(int, int, int, int) compute_data_size?(cell c, int max_cells) pure asm "CDATASIZEQ NULLSWAPIFNOT2 NULLSWAPIFNOT";
builder begin_cell() pure asm "NEWC";
cell end_cell(builder b) pure asm "ENDC";

(int, int) validate_input(cell input) pure {
    var (x, y, z, correct) = compute_data_size?(input, 10);
    throw_unless(102, correct);
}

int main() pure {
    cell c = begin_cell().end_cell();
    validate_input(c);
    return 0;
}

{-
@compilation_should_fail
@stderr
"""
An impure operation in a pure function
throw_unless
"""
-}