Ada中Z80仿真器中的类型转换太多

Question

我正在Ada做一个Z80模拟器.我正在实现JR(Jump relative)系列,但我对我的代码不满意:

with Ada.Text_IO;

procedure main is
    type UInt16 is mod 2 ** 16;
    type UInt8  is mod 2 **  8;
    type Int8   is range -128 .. 127;

    package UInt16_IO is new Ada.Text_IO.Modular_IO (UInt16);

    function Two_Complement(N : UInt8) return Int8 is
    begin
        if N <= 127 then
            return Int8 (N);
        end if;
        return Int8 (Integer (N) - 256);
    end Two_Complement;

    -- Relative jump
    function Jr (Address : UInt16; D: UInt8) return UInt16 is
    begin
        return UInt16 (Integer (Address) + Integer (Two_Complement (D) + 2));
    end Jr;

    Address : UInt16;
begin
    Address := 16#683#;
    UInt16_IO.Put (Item => Jr (Address, 16#F1#), Base => 16); -- Get    16#676# which is good !
end main;

它似乎有效,但我发现有太多类型的转换.你有什么建议吗？

谢谢,

奥利维尔.

Answer 1

你可以看看

function Jr (Address : UInt16; D: UInt8) return UInt16 is
   Offset : constant Uint16
     := Uint16 (D) + (if D >= 16#80# then 16#ff00# else 0);
begin
   return Address + Offset + 2;
end Jr;

但它取决于你需要发生什么 - 例如 - 地址是0而D是,比方说,16#80(上面的代码返回16#ff82#).