function digit的用法和样例：
例句
- A function is uniquely represented by a name and a set of operand types.
函数由函数名以及一组操作数类型唯一地表示。 - Based on sign digit negabinary representation, the two step addition and one step subtraction of arbitrary length operands can be performed.
基于符号数字负二进制表达，提出了任意字长操作数的并行两步加法与一步减法。
