INTERFACE BigIntegerRep;

Arithmetic for Modula-3, see doc for details

Concrete type of Value and implementation of unsigned arithmetic.

IMPORT Word AS W;
IMPORT BigInteger AS BI;
FROM Arithmetic IMPORT Error;

REVEAL BI.Value = BRANDED "BigIntegerValue" REF ARRAY OF W.T;

TYPE
  Value = BI.Value;
  T = BI.T;
  QuotRem = BI.QuotRem;

PROCEDURE Clear ( (*OUT*)v: Value; );

PROCEDURE MinMax (VAR min, max: INTEGER; a, b: INTEGER; );
PROCEDURE CorrectSize (VAR x: T; start: INTEGER; );
PROCEDURE AddU (READONLY x, y: T; ): T;
PROCEDURE SubU (READONLY x, y: T; ): T;
PROCEDURE CompareU (READONLY x, y: T; ): [-1 .. 1];
PROCEDURE MulU (READONLY x, y: T; ): T;
PROCEDURE DivModU (x, y: T; ): QuotRem RAISES {Error};

TYPE
  BitPos = RECORD
             word: INTEGER;
             bit : [0 .. W.Size - 1];
           END;

PROCEDURE AddBitPos (READONLY x, y: BitPos; ):
  BitPos;                        (* only for testing *)
PROCEDURE SubBitPos (READONLY x, y: BitPos; ): BitPos;
PROCEDURE CompareBitPos (READONLY x, y: BitPos; ): [-1 .. 1];
PROCEDURE BitPosEndToBegin (READONLY x: BitPos; ): BitPos;
PROCEDURE GetMSBPos (READONLY x: T; ): BitPos;
PROCEDURE GetSubword (READONLY x: T; sh: BitPos; ): W.T;
PROCEDURE SubShiftedProd (VAR x: T; READONLY y: T; z: W.T; sh: BitPos; );
PROCEDURE AddShifted (VAR x: T; y: W.T; sh: BitPos; );

END BigIntegerRep.