scheme_env.c

/*
  libscheme
  Copyright (c) 1994 Brent Benson
  All rights reserved.

  Permission is hereby granted, without written agreement and without
  license or royalty fees, to use, copy, modify, and distribute this
  software and its documentation for any purpose, provided that the
  above copyright notice and the following two paragraphs appear in
  all copies of this software.

  IN NO EVENT SHALL BRENT BENSON BE LIABLE TO ANY PARTY FOR DIRECT,
  INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
  OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF BRENT
  BENSON HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

  BRENT BENSON SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT
  NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER
  IS ON AN "AS IS" BASIS, AND BRENT BENSON HAS NO OBLIGATION TO
  PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR
  MODIFICATIONS.
*/

#include "scheme_private.h"
#include <ctype.h>

/* globals */
Scheme_Env *scheme_env;

/* locals */
static Scheme_Env *scheme_make_env (void);

Scheme_Env *
scheme_basic_env (void)
{
  Scheme_Env *env;

  /* The ordering of the first few init calls is important.
     Add to the end of the list, not the beginning. */
  env = scheme_make_env ();
  scheme_init_type (env);
  scheme_init_fun (env);
  scheme_init_symbol (env);
  scheme_init_list (env);
  scheme_init_number (env);
  scheme_init_port (env);
  scheme_init_string (env);
  scheme_init_vector (env);
  scheme_init_char (env);
  scheme_init_bool (env);
  scheme_init_syntax (env);
  scheme_init_eval (env);
  scheme_init_error (env);
  scheme_init_promise (env);
  scheme_init_struct (env);
  scheme_init_pointer (env);
  scheme_env = env;
  return (env);
}

static Scheme_Env *
scheme_make_env (void)
{
  Scheme_Env *env;

  env = (Scheme_Env *) scheme_malloc (sizeof (Scheme_Env));
  env->globals = scheme_make_hash_table (SCHEME_GLOBAL_BUCKETS);
  env->next = NULL;
  return (env);
}

void
scheme_add_global (char *name, Scheme_Value obj, Scheme_Env *env)
{
  char lower_name[SCHEME_MAX_SYM];
  int i;

  i = 0;
  while ( name[i] )
    {
      lower_name[i] = tolower (name[i]);
      i++;
    }
  lower_name[i] = '\0';
  scheme_add_to_table (env->globals, lower_name, obj);
}

void
scheme_add_prim (char *name, Scheme_Prim *prim, Scheme_Env *env)
{
  scheme_add_global(name, scheme_make_prim(prim), env);
}

Scheme_Env *
scheme_new_frame (int num_bindings)
{
  Scheme_Env *frame;

  frame = (Scheme_Env *) scheme_malloc (sizeof (Scheme_Env));
  frame->num_bindings = num_bindings;
  frame->symbols = (Scheme_Value *) scheme_malloc (num_bindings * sizeof (Scheme_Object*));
  frame->values = (Scheme_Value *) scheme_malloc (num_bindings * sizeof (Scheme_Object*));
  return (frame);
}

void
scheme_add_binding (int index, Scheme_Value sym, Scheme_Value val, Scheme_Env *frame)
{
  if ((index >= frame->num_bindings) || (index < 0))
    {
      scheme_signal_error ("internal error: scheme_add_binding() index out of range: %d", index);
    }
  frame->symbols[index] = sym;
  frame->values[index] = val;
}

Scheme_Env *
scheme_extend_env (Scheme_Env *frame, Scheme_Env *env)
{
  frame->globals = env->globals;
  frame->next = env;
  return (frame);
}

Scheme_Env *
scheme_add_frame (Scheme_Value syms, Scheme_Value vals, Scheme_Env *env)
{
  Scheme_Env *frame;
  int len, i;

  frame = (Scheme_Env *) scheme_malloc (sizeof (Scheme_Env));
  len = scheme_list_length (syms);
  frame->num_bindings = len;
  frame->symbols = (Scheme_Value *) scheme_malloc (len * sizeof (Scheme_Object*));
  frame->values = (Scheme_Value *) scheme_malloc (len * sizeof (Scheme_Object*));
  for ( i=0 ; i<len ; ++i )
    {
      if (SCHEME_SYMBOLP(syms))
	{
	  frame->symbols[i] = syms;
	  frame->values[i] = vals;
	}
      else
	{
	  frame->symbols[i] = SCHEME_CAR (syms);
	  frame->values[i] = SCHEME_CAR (vals);
	  syms = SCHEME_CDR (syms);
	  vals = SCHEME_CDR (vals);
	}
    }
  frame->globals = env->globals;
  frame->next = env;
  scheme_env = frame;
  return (frame);
}

Scheme_Env *
scheme_pop_frame (Scheme_Env *env)
{
  SCHEME_ASSERT ((env->next), "trying to pop a frame from an empty environment");
  scheme_env = env->next;
  return (env->next);
}

void
scheme_set_value (Scheme_Value symbol, Scheme_Value val, Scheme_Env *env)
{
  Scheme_Env *frame;

  frame = env;
  while ( frame->next != NULL )
    {
      int i;

      for ( i=0 ; i<frame->num_bindings ; ++i )
	{
	  if (symbol == frame->symbols[i])
	    {
	      frame->values[i] = val;
	      return;
	    }
	}
      frame = frame->next;
    }
  if (scheme_lookup_global (symbol, frame))
    {
      scheme_change_in_table (frame->globals, SCHEME_STR_VAL (symbol), val);
    }
  else
    {
      scheme_signal_error ("set!: var unbound: %s", SCHEME_STR_VAL(symbol));
    }
}

Scheme_Value
scheme_lookup_value (Scheme_Value symbol, Scheme_Env *env)
{
  Scheme_Env *frame;

  frame = env;
  while ( frame->next != NULL )
    {
      int i;

      for ( i=0 ; i<frame->num_bindings ; ++i )
	{
	  if (symbol == frame->symbols[i])
	    {
	      return (frame->values[i]);
	    }
	}
      frame = frame->next;
    }
  return (scheme_lookup_global (symbol, frame));
}

Scheme_Value
scheme_lookup_global (Scheme_Value symbol, Scheme_Env *env)
{
  return (scheme_lookup_in_table (env->globals, SCHEME_STR_VAL(symbol)));
}