gnart33 / 100dayscairo

100 days Cairo

day 1

Hi gang, I'm trying to solve day 13 of the 17 days of the Cairo Challenge: Pedersen Hash This is my solution so far

// Computes the Pedersen hash chain on an array of size `length` starting from `data_ptr`.
func hash_chain{hash_ptr: HashBuiltin*}(data_ptr: felt*, length: felt) -> (result: felt) {
    if (length == 2) {
        let (result) = hash2(x=[data_ptr], y=[data_ptr + 1]);
        return (result=result);
    } else {
        // Fix here:
        let x_n: felt = data_ptr[length];
        result = hash2(hash_chain(data_ptr, length - 1), x_n);
        return (result=result);
    }
}

And I got revoked and I have no idea what's going on. Can anyone please explain? TIA

Error: code:29:9: Reference 'result' was revoked.
        result = hash2(tmp, x_n);
        ^****^

Feel like start in the middle of the ocean.

day 2

Cairo playground

• 05_variables
  • let, tempvar and local: let creates lot of temporary variables

day 3

Cairo playground

06_revoke_references

To be honest have little idea what happend

• this will not give error

func main{output_ptr: felt*}() {
    let (x) = foo(10);
    let (y) = foo(5);
    return ();
}

• But adding serialize_word(x + y); will give error

func main{output_ptr: felt*}() {
    let (x) = foo(10);
    let (y) = foo(5);
    serialize_word(x + y);
    return ();
}

• 2 ways to fix error:

  • alloc_locals;
  • ap += SIZEOF_LOCALS; let (local x) = foo(10); let (local y) = foo(5);

• Local variables are not revoked when functions are called

• Read more about local variables here

07_dynamic_allocation

• segments mechanism
• Thanks to this mechanism, alloc allocates an array of an arbitrary size, which does not need to be specified in the call.

func sqr_array(array: felt*, length: felt) -> (new_array: felt*) {
    alloc_locals;

    // allocate new memory slot for new_array
    let (local new_array) = alloc();

    // calculate the new_array by the helper function _inner_sqr_array
    // this function does return anything
    _inner_sqr_array(array=array, new_array=new_array, length=length);
    return (new_array=new_array);
}

day 4

Cairo playground

08_recursion

09_field_elements

10_field_elements_02

Just totally random thought, play with output_ptr by serialize_word

11_bitwise_operations

day 5

Cairo playground

12_address_of_locals

let (__fp__, _) = get_fp_and_pc(); // need this to work
local x: felt;

local y: felt* = &x; // y is a pointer at position of felt x
assert [y] = 1234;

13_struct

• Implementation of a stack using a linked list.

  • Remind of CS50 C lession, linked list element contains (next: pointer*, value, size)

• To turn memory address into a pointer we have to use the & operator.

• By default the compiler wouldn’t know what type of pointer this is so to inform it of the type we have to use the function cast and provide the type as the second argument

• new_node.next = cast(0, Node*);: pointer to the 1st Node struct

14_pedersen_hash

• implements a Pedersen hash chain.

• tried this simple recursion but got revoked

Error: code:28:9: Reference 'result' was revoked.
        result = hash2(hash_chain(data_ptr, length - 1), x_n);
        ^****^

func hash_chain{hash_ptr: HashBuiltin*}(data_ptr: felt*, length: felt) -> (result: felt) {
    if (length == 2) {
        let (result) = hash2(x=[data_ptr], y=[data_ptr + 1]);
        return (result=result);
    } else {
        // Fix here:
        let x_n: felt = data_ptr[length];
        result = hash2(hash_chain(data_ptr, length - 1), x_n);
        return (result=result);
    }
}

day 6

15_hints

• The idea is that the verifier only needs to be convinced that res * res = n, it doesn't really care how res was computed.
• In such cases, we don't have to compute res in pure Cairo - we can write a piece of Python code inside the Cairo program, which is called a "hint".
• From the verifier's point of view, the hint is completely transparent.

16_SHARP

wtf

17_StarkNet_contract

18_Cairo_games_example

prover, verifier, sharp, where it goes

day 7

The utils.py is useful for type conversion

MAX_LEN_FELT = 31


def str_to_felt(text):
    if len(text) > MAX_LEN_FELT:
        raise Exception("Text length too long to convert to felt.")

    return int.from_bytes(text.encode(), "big")


def felt_to_str(felt):
    length = (felt.bit_length() + 7) // 8
    return felt.to_bytes(length, byteorder="big").decode("utf-8")


def str_to_felt_array(text):
    return [str_to_felt(text[i:i+MAX_LEN_FELT]) for i in range(0, len(text), MAX_LEN_FELT)]


def uint256_to_int(uint256):
    return uint256[0] + uint256[1]*2**128


def uint256(val):
    return (val & 2**128-1, (val & (2**256-2**128)) >> 128)


def hex_to_felt(val):
    return int(val, 16)

>>> uint256(5)
(5, 0)

>>> uint256_to_int((5,1))
340282366920938463463374607431768211461

>>> uint256(340282366920938463463374607431768211461)
(5, 1)

>>> 2**128
340282366920938463463374607431768211456

>>> uint256(340282366920938463463374607431768211456)
(0, 1) 

day 8

• Dictionary
  • A dictionary is created using the default_dict_new() module from the Common Library
  • https://perama-v.github.io/cairo/examples/default_dict/
• Something with a graph that might be well related, PAKHET Cairo game

day 9

• default_dict.cairo

. . .

day 14

• skip, not really skip but tried different approach to solve a particular problem, ml-starknet
• but sometime, you dont know what you dont know so resuming

StarkNet messaging bridge

ex0

• call ex_0_a, with L1 address, amount = 1
• rank will be assigned

day 15

• Unexpected implicit argument 'hash_ptr' in an external function.

  • dont put hash_ptr as argument
  • use pedersen_ptr: HashBuiltin*,
  • in the function that need hash_ptr define it explicitly e.g hash2{hash_ptr=pedersen_ptr}

• facing issue on starknet declare

❯ starknet declare --contract artifacts/contract.json
Error: KeyError: 'deployed'

day 16

• nile declare
• nile setup got weird

❯ echo $PKEY2
key exists

❯ nile setup PKEY2
❌ Cannot find PKEY2 in env.
Check spelling and that it exists.
Try moving the .env to the root of your project.

• work around

PKEY1=_key_ nile setup PKEY1

• PKEY=_key_ nile declare contract also work
• nile deploy contract 3 --network goerli
  • worked
  • no need --class_hash
  • takes care of declaration