One case where I have seen this issue is when I am doing some computation and accidentally leave my let statement looking like a let statement for a function return. See the following example.


Say in this case y is a felt = to 10 `let z = y + 1` then this is fine. Also if you are calling a function to add one to y like


 `let (z) = add1(y)` that is fine as you need to unpack the return value. But if you use `let (z) = y + 1`  then you will get that error as you cannot unpack y + 1.


ㅤ
_This answer was originally posted on [Triality](https://triality.org/question/417)_

Just to add to what Mikey is saying here. The reason why you do `let (z) = add1(y)` is that all functions return in the form of a tuple so (arg1, arg2, etc...) so if you want to get the value from a function return you have to use tuple notation (z), however with a regular operation saying `let (z) = y + 1`, y + 1 isn't a tuple so you can't set it equal to a tuple.


ㅤ
_This answer was originally posted on [Triality](https://triality.org/question/417)_

Can someone explain what "Error: ... Cannot unpack x ..." means?


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/417)_

Cairo: Cannot unpack error

Hey! The title sort of summarizes the question. I was wondering if there's any project where I can see an example of how something like `keccak256(abi.encodePacked(var1, var2, var3))`  could be achieved in starknet.

If there were a way to concatenate bytes, I think it wouldn't be too complicated, but such a string would never fit in a felt, and using a struct won't result in the same output.

So yes, my question is if there's an equivalent way to achieve this behavior in cairo.

Equivalent to Solidity's keccak256(abi.encodePacked())?


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)_

output_ptr Assertion Error in Main - Cairo-lang

Can I transpile any solidity version?

The function below is an example. Please ignore the for loop. 


The idea is that I want to keep updating the value largest once I found a number larger than it from the input (a series of numbers bitpacked into Uint256), but I also hope it remains its initialized value if not. Right now if I do the following, the pointers seem to get messed up.


`func getLargest(array) -> (res : felt)`


 `let largest = 5`


 `local currentNum`


 `# pseudocode here, using for loops for simplicity tho cairo doesn't it`


 `for (i=0, i < array.length, i++):`


 `currentNum = array[i]`


 `if (currentNum > largest):`


 `assert largest = currentNum`


 `end`


`﻿`


 `let res = largest`


 `return (res)`


`end`


Test 1


Input(s): 1


Output(s): 5


Test 2


Input(s): 10


Output(s): 10


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/1002)_

Changing a variable with an initialized value recursively with if statements

## What is Kakarot, the zkEVM written in Cairo?


What is Kakarot, the zkEVM written in Cairo?

Hi, I was deploying contracts with `Contract.deploy`, but since the last version this method is gone :/

What should I do to deploy contracts now?

How to deploy a contract through starknet.py?

I'm seeing this error when running the cairo-compile command from Setting up the Environment:


File "marshmallow_dataclass/__init__.py", line 710, in field_for_schema


`RecursionError: maximum recursion depth exceeded in comparison`


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/2)_

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