/* --------
   MACROS: Four_Bit_Adder & Full_Adder
   -------- */

/* 
   Four_Bit_Adder

   Syntax: Four_Bit_Adder a[3..0] b[3..0] | Cout s[3..0];
   Effect: Adds binary numbers a + b with carry.
*/
Define Four_Bit_Adder a[3..0] b[3..0] | Co s[3..0];
 Full_Adder H1 a[3] b[3] Cc | Co s[3];
 Full_Adder H2 a[2] b[2] Cb | Cc s[2];
 Full_Adder H3 a[1] b[1] Ca | Cb s[1];
 Full_Adder H4 a[0] b[0] ZERO | Ca s[0];
Endef;

/* 
   Full adder.

   Syntax: Full_Adder a b c-in | c-out s;
   Effect: Adds binary numbers a + b with carry.
*/
Define Full_Adder a b CarryIn | CarryOut Sum;
  Xor aa a b x;
  Xor ab x CarryIn Sum;
  And bb a b y;
  And cb CarryIn x z;
  Or bc-cc y z CarryOut;
Endef;