo (e.g., range-checks, Pedersen hash, ECDSA, …)."


﻿<https://www.cairo-lang.org/docs/how_cairo_works/builtins.html?highlight=range_check_ptr>﻿


﻿[﻿](https://www.cairo-lang.org/docs/how_cairo_works/builtins.html?highlight=range_check_ptr)So if you have access to a builtin and do not need to redefine it, you do not need to explicitly pass it in to a function


ㅤ
_This answer was originally posted on [Triality](https://triality.org/question/413)_

Say I am calling the following function test. Why can I call with either of these function signatures and get the same result?


`func test{syscall_ptr : felt*}():`


or


`func test{syscall_ptr : felt*, range_check_ptr}():`


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/413)_

Cairo: are builtins always needed to be expressed in function signature?

When I try to transpile my contract using warp transpiler I get an error: `JavaScript heap out of memory`

![JavaScript heap out of memory error in Nethermind's warp transpiler](https://res.cloudinary.com/varga/image/upload/v1670423892/Screenshot_2022-11-30_at_7.32.34_PM_pazqli.png)

can anyone help?

update:
I ran this command 
```
export NODE_OPTIONS=--max-old-space-size=4096
```
before transpiling
still show the same error

- Node version is v16.16.0
- warp version  2.4.1
- I tried using node 18 but still same error occured
- I'm using an M1 Mac, 8gb RAM

I'm transpiling llampay contracts : [https://github.com/LlamaPay/llamapay/tree/master/contracts](https://github.com/LlamaPay/llamapay/tree/master/contracts)

The original LlamaPay has some unsupported features in Warp. And I fixed them:
- [LlamaPay.sol](https://pastebin.com/12pSdPBJ) 
- [LlamaPayFactory.sol](https://pastebin.com/DVeuvWKd)


Nethermind's warp error: JavaScript heap out of memory

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

Hey folks, do you know how I could read a felt* from ap?

I want to do something like this:

```rs
    let (hello : felt*) = alloc();
    tempvar world : felt* = hello;
    let world_like : felt* = [ap-1];
```

when I do tempvar world = hello, I ensure I add hello (the pointer) to [ap] and then I increase ap so world_like = [ap-1] should be the same thing than world

But I get this error:

```
Cannot assign an expression of type 'felt' to a reference of type 'felt*'.
    let world_like : felt* = [ap-1];
```

When doing a similar code:

```rust
        let (func_pc: felt*) = get_label_location(storage_var);
        _prepare_call(pedersen_ptr, range_check_ptr, len_inputs, inputs + len_inputs);
        call abs ap[11 - 6 * 2];
```

I get ```
Cannot apply subscript-operator to non-pointer, non-tuple type 'felt'.
        call abs ap[11 - 6 * 2];  // removing alloc_locals by calling ap[11-6*2] ?
```

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

how I could read a felt* from ap in Cairo lang?

Hello guys, does one know how to modify keccak.cairo and/or packed_keccak.cairo to compute a 512bits keccak hash instead of 256 bits?

I'm following a paper that needs 256 bits collision resistance so i need 512 bit keccak. 

There should only a few parameters to change but its quite hard to find them in the Cairo code 

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

---

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How to modify keccak.cairo and/or packed_keccak.cairo to compute a 512bits keccak hash instead of 256 bits?


**I want to put a disconnect button in my dapp, does anyone know how to do this on the frontend?**

anyone know how to disconnect the connected wallet on the frontend with starknetjs or another way?

Hello, I deployed my contract using Argent X.
I click on "Developer settings" and then "Smart contract developement". I declare and deploy the contract.
Also used [this guide](https://www.newton.so/view/63a1890e581919f84b2a4c51) and it helped me.

But the contract is not automatically verified on starkscan or voyager. What should I do to get verified?

How can I verify a contract on starkscan or voyager after deploying the contract

Hello, anyone able to advise what the etherscan equivalent for starknet is ?

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

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