HashBuiltin - Cairo

Question

I am having this contract.cairo:3:59: Unknown identifier 'HashBuiltin' after doing :

starknet-compile contract.cairo
--output contract_compiled.json
--abi contract_abi.json

代码 ：

@external
func increase_balance{syscall_ptr : felt*, pedersen_ptr : HashBuiltin*, range_check_ptr}(
        amount : felt):
    let (res) = balance.read()
    balance.write(res + amount)
    return ()
end

# Returns the current balance.
@view
func get_balance{syscall_ptr : felt*, pedersen_ptr : HashBuiltin*, range_check_ptr}() -> (
        res : felt):
    let (res) = balance.read()
    return (res=res)
end

任何解释？

Answer 1

I forgot to add

from starkware.cairo.common.cairo_builtins import HashBuiltin

Answer 2

You have to add this line to import it from Cairo libraries.

from starkware.cairo.common.cairo_builtins import HashBuiltin

That should do the trick.