DEFINITION MODULE LargeNumbers;

(* Handle very large numbers *)
(* V3.0, J. Andrea, Nov.14/92 *)

EXPORT QUALIFIED NumType, zero, one,
                 StatusType, status,
                 SetDigits, Add, Subtract, Multiply, Divide,
                 Abs, ChangeSign,
                 Times10, Divide10,
                 StringToNum, NumToString;

CONST
   max_precision = 200;
   min_exp = -16000;
   max_exp =  16000;
   
TYPE
   SignType = (positive,negative);
   NumType  = RECORD
               man  :ARRAY [-1..max_precision] OF CHAR;   (* mantissa *)
               sign :SignType;  (* sign of mantissa *)
               exp  :INTEGER;   (* exponent, may be positive or negative *)
               an   :CARDINAL;  (* a number, set when each number is initialized *)
              END;
   StatusType = ( ok, overflow, underflow, divide_by_zero,
                  too_few_digits, too_many_digits, invalid_digit,
                  nan );  (* Not A Number *)
                  
VAR
  status :StatusType;
  zero, one :NumType;

PROCEDURE SetDigits( d :INTEGER );

PROCEDURE Add( a, b :NumType; VAR c :NumType );
PROCEDURE Subtract( a, b :NumType; VAR c :NumType );
PROCEDURE Multiply( a, b :NumType; VAR c :NumType );
PROCEDURE Divide( a, b :NumType; VAR c :NumType );

PROCEDURE Abs( VAR a :NumType );
PROCEDURE ChangeSign( VAR a :NumType );

PROCEDURE Times10( VAR a :NumType );
PROCEDURE Divide10( VAR a :NumType );
(* Times10 and Divide10 are fast operators *)
 
PROCEDURE StringToNum( s :ARRAY OF CHAR; VAR a :NumType );
PROCEDURE NumToString( a :NumType; VAR s :ARRAY OF CHAR );

END LargeNumbers.