#ifndef ___ENV
#define ___ENV

#include "fundls.hpp"
#include "functs.hpp"

// A class for activation records.  A name field is provided solely
//   for debugging purposes.  Control links and activation links are
//   provided.  Activation records must also contain the values bound
//   both the parameters and function names used by the function being
//   activated.
// There are two constructors:  one for a top-level call, and one for
//   all other calls.

class function;
class list_of_offsets;
class list_of_functions;

class activation						{
friend environment;
protected:
  char *name;             // just for debugging
  activation *control;
  activation *access;
  list_of_offsets *actuals;
  list_of_functions *functs;
public:
  activation(void);
  activation(function *);					    };


// An environment object is just a linked list of activation records.
//   Since these records are linked both by control links and by
//   activation links, the links are stored in the activation records,
//   so that the only member object of an environment object is a
//   pointer to the first activation record.
// Nonetheless, many useful functions may be treated as member functions
//   of the "environment" class, e.g., the functions that "push" and
//   "pop" activation records to or from the environment.  Another
//   example is the function that runs a compiled "program".  Actually
//   there are two such functions -- one that handles a top level function
//   (taking a pointer to a function object as parameter) and one that
//   handles all other functions.
// Other member functions look up the bodies of functions in the
//   environment, look up the values of variables in the
//   environment, and bind formals to actuals in the environment.

class environment							{
protected:
  activation *first;
public:
  environment(void);
  void push(activation *, int);
  void pop();
  void run(function *);
  void run(list_of_offsets *, function *);
  function *get_function(offset *);
  offset *eval(offset *);
  void bind(list_of_offsets *, list_of_offsets *);			};


#endif