Cairo vector

.cairo

# @title The beginnings of Vector in Cairo
# @author 0xNonCents
# @notice Please let me know if this will save on gas compared to a @storage array
# MIT License

%builtins pedersen range_check

from starkware.cairo.common.alloc import alloc
from starkware.cairo.common.hash import hash2
from starkware.cairo.common.cairo_builtins import HashBuiltin
from starkware.cairo.common.math import unsigned_div_rem, split_felt, assert_nn, assert_le
from starkware.cairo.common.registers import get_fp_and_pc

# @member s the starting pointer of the vector
# @member e the ending pointer of the vector
# @member size the current size of the vector
struct vector:
    member s : felt*
    member e : felt*
    member size : felt
end

# @notice Appends {value} to the (e)nd of a vector. Increment the end pointer and size by 1 (SIZE of felt)
# @param v The vector which recieves the new element
# @param value The element that is added to the end of the vector
# @return A new vector containing the added element
func push{pedersen_ptr : HashBuiltin*, range_check_ptr}(v : vector, value : felt) -> (res : vector):
    let end_ptr = v.e
    [end_ptr] = value
    let new_v : vector = vector(v.s, end_ptr + 1, v.size + 1)
    return (new_v)
end

# @notice Retrieves the element at a given {index}
# @dev Will break if index is out of vector bounds
# @param v The vector
# @param index The index at which to get the desired value
# @return The value of the vector at an index
func at{pedersen_ptr : HashBuiltin*, range_check_ptr}(v : vector, index : felt) -> (res : felt):
    let res = v.s[index]
    return (res)
end

# @notice the drive function to demonstrate the vector
# @dev To run: cairo-compile ./contracts/vector.cairo --output ./artifacts/vector.json && cairo-run --program=./artifacts/vector.json --layout=all

func main{pedersen_ptr : HashBuiltin*, range_check_ptr}():
    alloc_locals
    let s : felt* = alloc()
    let e : felt* = s + 1
    let v : vector = vector(s, e, 4)

    let (v_2 : vector) = push(v, 1)
    let (res : vector) = push(v_2, 3)

    let ptr = res.e
    let val = [res.e - 1]
    %{ print(ids.ptr) %}
    %{ print(ids.val) %}

    let (val_at) = at(v_2, 2)
    assert 3 = val_at
    %{ print(ids.val_at) %}

    let (val_at) = at(v_2, 1)
    assert 1 = val_at
    %{ print(ids.val_at) %}

    return ()
end

Cheers! If I get rich using this, beer's on me 🍻