cvs/stack/stack.c

/* printf */
#include <stdio.h>
/* EXIT_SUCCESS */
#include <stdlib.h>
/* NULL */
#include <stddef.h>
/* dlopen, dlsym, dlerror */
#include <dlfcn.h>
/* assert */
#include <assert.h>

#define HASHTBLSIZE 65536

/* First, define some types. */

/* A value of some type */
typedef struct {
  enum {
    integer,
    string,
    ref,                        /* Reference (to an element in the
                                   hash table) */
    func,                       /* Function pointer */
    symb, 
    list
  } type;                       /* Type of stack element */

  union {
    void *ptr;                  /* Pointer to the content */
    int val;                    /* ...or an integer */
  } content;                    /* Stores a pointer or an integer */

  int refcount;                 /* Reference counter */

} value;

/* A symbol with a name and possible value */
/* (These do not need reference counters, they are kept unique by
   hashing.) */
typedef struct symbol_struct {
  char *id;                     /* Symbol name */
  value *val;                   /* The value (if any) bound to it */
  struct symbol_struct *next;   /* In case of hashing conflicts, a */
} symbol;                       /* symbol is a kind of stack item. */

/* A type for a hash table for symbols */
typedef symbol *hashtbl[HASHTBLSIZE]; /* Hash table declaration */

/* An item (value) on a stack */
typedef struct stackitem_struct
{
  value *item;                  /* The value on the stack */
  struct stackitem_struct *next; /* Next item */
} stackitem;

/* An environment; gives access to the stack and a hash table of
   defined symbols */
typedef struct {
  stackitem *head;              /* Head of the stack */
  hashtbl symbols;              /* Hash table of all variable bindings */
  int err;                      /* Error flag */
} environment;

/* A type for pointers to external functions */
typedef void (*funcp)(environment *); /* funcp is a pointer to a void
                                         function (environment *) */

/* Initialize a newly created environment */
void init_env(environment *env)
{
  long i;

  for(i= 0; i<HASHTBLSIZE; i++)
    env->symbols[i]= NULL;
}

/* Returns a pointer to a pointer to an element in the hash table. */
symbol **hash(hashtbl in_hashtbl, const char *in_string)
{
  long i= 0;
  unsigned long out_hash= 0;
  char key= '\0';
  symbol **position;
  
  while(1){                     /* Hash in_string */
    key= in_string[i++];
    if(key=='\0')
      break;
    out_hash= out_hash*32+key;
  }

  out_hash= out_hash%HASHTBLSIZE;
  position= &(in_hashtbl[out_hash]);

  while(1){
    if(*position==NULL)         /* If empty */
      return position;
    
    if(strcmp(in_string, (*position)->id)==0) /* If match */
      return position;

    position= &((*position)->next); /* Try next */
  }
}

/* Generic push function. */
int push(stackitem** stack_head, stackitem* in_item)
{
  in_item->next= *stack_head;
  *stack_head= in_item;
  return 1;
}

/* Push a value onto the stack */
void push_val(stackitem **stack_head, value *val)
{
  stackitem *new_item= malloc(sizeof(stackitem));
  new_item->item= val;
  val->refcount++;
  push(stack_head, new_item);
}

/* Push an integer onto the stack. */
int push_int(stackitem **stack_head, int in_val) 
{
  value *new_value= malloc(sizeof(value));
  stackitem *new_item= malloc(sizeof(stackitem));
  new_item->item= new_value;
  
  new_value->content.val= in_val;
  new_value->type= integer;
  new_value->refcount=1;

  push(stack_head, new_item);
  return 1;
}

/* Copy a string onto the stack. */
int push_cstring(stackitem **stack_head, const char *in_string)
{
  value *new_value= malloc(sizeof(value));
  stackitem *new_item= malloc(sizeof(stackitem));
  new_item->item=new_value;

  new_value->content.ptr= malloc(strlen(in_string)+1);
  strcpy(new_value->content.ptr, in_string);
  new_value->type= string;
  new_value->refcount=1;

  push(stack_head, new_item);
  return 1;
}

/* Push a symbol onto the stack. */
int push_sym(environment *env, const char *in_string)
{
  stackitem *new_item;          /* The new stack item */
  /* ...which will contain... */
  value *new_value;             /* A new symbol value */
  /* ...which might point to... */
  symbol **new_symbol;          /* (if needed) A new actual symbol */
  /* ...which, if possible, will be bound to... */
  value *new_fvalue;            /* (if needed) A new function value */
  /* ...which will point to... */
  void *funcptr;                /* A function pointer */

  static void *handle= NULL;    /* Dynamic linker handle */

  /* Create a new stack item containing a new value */
  new_item= malloc(sizeof(stackitem));
  new_value= malloc(sizeof(value));
  new_item->item=new_value;

