juno-machine/src/JunoArgs.i3

 Copyright (C) 1992, Digital Equipment Corporation                         
 All rights reserved.                                                      
 See the file COPYRIGHT for a full description.                            
                                                                           
 Last modified on Fri Jun 30 20:37:17 PDT 1995 by heydon                   
      modified on Fri Jul 17 17:20:47 PDT 1992 by myers                    


INTERFACE JunoArgs;

IMPORT RTVal, JunoValue;

 JunoArgs provides an interface to the Juno runtime stack that is
   useful for implementing external Modula-3 procedures. These procedures
   allow clients to read and write a procedure's actual arguments.


   Where possible, the procedures in this interface convert between the
   RTVal.T's on the machine's run-time stack and Modula-3 types like
   INTEGER, REAL, and TEXT. 


PROCEDURE ReadValue(i: CARDINAL): RTVal.T;

 Return the parameter with index -i. Usually, the parameter is expected to
   have a particular type, in which case one of the ReadX procedures below
   should be used. 

PROCEDURE ReadInt(i: CARDINAL; VAR err: BOOLEAN): INTEGER;
PROCEDURE ReadReal(i: CARDINAL; VAR err: BOOLEAN): JunoValue.Real;
PROCEDURE ReadText(i: CARDINAL; VAR err: BOOLEAN): TEXT;
PROCEDURE ReadPair(i: CARDINAL; VAR err: BOOLEAN): RTVal.Pair;

 Read the actual parameter of the specified type with index -i. If the
   value at position -i in the stack frame is not the correct type, set
   err to TRUE and return an undefined value. Otherwise, leave err
   unchanged. The ReadInt procedure expects to find a real number, and
   returns the result of rounding that real value to the nearest integer. 


PROCEDURE WriteValue(i: CARDINAL; val: RTVal.T);

 Write the value val as the result parameter with index -i. 

PROCEDURE WriteInt(i: CARDINAL; int: INTEGER);
PROCEDURE WriteReal(i: CARDINAL; r: JunoValue.Real);
PROCEDURE WriteText(i: CARDINAL; t: TEXT);

 Equivalent to: WriteValue(i, RTVal.FromInt(int)), WriteValue(i,
   RTVal.FromReal(r)), and WriteValue(i, RTVal.FromText(t)). 

PROCEDURE PushValue(v: RTVal.T);

 Push v onto the runtime stack. Requires v # NIL. 

END JunoArgs.





interface JunoValue is in: