Pathfinder provides an RPC API with which you can query StarkNet data and state, and simulate and submit transactions. Pathfinder also provides a basic monitoring API which can provide insight into the node’s status.


RPC API: https://github.com/eqlabs/pathfinder#json-rpc-api

Basic monitoring API: https://github.com/eqlabs/pathfinder#monitoring-api

How do I interact with my Pathfinder node?

Hey guys! Does anybody have an idea what is `get_caller_address` returning on an L1 handler call?

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

Does anybody have an idea what is `get_caller_address` returning on an L1 handler call?

Starknet is using which oracle service provider?

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

Which oracle service provider is StarkNet using?

How do I see my Pathfinder logs?

Hello! This is day 9 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 “Field Elements 2”.  Perhaps you can help me?

```
// As you saw in the previous challenge, the operator '/' does not denote
// truncated (i.e., rounding down) integer division as in other programming
// languages. Instead, one can use library functions such as
// unsigned_div_rem().
//
// Note that unsigned_div_rem() does not work for negative numbers.

%builtins output range_check

// Import unsigned_div_rem() from the math module.
from starkware.cairo.common.math import unsigned_div_rem
from starkware.cairo.common.serialize import serialize_word

func main{output_ptr: felt*, range_check_ptr}() {
    let (q, r) = unsigned_div_rem(value=12, div=3);
    // Output the quotient (12 // 3).
    serialize_word(q);
    // Output the remainder (12 % 3).
    serialize_word(r);

    // Add code that outputs the quotient and remainder of 13 / 3 in addition to 12 / 3 here.

    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 divide felt in Cairo Lang using unsigned_div_rem?

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 is Kakarot, the zkEVM written in Cairo?


What is Kakarot, the zkEVM written in Cairo?

Hey guys,
I'm wondering:
- What **hashing functions** are available now with Cairo?
- What are the **advantages/disadvantages** of each, like computation, security?

So far I know some:
- [keccak](https://github.com/starkware-libs/cairo-lang/tree/master/src/starkware/cairo/common/cairo_keccak)
- Pedersen hash, which can be used to hash chain, [here](https://www.newton.so/view/63427472405280f6d1cf502d)
- [sha256 extension](https://github.com/cartridge-gg/cairo-sha256) of the starkware implementation which can Computes SHA256 of 'input'. Inputs of arbitrary length are supported.

Happy hashing :)



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