INTERFACE Extended;
IMPORT Word;

This package defines some basic properties of the built-in float type EXTENDED.

Index: EXTENDED; floating-point; generics

TYPE T = EXTENDED;

CONST
  Base: INTEGER = 2;
  (* The radix of the floating-point representation for T *)

  Precision: INTEGER = 53;
  (* The number of digits of precision in the given Base for T. *)

  MaxFinite: T = 1.7976931348623157X+308;
  (* The maximum finite value in T.  For non-IEEE implementations,
     this is the same as LAST(T). *)

  MinPos: T = 4.9406564584124654X-324;
  (* The minimum positive value in T. *)

  MinPosNormal: T = 2.2250738585072014X-308;
  (* The minimum positive "normal" value in T; differs from MinPos
     only for implementations with denormalized numbers. *)

CONST
  MaxExpDigits = 3;
  MaxSignifDigits = 17;

MaxExpDigits is the smallest integer with the property that every finite number of type T can be written in base-10 scientific notation using an exponent with at most MaxExpDigits. MaxSignifDigits is the smallest integer with the property that floating-decimal numbers with MaxSignifDigits are more closely spaced, all along the number line, than are numbers of type T. Typically,

      MaxExpDigits    = ceiling(log_10(log_10(MaxFinite)))
      MaxSignifDigits = ceiling(log_10(Base^Precision)) + 1.


CONST Brand = "Extended";

PROCEDURE Equal(a, b: T): BOOLEAN;
 Return a = b.  The result is undefined if either a or b is
   an NaN (not a number) value. 

PROCEDURE Hash(a: T): Word.T;
 Return a hash value derived from a.  The result is undefined if
   either a or b is an NaN (not a number) value. 

PROCEDURE Compare(a, b: T): [-1..1];
 Return -1 if a < b, 0 if a = b, or +1 if a > b.
   The result is undefined if either a or b is an NaN (not a
   number) value. 

END Extended.