  /* The new value is a symbol */
  new_value->type= symb;
  new_value->refcount= 1;

  /* Look up the symbol name in the hash table */
  new_symbol= hash(env->symbols, in_string);
  new_value->content.ptr= *new_symbol;

  if(*new_symbol==NULL) { /* If symbol was undefined */

    /* Create a new symbol */
    (*new_symbol)= malloc(sizeof(symbol));
    (*new_symbol)->val= NULL;   /* undefined value */
    (*new_symbol)->next= NULL;
    (*new_symbol)->id= malloc(strlen(in_string)+1);
    strcpy((*new_symbol)->id, in_string);

    /* Intern the new symbol in the hash table */
    new_value->content.ptr= *new_symbol;

    /* Try to load the symbol name as an external function, to see if
       we should bind the symbol to a new function pointer value */
    if(handle==NULL)            /* If no handle */
      handle= dlopen(NULL, RTLD_LAZY);

    funcptr= dlsym(handle, in_string); /* Get function pointer */
    if(dlerror()==NULL) {       /* If a function was found */
      new_fvalue= malloc(sizeof(value)); /* Create a new value */
      new_fvalue->type=func;    /* The new value is a function pointer */
      new_fvalue->content.ptr=funcptr; /* Store function pointer */
      (*new_symbol)->val= new_fvalue; /* Bind the symbol to the new
                                         function value */
      new_fvalue->refcount= 1;
    }
  }
  push(&(env->head), new_item);
  return 1;
}

void printerr(const char* in_string) {
  fprintf(stderr, "Err: %s\n", in_string);
}

/* Throw away a value */
void free_val(value *val){
  stackitem *item, *temp;

  val->refcount--;              /* Decrease the reference count */
  if(val->refcount == 0){
    switch (val->type){         /* and free the contents if necessary */
    case string:
      free(val->content.ptr);
    case list:                  /* lists needs to be freed recursively */
      item=val->content.ptr;
      while(item != NULL) {     /* for all stack items */
        free_val(item->item);   /* free the value */
        temp=item->next;        /* save next ptr */
        free(item);             /* free the stackitem */
        item=temp;              /* go to next stackitem */
      }
      free(val);                /* Free the actual list value */
      break;
    default:
      break;
    }
  }
}

/* Discard the top element of the stack. */
extern void toss(environment *env)
{
  stackitem *temp= env->head;

  if((env->head)==NULL) {
    printerr("Stack empty");
    return;
  }
  
  free_val(env->head->item);    /* Free the value */
  env->head= env->head->next;   /* Remove the top stack item */
  free(temp);                   /* Free the old top stack item */
}

/* Print newline. */
extern void nl()
{
  printf("\n");
}

/* Prints the top element of the stack. */
void print_h(stackitem *stack_head)
{

  if(stack_head==NULL) {
    printerr("Stack empty");
    return;
  }

  switch(stack_head->item->type) {
  case integer:
    printf("%d", stack_head->item->content.val);
    break;
  case string:
    printf("\"%s\"", (char*)stack_head->item->content.ptr);
    break;
  case symb:
    printf("'%s'", ((symbol *)(stack_head->item->content.ptr))->id);
    break;
  default:
    printf("%p", (funcp)(stack_head->item->content.ptr));
    break;
  }
}

extern void print_(environment *env) {
  print_h(env->head);
}

/* Prints the top element of the stack and then discards it. */
extern void print(environment *env)
{
  print_(env);
  toss(env);
}

/* Only to be called by function printstack. */
void print_st(stackitem *stack_head, long counter)
{ 
  if(stack_head->next != NULL)
    print_st(stack_head->next, counter+1);
  printf("%ld: ", counter);
  print_h(stack_head);
  nl();
}


/* Prints the stack. */
extern void printstack(environment *env)
{
  if(env->head != NULL) {
    print_st(env->head, 1);
    nl();
  } else {
    printerr("Stack empty");
  }
}

