It takes about 10 hours. After l1 is accepted, you can reconfirm it at starkgate

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

Newton

hi, i used the starkgate bridge from stark to eth one hour ago. Withdrawal has not occurred yet. How many hours does the process take? My tx hash is: <address>cfa0c02d013658804505506

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

How long does starkgate bridge process?

Hello! This is day 7 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 “Recursion”.  Perhaps you can help me?

```
// The following code prints the sum of the numbers from 1 to 10.
// Modify the function `compute_sum` to print all the intermediate sums:
// 1, 1 + 2, 1 + 2 + 3, ..., 1 + 2 + ... + 10.
// Note: you'll have to add the implicit argument output_ptr to the
// declaration of compute_sum (in order to use the serialize_word function):
//   func compute_sum{output_ptr: felt*}(n: felt) -> (sum: felt)

// Use the output builtin.
%builtins output

from starkware.cairo.common.serialize import serialize_word

func compute_sum(n: felt) -> (sum: felt) {
    if (n == 0) {
        // When 0 is reached, return 0.
        return (sum=0);
    }

    // Otherwise, call `compute_sum` recursively to compute 1 + 2 + ... + (n-1).
    let (sum) = compute_sum(n=n - 1);
    // Add the new value `n` to the sum.
    let new_sum = sum + n;
    return (sum=new_sum);
}

func main{output_ptr: felt*}() {
    let (res) = compute_sum(n=10);

    // Output the result.
    serialize_word(res);
    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 recursive function in Cairo Lang?

What libraries are secure to use in the Cairo language? How to know which library is audited? 

What libraries are secure to use in Cairo?

What is the expected blocktime for starknet mainnet?

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

What is the expected blocktime for starknet mainnet?

Since memory cannot be freed, what's the drawback of only using local variables (to avoid revoked refs)? What's the typical use case for tempvars?


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/512)_

Cairo: When do you use tempvar and when do you use local

When it comes to message cancellation (L1 -> L2) you can cancel a message in the case that:
- There is any kind of censorship on StarkNet (sequencer skipped your tx)
- The L2 contract's `` function flow has an assert that fails

Is this correct? Am I missing any other situations where message cancellation would/wouldn't work?

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

Can you explain about cancellation (L1 -> L2) in StarkNet (sequencer)?

In the following function I am presented with the following error, even though my code does not make it to this function. What am I doing wrong?


`func fill_in_row{output_ptr: felt*}(row_idx : felt, row_size : felt, curr_row : felt*) {` 


 `if (row_idx == row_size-2) {`


 `return ();`


 `}`


 `let val : felt = curr_row[row_idx-1] + curr_row[row_idx];`


 `serialize_word(val);`


 `curr_row[row_idx+1] = val;`


 `return fill_in_row(row_idx+1, row_size, curr_row);`


`}`


Error: code:80:5: While expanding the reference 'curr_row' in:


 curr_row[row_idx+1] = val;


 ^******^


code:72:73: Expected a register. Found: [fp + (-4)].


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/1156)_

Cairo Error: Getting Error while setting value of item in array


I am going through the official [Cairo language tutorial](https://www.cairo-lang.org/docs/hello_cairo/dict.html). When I get to the `build_dict` function for the 15-puzzle, I am a bit confused so would like to print out some things to see.



```
struct Location:
    member row : felt
    member col : felt
end

...

func finalize_state(dict : DictAccess*, idx) -> (
        dict : DictAccess*):
    if idx == 0:
        return (dict=dict)
    end

    assert dict.key = idx
    assert dict.prev_value = idx - 1
    assert dict.new_value = idx - 1

    return finalize_state(
        dict=dict + DictAccess.SIZE, idx=idx - 1)
end

##### I added the {} along with context in it for output #####
func main{output_ptr : felt*}():
    alloc_locals

    local loc_tuple : (Location, Location, Location, Location, Location) = (
        Location(row=0, col=2),
        Location(row=1, col=2),
        Location(row=1, col=3),
        Location(row=2, col=3),
        Location(row=3, col=3),
        )

    # Get the value of the frame pointer register (fp) so that
    # we can use the address of loc_tuple.
    let (__fp__, _) = get_fp_and_pc()
    # Since the tuple elements are next to each other we can use the
    # address of loc_tuple as a pointer to the 5 locations.
    verify_location_list(
        loc_list=cast(&loc_tuple, Location*), n_steps=4)

    ##### Here is what I added #####
    local locs : Location* = cast(&loc_tuple, Location*)
    tempvar loc = [locs]
    tempvar row = loc.row
    serialize_word(row)
    ################################

    return ()
end

```

I added the lines for printing the first row in `loc_tuple`. However, the Cairo compiler is giving me the following errors:



```
Traceback (most recent call last):
  File "/Users/yijiachen/cairo_venv/bin/cairo-compile", line 10, in <module>
    sys.exit(main())
  File "/Users/yijiachen/cairo_venv/lib/python3.8/site-packages/starkware/cairo/lang/compiler/cairo_compile.py", line 397, in main
    cairo_compile_common(
  File "/Users/yijiachen/cairo_venv/lib/python3.8/site-packages/starkware/cairo/lang/compiler/cairo_compile.py", line 121, in cairo_compile_common
    assembled_program = assemble_func(
  File "/Users/yijiachen/cairo_venv/lib/python3.8/site-packages/starkware/cairo/lang/compiler/cairo_compile.py", line 367, in 
    cairo_assemble_program
    check_main_args(program)
  File "/Users/yijiachen/cairo_venv/lib/python3.8/site-packages/starkware/cairo/lang/compiler/cairo_compile.py", line 296, in check_main_args
    assert main_args == expected_builtin_ptrs, (
AssertionError: Expected main to contain the following arguments (in this order): []. Found: ['output_ptr'].

```

I have tried with various `serialize_word` statements and none seem to work. This issue never arose before with other `serialize_word` statements, including in earlier parts of the tutorial.



ㅤ
_This question was originally posted on [Stack Overflow](https://stackoverflow.com/questions/70586553/output-ptr-assertion-error-in-main-cairo-lang)_

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