(* ========================================================= *)
  (* Preliminary library module for Gardens Point Modula       *)
  (* ========================================================= *)

(* !SYSTEM! *) DEFINITION MODULE $SYSTEM$;

  (* This is a system module; it is known to the compiler and  *)
  (* activated by import. It is pre-loaded, and thus has no    *)
  (* symbol file. Some of the following declarations are sym-  *)
  (* bolic only and use generic forms which cannot be compiled *)
  (* The system types have special semantics in most cases.    *)

  TYPE  SAL  = "smallest addressable unit";
	BIN  = [0 .. 31]; (* BITSET = SET OF BIN *)
	WORD = "natural word size";
	BYTE = SAL;
	ADDRESS = POINTER TO SAL;

  PROCEDURE ADR   (VAR v : AnyType) : ADDRESS;
  (* returns storage address of the parameter *)

  PROCEDURE INCADR(a : ADDRESS; i : CARDINAL) : ADDRESS;
  (* returns the address a "incremented" by i *)

  PROCEDURE DECADR(a : ADDRESS; d : CARDINAL) : ADDRESS;
  (* returns the address a "decremented" by i *)

  PROCEDURE DIFADR(a, b : ADDRESS) : INTEGER;
  (* returns the difference (a - b) in bytes  *)

  PROCEDURE TSIZE (AnyType; optional tags) : CARDINAL;
  (* returns storage size of t, ignoring tags *)

  PROCEDURE CAST  (AnyType1; x : AnyType2) : AnyType1;
  (* returns x cast to type AnyType1, if poss *)
  (* ! there are some hardware restrictions ! *)

  PROCEDURE SHIFT (VAR b : BITSET, n : INTEGER);
  PROCEDURE ROTATE(VAR b : BITSET; n : INTEGER);
  (* the direction of shifts and rotates is   *)
  (* such that
	b := BITSET{0};
	SHIFT(b,1);
     leaves b = BITSET{1}, rotate is same     *)

  PROCEDURE CALL(callBody : AnyProcType;
		 ... args for body if needed ...
		 onError  : Exceptions.RecoveryProc);
  (* semantics are as for Exceptions.Call, except  *)
  (* that parameters may be passed to the callBody *)
  
END SYSTEM.