/* Swap the two top elements on the stack. */
extern void swap(environment *env)
{
  stackitem *temp= env->head;
  
  if((env->head)==NULL) {
    printerr("Stack empty");
    return;
  }

  if(env->head->next==NULL) {
    printerr("Not enough arguments");
    return;
  }

  env->head= env->head->next;
  temp->next= env->head->next;
  env->head->next= temp;
} 

stackitem* copy(stackitem* in_item)
{
  stackitem *out_item= malloc(sizeof(stackitem));

  memcpy(out_item, in_item, sizeof(stackitem));
  out_item->next= NULL;

  return out_item;
}

/* Recall a value from a symbol, if bound */
extern void rcl(environment *env)
{
  value *val;

  if(env->head == NULL) {
    printerr("Stack empty");
    return;
  }

  if(env->head->item->type!=symb) {
    printerr("Not a symbol");
    return;
  }
  val=((symbol *)(env->head->item->content.ptr))->val;
  if(val == NULL){
    printerr("Unbound variable");
    return;
  }
  toss(env);            /* toss the symbol */
  push_val(&(env->head), val); /* Return its bound value */
}

/* If the top element is a symbol, determine if it's bound to a
   function value, and if it is, toss the symbol and execute the
   function. */
extern void eval(environment *env)
{
  funcp in_func;
  value* val;
  if(env->head==NULL) {
    printerr("Stack empty");
    return;
  }

  /* if it's a symbol */
  if(env->head->item->type==symb) {

    /* If it's not bound to anything */
    if (((symbol *)(env->head->item->content.ptr))->val == NULL) {
      printerr("Unbound variable");
      return;
    }
    
    /* If it contains a function */
    if (((symbol *)(env->head->item->content.ptr))->val->type == func) {
      in_func=
        (funcp)(((symbol *)(env->head->item->content.ptr))->val->content.ptr);
      toss(env);
      (*in_func)(env);          /* Run the function */
      return;
    } else {                    /* If it's not a function */
      val=((symbol *)(env->head->item->content.ptr))->val;
      toss(env);                /* toss the symbol */
      push_val(&(env->head), val); /* Return its bound value */
    }
  }

  /* If it's a lone function value, run it */
  if(env->head->item->type==func) {
    in_func= (funcp)(env->head->item->content.ptr);
    toss(env); 
    (*in_func)(env);
    return;
  }

}

/* Make a list. */
extern void pack(environment *env)
{
  void* delimiter;
  stackitem *iterator, *temp;
  value *pack;

  delimiter= env->head->item->content.ptr; /* Get delimiter */
  toss(env);

  iterator= env->head;

  if(iterator==NULL || iterator->item->content.ptr==delimiter) {
    temp= NULL;
    toss(env);
  } else {
    /* Search for first delimiter */
    while(iterator->next!=NULL
          && iterator->next->item->content.ptr!=delimiter)
      iterator= iterator->next;
    
    /* Extract list */
    temp= env->head;
    env->head= iterator->next;
    iterator->next= NULL;
    
    if(env->head!=NULL)
      toss(env);
  }

  /* Push list */
  pack= malloc(sizeof(value));
  pack->type= list;
  pack->content.ptr= temp;
  pack->refcount= 1;

  temp= malloc(sizeof(stackitem));
  temp->item= pack;

  push(&(env->head), temp);
}

/* Parse input. */
int stack_read(environment *env, char *in_line) 
{
  char *temp, *rest;
  int itemp;
  size_t inlength= strlen(in_line)+1;
  int convert= 0;
  static int non_eval_flag= 0;

  temp= malloc(inlength);
  rest= malloc(inlength);

  do {
    /* If string */
    if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
      push_cstring(&(env->head), temp);
      break;
    }
    /* If integer */
    if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
      push_int(&(env->head), itemp);
      break;
    }
    /* Escape ';' with '\' */
    if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
      temp[1]= '\0';
      push_sym(env, temp);
      break;
    } 
    /* If symbol */
    if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
        push_sym(env, temp);
        break;
    }
    /* If single char */
    if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
      if(*temp==';') {
        if(!non_eval_flag) {
          eval(env);            /* Evaluate top element */
          break;
        }
        
        push_sym(env, ";");
        break;
      }

      if(*temp==']') {
        push_sym(env, "[");
        pack(env);
        if(non_eval_flag!=0)
          non_eval_flag--;
        break;
      }

      if(*temp=='[') {
        push_sym(env, "[");
        non_eval_flag++;
        break;
      }
    }
  } while(0);


  free(temp);

  if(convert<2) {
    free(rest);
    return 0;
  }
   
  stack_read(env, rest);
  
  free(rest);
  return 1;
}

/* Relocate elements of the list on the stack. */
extern void expand(environment *env)
{
  stackitem *temp, *new_head;

