#[derive(Debug, Clone)]
pub enum Instruction {
    Push(isize),
    Dup,
    CopyN(isize),
    Swap,
    Pop,
    PopN(isize),
    Add,
    Sub,
    Mul,
    Div,
    Mod,
    Store,
    Retrieve,
    DefineLabel(isize),
    CallAtLabel(isize),
    GotoLabel(isize),
    GotoLabelE0(isize),
    GotoLabelL0(isize),
    ReturnCallAt,
    End,
    StdOutChar,
    StdOutNum,
    StdInChar,
    StdInNum,
}