Demonstration of array usage in cairo

louis.cairo

%builtins output

from starkware.cairo.common.alloc import alloc
from starkware.cairo.common.serialize import serialize_word

func print_array{output_ptr : felt*}(res_len : felt, res : felt*):
    if res_len == 0:
        return ()
    end

    serialize_word([res])
    print_array(res_len - 1, res + 1)
    return ()
end

func fill_array(arr : felt*, size : felt) -> ():
    if size == 0:
        return ()
    else:
        assert [arr] = size
        return fill_array(arr + 1, size - 1)
    end
end

func main{output_ptr : felt*}():
    const FILL_SIZE = 2

    alloc_locals
    # Allocate an array.
    let (ptr) = alloc()

    # Populate some values in the array.
    assert [ptr] = 32
    assert [ptr + 1] = 64

    # fill the array
    fill_array(arr=ptr + 2, size=FILL_SIZE)

    # the line that requires alloc_locals because ptr was revoked
    print_array(2 + FILL_SIZE, ptr)
    return ()
end