  /* Is top element a list? */
  if(env->head==NULL || env->head->item->type!=list) {
    printerr("Stack empty or not a list");
    return;
  }

  /* The first list element is the new stack head */
  new_head= temp= env->head->item->content.ptr;

  env->head->item->refcount++;
  toss(env);

  /* Find the end of the list */
  while(temp->next!=NULL)
    temp= temp->next;

  /* Connect the tail of the list with the old stack head */
  temp->next= env->head;
  env->head= new_head;          /* ...and voila! */

}

/* Compares two elements by reference. */
extern void eq(environment *env)
{
  void *left, *right;
  int result;

  if((env->head)==NULL || env->head->next==NULL) {
    printerr("Not enough elements to compare");
    return;
  }

  left= env->head->item->content.ptr;
  swap(env);
  right= env->head->item->content.ptr;
  result= (left==right);
  
  toss(env); toss(env);
  push_int(&(env->head), result);
}

/* Negates the top element on the stack. */
extern void not(environment *env)
{
  int val;

  if((env->head)==NULL || env->head->item->type!=integer) {
    printerr("Stack empty or element is not a integer");
    return;
  }

  val= env->head->item->content.val;
  toss(env);
  push_int(&(env->head), !val);
}

/* Compares the two top elements on the stack and return 0 if they're the
   same. */
extern void neq(environment *env)
{
  eq(env);
  not(env);
}

/* Give a symbol some content. */
extern void def(environment *env)
{
  symbol *sym;

  /* Needs two values on the stack, the top one must be a symbol */
  if(env->head==NULL || env->head->next==NULL 
     || env->head->item->type!=symb) {
    printerr("Define what?");
    return;
  }

  /* long names are a pain */
  sym=env->head->item->content.ptr;

  /* if the symbol was bound to something else, throw it away */
  if(sym->val != NULL)
    free_val(sym->val);

  /* Bind the symbol to the value */
  sym->val= env->head->next->item;
  sym->val->refcount++;         /* Increase the reference counter */

  toss(env); toss(env);
} 

/* Quit stack. */
extern void quit(environment *env)
{
  exit(EXIT_SUCCESS);
}

/* Clear stack */
extern void clear(environment *env)
{
  while(env->head!=NULL)
    toss(env);
}

/* List all defined words */
extern void words(environment *env)
{
  symbol *temp;
  int i;
  
  for(i= 0; i<HASHTBLSIZE; i++) {
    temp= env->symbols[i];
    while(temp!=NULL) {
      printf("%s\n", temp->id);
      temp= temp->next;
    }
  }
}

/* Forgets a symbol (remove it from the hash table) */
extern void forget(environment *env)
{
  char* sym_id;
  stackitem *stack_head= env->head;
  symbol **hash_entry, *temp;

  if(stack_head==NULL || stack_head->item->type!=symb) {
    printerr("Stack empty or not a symbol");
    return;
  }

  sym_id= ((symbol*)(stack_head->item->content.ptr))->id;
  toss(env);

  hash_entry= hash(env->symbols, sym_id);
  temp= *hash_entry;
  *hash_entry= (*hash_entry)->next;
  
  if(temp->val!=NULL) {
    free_val(temp->val);
  }
  free(temp->id);
  free(temp);
} 

int main()
{
  environment myenv;
  char in_string[100];

  init_env(&myenv);

  printf("okidok\n ");

  while(fgets(in_string, 100, stdin) != NULL) {
    stack_read(&myenv, in_string);
    printf("okidok\n ");
  }

