Function erlang_nif_sys::erlang_nif_sys_api::enif_get_double

pub unsafe extern "C" fn enif_get_double(
    arg1: *mut ErlNifEnv, 
    term: ERL_NIF_TERM, 
    dp: *mut c_double
) -> c_int

See enif_get_double in the Erlang docs.