Last modified on Tue Mar 17 12:16:54 PST 1992 by muller modified on Wed Apr 12 09:23:40 1989 by kalsow

GENERIC INTERFACEA Rep.T w represents a sequence of Size bits w(0), ..., w(Size-1). It also represents the unsigned number sum of 2^(i) * w(i) for i in 0, ..., Size-1.GenWord (Rep);

TYPE T = Rep.T; (* encoding of T is implementation-dependent; e.g., 2's complement. *) CONST Size : INTEGER = BITSIZE (T); (* implementation-dependent *) PROCEDURE Plus (x, y: T): T; (* (x + y) MOD 2^[Word.Size] *) PROCEDURE Times (x, y: T): T; (* (x * y) MOD 2^[Word.Size] *) PROCEDURE Minus (x, y: T): T; (* (x - y) MOD 2^[Word.Size] *) PROCEDURE Divide (x, y: T): T; (* x divided by y *) PROCEDURE Mod (x, y: T): T; (* x MOD y *) PROCEDURE LT (x, y: T): BOOLEAN; (* x < y *) PROCEDURE LE (x, y: T): BOOLEAN; (* x <= y *) PROCEDURE GT (x, y: T): BOOLEAN; (* x > y *) PROCEDURE GE (x, y: T): BOOLEAN; (* x >= y *) PROCEDURE And (x, y: T): T; (* Bitwise AND of x and y *) PROCEDURE Or (x, y: T): T; (* Bitwise OR of x and y *) PROCEDURE Xor (x, y: T): T; (* Bitwise XOR of x and y *) PROCEDURE Not (x: T): T; (* Bitwise complement of x *) PROCEDURE Shift (x: T; n: INTEGER): T;

For all i such that both i and i - n are in the range [0 .. Word.Size - 1], bit i of the result equals bit i - n of x. The other bits of the result are 0. Thus, shifting by n > 0 is like multiplying by 2^(n)

PROCEDURE LeftShift (x: T; n: [0..Size-1]): T;

= Shift (x, n)

PROCEDURE RightShift (x: T; n: [0..Size-1]): T;

= Shift (x, -n)

PROCEDURE Rotate (x: T; n: INTEGER): T;

Bit i of the result equals bit (i - n) MOD Word.Size of x.

PROCEDURE LeftRotate (x: T; n: [0..Size-1]): T;

= Rotate (x, n)

PROCEDURE RightRotate (x: T; n: [0..Size-1]): T;

= Rotate (x, -n)

PROCEDURE Extract (x: T; i, n: CARDINAL): T;

Take n bits from x, with bit i as the least significant bit, and return them as the least significant n bits of a word whose other bits are 0. A checked runtime error if n + i > Word.Size.

PROCEDURE Insert (x, y: T; i, n: CARDINAL): T;

Return x with n bits replaced, with bit i as the least significant bit, by the least significant n bits of y. The other bits of x are unchanged. A checked runtime error if n + i > Word.Size.

END GenWord.