  exit(EXIT_SUCCESS);
}
1	/* printf */
2	#include <stdio.h>
3	/* EXIT_SUCCESS */
4	#include <stdlib.h>
5	/* NULL */
6	#include <stddef.h>
7	/* dlopen, dlsym, dlerror */
8	#include <dlfcn.h>
9	/* assert */
10	#include <assert.h>
11
12	#define HASHTBLSIZE 65536
13
14	/* First, define some types. */
15
16	/* A value of some type */
17	typedef struct {
18	enum {
19	integer,
20	string,
21	ref, /* Reference (to an element in the
22	hash table) */
23	func, /* Function pointer */
24	symb,
25	list
26	} type; /* Type of stack element */
27
28	union {
29	void ptr; / Pointer to the content */
30	int val; /* ...or an integer */
31	} content; /* Stores a pointer or an integer */
32
33	int refcount; /* Reference counter */
34
35	} value;
36
37	/* A symbol with a name and possible value */
38	/* (These do not need reference counters, they are kept unique by
39	hashing.) */
40	typedef struct symbol_struct {
41	char id; / Symbol name */
42	value val; / The value (if any) bound to it */
43	struct symbol_struct next; / In case of hashing conflicts, a */
44	} symbol; /* symbol is a kind of stack item. */
45
46	/* A type for a hash table for symbols */
47	typedef symbol hashtbl[HASHTBLSIZE]; / Hash table declaration */
48
49	/* An item (value) on a stack */
50	typedef struct stackitem_struct
51	{
52	value item; / The value on the stack */
53	struct stackitem_struct next; / Next item */
54	} stackitem;
55
56	/* An environment; gives access to the stack and a hash table of
57	defined symbols */
58	typedef struct {
59	stackitem head; / Head of the stack */
60	hashtbl symbols; /* Hash table of all variable bindings */
61	int err; /* Error flag */
62	} environment;
63
64	/* A type for pointers to external functions */
65	typedef void (funcp)(environment ); /* funcp is a pointer to a void
66	function (environment ) /
67
68	/* Initialize a newly created environment */
69	void init_env(environment *env)
70	{
71	long i;
72
73	for(i= 0; i<HASHTBLSIZE; i++)
74	env->symbols[i]= NULL;
75	}
76
77	/* Returns a pointer to a pointer to an element in the hash table. */
78	symbol *hash(hashtbl in_hashtbl, const char in_string)
79	{
80	long i= 0;
81	unsigned long out_hash= 0;
82	char key= '\0';
83	symbol **position;
84
85	while(1){ /* Hash in_string */
86	key= in_string[i++];
87	if(key=='\0')
88	break;
89	out_hash= out_hash*32+key;
90	}
91
92	out_hash= out_hash%HASHTBLSIZE;
93	position= &(in_hashtbl[out_hash]);
94
95	while(1){
96	if(position==NULL) / If empty */
97	return position;
98
99	if(strcmp(in_string, (position)->id)==0) / If match */
100	return position;
101
102	position= &((position)->next); / Try next */
103	}
104	}
105
106	/* Generic push function. */
107	int push(stackitem** stack_head, stackitem* in_item)
108	{
109	in_item->next= *stack_head;
110	*stack_head= in_item;
111	return 1;
112	}
113
114	/* Push a value onto the stack */
115	void push_val(stackitem *stack_head, value val)
116	{
117	stackitem *new_item= malloc(sizeof(stackitem));
118	new_item->item= val;
119	val->refcount++;
120	push(stack_head, new_item);
121	}
122
123	/* Push an integer onto the stack. */
124	int push_int(stackitem **stack_head, int in_val)
125	{
126	value *new_value= malloc(sizeof(value));
127	stackitem *new_item= malloc(sizeof(stackitem));
128	new_item->item= new_value;
129
130	new_value->content.val= in_val;
131	new_value->type= integer;
132	new_value->refcount=1;
133
134	push(stack_head, new_item);
135	return 1;
136	}
137
138	/* Copy a string onto the stack. */
139	int push_cstring(stackitem *stack_head, const char in_string)
140	{
141	value *new_value= malloc(sizeof(value));
142	stackitem *new_item= malloc(sizeof(stackitem));
143	new_item->item=new_value;
144
145	new_value->content.ptr= malloc(strlen(in_string)+1);
146	strcpy(new_value->content.ptr, in_string);
147	new_value->type= string;
148	new_value->refcount=1;
149
150	push(stack_head, new_item);
151	return 1;
152	}
153
154	/* Push a symbol onto the stack. */
155	int push_sym(environment env, const char in_string)
156	{
157	stackitem new_item; / The new stack item */
158	/* ...which will contain... */
159	value new_value; / A new symbol value */
160	/* ...which might point to... */
161	symbol *new_symbol; / (if needed) A new actual symbol */
162	/* ...which, if possible, will be bound to... */
