clean up case statements and math

src/ada_chip.adb

@@ -50,11 +50,10 @@ procedure Ada_Chip is
       case ins.Value is
          when ISA.Clear_Screen => Video.Clear_Screen;
          when ISA.Ret => CPU.Ret (State);
-         when others => begin
+         when others =>
             Ada.Text_IO.Put_Line ("Machine code calls are unsupported!");
             delay 1.0;
             Video.Finish;
-         end;
       end case;
    end Run_Flow;
 
@@ -90,14 +89,13 @@ procedure Ada_Chip is
             State.Address_Register + Address (State.Registers (X));
          when Get_Font =>
             State.Address_Register := Address (State.Registers (X) mod 16) * 5;
-         when Get_BCD => begin
+         when Get_BCD =>
             State.Memory (State.Address_Register) :=
                State.Registers (X) / 100;
             State.Memory (State.Address_Register + 1) :=
                State.Registers (X) / 10 mod 10;
             State.Memory (State.Address_Register + 2) :=
                State.Registers (X) mod 10;
-         end;
       end case;
    end Run_Misc;
 

src/cpu.adb

@@ -1,5 +1,4 @@
 with Ada.Sequential_IO;
-with Ada.Text_IO;
 with Bit_Ops;
 
 package body CPU is
@@ -52,47 +51,32 @@ package body CPU is
    end Skip;
 
    procedure Math (Inst : in out Instance; VX, VY : Register_Index; N : Byte)
-   is begin
+   is
-      case N is
-         when 0 =>
-            Inst.Registers (VX) := Inst.Registers (VY);
-         when 1 =>
-            Inst.Registers (VX) := Bit_Ops.Bitwise_Or
-               (Inst.Registers (VX), Inst.Registers (VY));
-         when 2 =>
-            Inst.Registers (VX) := Bit_Ops.Bitwise_And
-               (Inst.Registers (VX), Inst.Registers (VY));
-         when 3 =>
-            Inst.Registers (VX) := Bit_Ops.Bitwise_Xor
-               (Inst.Registers (VX), Inst.Registers (VY));
-         when 4 =>
-            declare
       X : constant Byte := Inst.Registers (VX);
       Y : constant Byte := Inst.Registers (VY);
    begin
+      case Math_Class'Enum_Val (N) is
+         when Assign => Inst.Registers (VX) := Y;
+         when Bit_Or => Inst.Registers (VX) := Bit_Ops.Bitwise_Or (X, Y);
+         when Bit_And => Inst.Registers (VX) := Bit_Ops.Bitwise_And (X, Y);
+         when Bit_Xor => Inst.Registers (VX) := Bit_Ops.Bitwise_Xor (X, Y);
+         when Add =>
             Inst.Registers (VX) := X + Y;
             Inst.Registers (15) :=
                (if Integer (X) + Integer (Y) > Integer (X + Y)
                   then 1 else 0);
-            end;
+         when Sub_Y =>
-         when 5 =>
-            declare
-               X : constant Byte := Inst.Registers (VX);
-               Y : constant Byte := Inst.Registers (VY);
-            begin
             Inst.Registers (VX) := X - Y;
             Inst.Registers (15) := (if X >= Y then 1 else 0);
-            end;
+         when Shift_Right =>
-         when 6 =>
+            Inst.Registers (15) := X mod 2;
-            Inst.Registers (15) := Inst.Registers (VX) mod 2;
+            Inst.Registers (VX) := X / 2;
-            Inst.Registers (VX) := Inst.Registers (VX) / 2;
+         when Sub_X =>
-         when 14 =>
+            Inst.Registers (VX) := Y - X;
-            Inst.Registers (15) := Inst.Registers (VX) / (2 ** 7);
+            Inst.Registers (15) := (if Y >= X then 1 else 0);
-            Inst.Registers (VX) := Inst.Registers (VX) * 2;
+         when Shift_Left =>
-         when others => begin
+            Inst.Registers (15) := X / (2 ** 7);
-            Ada.Text_IO.Put_Line ("Uh oh!");
+            Inst.Registers (VX) := X * 2;
-            Ada.Text_IO.Put_Line (Byte'Image (N));
-         end;
       end case;
    end Math;
 

src/isa.ads

@@ -46,6 +46,23 @@ package ISA is
    Clear_Screen : constant Opcode_Value := 16#E0#;
    Ret          : constant Opcode_Value := 16#EE#;
 
+   type Math_Class is (
+      Assign, Bit_Or, Bit_And, Bit_Xor, Add, Sub_Y, Shift_Right, Sub_X,
+      Shift_Left
+   );
+
+   for Math_Class use (
+      Assign      => 0,
+      Bit_Or      => 1,
+      Bit_And     => 2,
+      Bit_Xor     => 3,
+      Add         => 4,
+      Sub_Y       => 5,
+      Shift_Right => 6,
+      Sub_X       => 7,
+      Shift_Left  => 14
+   );
+
    type Input_Class is (Key_Down, Key_Up);
 
    for Input_Class use (