163	value new_fvalue; / (if needed) A new function value */
164	/* ...which will point to... */
165	void funcptr; / A function pointer */
166
167	static void handle= NULL; / Dynamic linker handle */
168
169	/* Create a new stack item containing a new value */
170	new_item= malloc(sizeof(stackitem));
171	new_value= malloc(sizeof(value));
172	new_item->item=new_value;
173
174	/* The new value is a symbol */
175	new_value->type= symb;
176	new_value->refcount= 1;
177
178	/* Look up the symbol name in the hash table */
179	new_symbol= hash(env->symbols, in_string);
180	new_value->content.ptr= *new_symbol;
181
182	if(new_symbol==NULL) { / If symbol was undefined */
183
184	/* Create a new symbol */
185	(*new_symbol)= malloc(sizeof(symbol));
186	(new_symbol)->val= NULL; / undefined value */
187	(*new_symbol)->next= NULL;
188	(*new_symbol)->id= malloc(strlen(in_string)+1);
189	strcpy((*new_symbol)->id, in_string);
190
191	/* Intern the new symbol in the hash table */
192	new_value->content.ptr= *new_symbol;
193
194	/* Try to load the symbol name as an external function, to see if
195	we should bind the symbol to a new function pointer value */
196	if(handle==NULL) /* If no handle */
197	handle= dlopen(NULL, RTLD_LAZY);
198
199	funcptr= dlsym(handle, in_string); /* Get function pointer */
200	if(dlerror()==NULL) { /* If a function was found */
201	new_fvalue= malloc(sizeof(value)); /* Create a new value */
202	new_fvalue->type=func; /* The new value is a function pointer */
203	new_fvalue->content.ptr=funcptr; /* Store function pointer */
204	(new_symbol)->val= new_fvalue; / Bind the symbol to the new
205	function value */
206	new_fvalue->refcount= 1;
207	}
208	}
209	push(&(env->head), new_item);
210	return 1;
211	}
212
213	void printerr(const char* in_string) {
214	fprintf(stderr, "Err: %s\n", in_string);
215	}
216
217	/* Throw away a value */
218	void free_val(value *val){
219	stackitem item, temp;
220
221	val->refcount--; /* Decrease the reference count */
222	if(val->refcount == 0){
223	switch (val->type){ /* and free the contents if necessary */
224	case string:
225	free(val->content.ptr);
226	case list: /* lists needs to be freed recursively */
227	item=val->content.ptr;
228	while(item != NULL) { /* for all stack items */
229	free_val(item->item); /* free the value */
230	temp=item->next; /* save next ptr */
231	free(item); /* free the stackitem */
232	item=temp; /* go to next stackitem */
233	}
234	free(val); /* Free the actual list value */
235	break;
236	default:
237	break;
238	}
239	}
240	}
241
242	/* Discard the top element of the stack. */
243	extern void toss(environment *env)
244	{
245	stackitem *temp= env->head;
246
247	if((env->head)==NULL) {
248	printerr("Stack empty");
249	return;
250	}
251
252	free_val(env->head->item); /* Free the value */
253	env->head= env->head->next; /* Remove the top stack item */
254	free(temp); /* Free the old top stack item */
255	}
256
257	/* Print newline. */
258	extern void nl()
259	{
260	printf("\n");
261	}
262
263	/* Prints the top element of the stack. */
264	void print_h(stackitem *stack_head)
265	{
266
267	if(stack_head==NULL) {
268	printerr("Stack empty");
269	return;
270	}
271
272	switch(stack_head->item->type) {
273	case integer:
274	printf("%d", stack_head->item->content.val);
275	break;
276	case string:
277	printf("\"%s\"", (char*)stack_head->item->content.ptr);
278	break;
279	case symb:
280	printf("'%s'", ((symbol *)(stack_head->item->content.ptr))->id);
281	break;
282	default:
283	printf("%p", (funcp)(stack_head->item->content.ptr));
284	break;
285	}
286	}
287
288	extern void print_(environment *env) {
289	print_h(env->head);
290	}
291
292	/* Prints the top element of the stack and then discards it. */
293	extern void print(environment *env)
294	{
295	print_(env);
296	toss(env);
297	}
298
299	/* Only to be called by function printstack. */
300	void print_st(stackitem *stack_head, long counter)
301	{
302	if(stack_head->next != NULL)
303	print_st(stack_head->next, counter+1);
304	printf("%ld: ", counter);
305	print_h(stack_head);
306	nl();
307	}
308
309
310
311	/* Prints the stack. */
312	extern void printstack(environment *env)
313	{
314	if(env->head != NULL) {
315	print_st(env->head, 1);
316	nl();
317	} else {
318	printerr("Stack empty");
319	}
320	}
321
322	/* Swap the two top elements on the stack. */
323	extern void swap(environment *env)
324	{
325	stackitem *temp= env->head;
326
327	if((env->head)==NULL) {
328	printerr("Stack empty");
329	return;
330	}
331
332	if(env->head->next==NULL) {
333	printerr("Not enough arguments");
334	return;
335	}
336
337	env->head= env->head->next;
338	temp->next= env->head->next;
339	env->head->next= temp;
340	}
341
342	stackitem* copy(stackitem* in_item)
343	{
344	stackitem *out_item= malloc(sizeof(stackitem));
345
346	memcpy(out_item, in_item, sizeof(stackitem));
347	out_item->next= NULL;
348
349	return out_item;
350	}
351
352	/* Recall a value from a symbol, if bound */
353	extern void rcl(environment *env)
354	{
355	value *val;
356
357	if(env->head == NULL) {
358	printerr("Stack empty");
359	return;
360	}
361
362	if(env->head->item->type!=symb) {
363	printerr("Not a symbol");
364	return;
365	}
366	val=((symbol *)(env->head->item->content.ptr))->val;
367	if(val == NULL){
368	printerr("Unbound variable");
369	return;
370	}
371	toss(env); /* toss the symbol */
372	push_val(&(env->head), val); /* Return its bound value */
373	}
374
375	/* If the top element is a symbol, determine if it's bound to a
376	function value, and if it is, toss the symbol and execute the
377	function. */
378	extern void eval(environment *env)
379	{
380	funcp in_func;
381	value* val;
382	if(env->head==NULL) {
383	printerr("Stack empty");
384	return;
385	}
386
387	/* if it's a symbol */
388	if(env->head->item->type==symb) {
389
390	/* If it's not bound to anything */
391	if (((symbol *)(env->head->item->content.ptr))->val == NULL) {
392	printerr("Unbound variable");
393	return;
394	}
395
396	/* If it contains a function */
397	if (((symbol *)(env->head->item->content.ptr))->val->type == func) {
398	in_func=
399	(funcp)(((symbol *)(env->head->item->content.ptr))->val->content.ptr);
400	toss(env);
401	(in_func)(env); / Run the function */
402	return;
403	} else { /* If it's not a function */
404	val=((symbol *)(env->head->item->content.ptr))->val;
405	toss(env); /* toss the symbol */
406	push_val(&(env->head), val); /* Return its bound value */
407	}
408	}
409
410	/* If it's a lone function value, run it */
411	if(env->head->item->type==func) {
412	in_func= (funcp)(env->head->item->content.ptr);
413	toss(env);
414	(*in_func)(env);
415	return;
416	}
417
418	}
419
420	/* Make a list. */
421	extern void pack(environment *env)
422	{
423	void* delimiter;
424	stackitem iterator, temp;
425	value *pack;
426
427	delimiter= env->head->item->content.ptr; /* Get delimiter */
428	toss(env);
429
430	iterator= env->head;
431
432	if(iterator==NULL \|\| iterator->item->content.ptr==delimiter) {
433	temp= NULL;
434	toss(env);
435	} else {
436	/* Search for first delimiter */
437	while(iterator->next!=NULL
438	&& iterator->next->item->content.ptr!=delimiter)
439	iterator= iterator->next;
440
441	/* Extract list */
442	temp= env->head;
443	env->head= iterator->next;
444	iterator->next= NULL;
445
446	if(env->head!=NULL)
447	toss(env);
448	}
449
450	/* Push list */
451	pack= malloc(sizeof(value));
452	pack->type= list;
453	pack->content.ptr= temp;
454	pack->refcount= 1;
455
456	temp= malloc(sizeof(stackitem));
457	temp->item= pack;
458
459	push(&(env->head), temp);
460	}
461
462	/* Parse input. */
463	int stack_read(environment env, char in_line)
464	{
465	char temp, rest;
466	int itemp;
467	size_t inlength= strlen(in_line)+1;
468	int convert= 0;
469	static int non_eval_flag= 0;
470
471	temp= malloc(inlength);
472	rest= malloc(inlength);
473
474	do {
475	/* If string */
476	if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
477	push_cstring(&(env->head), temp);
478	break;
479	}
480	/* If integer */
481	if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
482	push_int(&(env->head), itemp);
483	break;
484	}
485	/* Escape ';' with '\' */
486	if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
487	temp[1]= '\0';
488	push_sym(env, temp);
489	break;
490	}
491	/* If symbol */
492	if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
493	push_sym(env, temp);
494	break;
495	}
496	/* If single char */
497	if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
498	if(*temp==';') {
499	if(!non_eval_flag) {
500	eval(env); /* Evaluate top element */
501	break;
502	}
503
504	push_sym(env, ";");
505	break;
506	}
507
508	if(*temp==']') {
509	push_sym(env, "[");
510	pack(env);
511	if(non_eval_flag!=0)
512	non_eval_flag--;
513	break;
514	}
515
516	if(*temp=='[') {
517	push_sym(env, "[");
518	non_eval_flag++;
519	break;
520	}
521	}
522	} while(0);
523
524
525	free(temp);
526
527	if(convert<2) {
528	free(rest);
529	return 0;
530	}
531
532	stack_read(env, rest);
533
534	free(rest);
535	return 1;
536	}
537
538	/* Relocate elements of the list on the stack. */
539	extern void expand(environment *env)
540	{
541	stackitem temp, new_head;
542
543	/* Is top element a list? */
544	if(env->head==NULL \|\| env->head->item->type!=list) {
545	printerr("Stack empty or not a list");
546	return;
547	}
548
549	/* The first list element is the new stack head */
550	new_head= temp= env->head->item->content.ptr;
551
552	env->head->item->refcount++;
553	toss(env);
554
555	/* Find the end of the list */
556	while(temp->next!=NULL)
557	temp= temp->next;
558
559	/* Connect the tail of the list with the old stack head */
560	temp->next= env->head;
561	env->head= new_head; /* ...and voila! */
562
563	}
564
565	/* Compares two elements by reference. */
566	extern void eq(environment *env)
567	{
568	void left, right;
569	int result;
570
571	if((env->head)==NULL \|\| env->head->next==NULL) {
572	printerr("Not enough elements to compare");
573	return;
574	}
575
576	left= env->head->item->content.ptr;
577	swap(env);
578	right= env->head->item->content.ptr;
579	result= (left==right);
580
581	toss(env); toss(env);
582	push_int(&(env->head), result);
583	}
584
585	/* Negates the top element on the stack. */
586	extern void not(environment *env)
587	{
588	int val;
589
590	if((env->head)==NULL \|\| env->head->item->type!=integer) {
591	printerr("Stack empty or element is not a integer");
592	return;
593	}
594
595	val= env->head->item->content.val;
596	toss(env);
597	push_int(&(env->head), !val);
598	}
599
600	/* Compares the two top elements on the stack and return 0 if they're the
601	same. */
602	extern void neq(environment *env)
603	{
604	eq(env);
605	not(env);
606	}
607
608	/* Give a symbol some content. */
609	extern void def(environment *env)
610	{
611	symbol *sym;
612
613	/* Needs two values on the stack, the top one must be a symbol */
614	if(env->head==NULL \|\| env->head->next==NULL
615	\|\| env->head->item->type!=symb) {
616	printerr("Define what?");
617	return;
618	}
619
620	/* long names are a pain */
621	sym=env->head->item->content.ptr;
622
623	/* if the symbol was bound to something else, throw it away */
624	if(sym->val != NULL)
625	free_val(sym->val);
626
627	/* Bind the symbol to the value */
628	sym->val= env->head->next->item;
629	sym->val->refcount++; /* Increase the reference counter */
630
631	toss(env); toss(env);
632	}
633
634	/* Quit stack. */
635	extern void quit(environment *env)
636	{
637	exit(EXIT_SUCCESS);
638	}
639
640	/* Clear stack */
641	extern void clear(environment *env)
642	{
643	while(env->head!=NULL)
644	toss(env);
645	}
646
647	/* List all defined words */
648	extern void words(environment *env)
649	{
650	symbol *temp;
651	int i;
652
653	for(i= 0; i<HASHTBLSIZE; i++) {
654	temp= env->symbols[i];
655	while(temp!=NULL) {
656	printf("%s\n", temp->id);
657	temp= temp->next;
658	}
659	}
660	}
661
662	/* Forgets a symbol (remove it from the hash table) */
663	extern void forget(environment *env)
664	{
665	char* sym_id;
666	stackitem *stack_head= env->head;
667	symbol *hash_entry, temp;
668
669	if(stack_head==NULL \|\| stack_head->item->type!=symb) {
670	printerr("Stack empty or not a symbol");
671	return;
672	}
673
674	sym_id= ((symbol*)(stack_head->item->content.ptr))->id;
675	toss(env);
676
677	hash_entry= hash(env->symbols, sym_id);
678	temp= *hash_entry;
679	hash_entry= (hash_entry)->next;
680
681	if(temp->val!=NULL) {
682	free_val(temp->val);
683	}
684	free(temp->id);
685	free(temp);
686	}
687
688	int main()
689	{
690	environment myenv;
691	char in_string[100];
692
693	init_env(&myenv);
694
695	printf("okidok\n ");
696
697	while(fgets(in_string, 100, stdin) != NULL) {
698	stack_read(&myenv, in_string);
699	printf("okidok\n ");
700	}
701
702	exit(EXIT_SUCCESS);
703	}