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

typedef struct stack_item
{
  enum {
    value,                      /* Integer */
    string,
    ref,                        /* Reference (to an element in the
                                   hash table) */
    func,                       /* Function pointer */
    symbol, 
    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 */

  char* id;                     /* Symbol name */
  struct stack_item* next;      /* Next element */
} stackitem;


typedef stackitem* hashtbl[HASHTBLSIZE]; /* Hash table declaration */
typedef void (*funcp)(stackitem**); /* funcp is a pointer to a
                                       void function (stackitem **) */

/* Initialize a newly created hash table. */
void init_hashtbl(hashtbl out_hash)
{
  long i;

  for(i= 0; i<HASHTBLSIZE; i++)
    out_hash[i]= NULL;
}

/* Returns a pointer to an element in the hash table. */
stackitem** hash(hashtbl in_hashtbl, const char* in_string)
{
  long i= 0;
  unsigned long out_hash= 0;
  char key= '\0';
  stackitem** 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(position != NULL){
    if(*position==NULL)         /* If empty */
      return position;
    
    if(strcmp(in_string, (*position)->id)==0) /* If match */
      return position;

    position= &((*position)->next); /* Try next */
  }
  return NULL;                  /* end of list reached without finding
                                   an empty position */
}

/* 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 on the stack. */
int push_val(stackitem** stack_head, int in_val) 
{
  stackitem* new_item= malloc(sizeof(stackitem));
  assert(new_item != NULL);
  new_item->content.val= in_val;
  new_item->type= value;

  push(stack_head, new_item);
  return 1;
}

/* Copy a string onto the stack. */
int push_cstring(stackitem** stack_head, const char* in_string)
{
  stackitem* new_item= malloc(sizeof(stackitem));
  new_item->content.ptr= malloc(strlen(in_string)+1);
  strcpy(new_item->content.ptr, in_string);
  new_item->type= string;

  push(stack_head, new_item);
  return 1;
}

/* Create a new hash entry. */
int mk_hashentry(hashtbl in_hashtbl, stackitem* in_item, const char* id)
{
  in_item->id= malloc(strlen(id)+1);

  strcpy(in_item->id, id);
  push(hash(in_hashtbl, id), in_item);

  return 1;
}

/* Define a new function in the hash table. */
void def_func(hashtbl in_hashtbl, funcp in_func, const char* id)
{
  stackitem* temp= malloc(sizeof(stackitem));

  temp->type= func;
  temp->content.ptr= in_func;

  mk_hashentry(in_hashtbl, temp, id);
}

/* Define a new symbol in the hash table. */
void def_sym(hashtbl in_hashtbl, const char* id)
{
  stackitem* temp= malloc(sizeof(stackitem));
  
  temp->type= symbol;
  mk_hashentry(in_hashtbl, temp, id);
}

/* Push a reference to an entry in the hash table onto the stack. */
int push_ref(stackitem** stack_head, hashtbl in_hash, const char* in_string)
{
  static void* handle= NULL;
  void* symbol;

  stackitem* new_item= malloc(sizeof(stackitem));
  new_item->content.ptr= *hash(in_hash, in_string);
  new_item->type= ref;

  if(new_item->content.ptr==NULL) { /* If hash entry empty */
    if(handle==NULL)            /* If no handle */
      handle= dlopen(NULL, RTLD_LAZY);    

    symbol= dlsym(handle, in_string); /* Get function pointer */
    if(dlerror()==NULL)         /* If existing function pointer */
      def_func(in_hash, symbol, in_string); /* Store function pointer */
    else
      def_sym(in_hash, in_string); /* Make symbol */
      
    new_item->content.ptr= *hash(in_hash, in_string); /* XXX */
    new_item->type= ref;
  }

  push(stack_head, new_item);
  return 1;
}

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

/* Discard the top element of the stack. */
extern void toss(stackitem** stack_head)
{
  stackitem* temp= *stack_head;

  if((*stack_head)==NULL) {
    printerr("Stack empty");
    return;
  }
  
  if((*stack_head)->type==string)
    free((*stack_head)->content.ptr);

  *stack_head= (*stack_head)->next;
  free(temp);
}

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

/* Prints the top element of the stack. */
void print_(stackitem** stack_head)
{
  if((*stack_head)==NULL) {
    printerr("Stack empty");
    return;
  }

  switch((*stack_head)->type) {
  case value:
    printf("%d", (*stack_head)->content.val);
    break;
  case string:
    printf("\"%s\"", (char*)(*stack_head)->content.ptr);
    break;
  case ref:
    printf("%s", ((stackitem*)(*stack_head)->content.ptr)->id);
    break;
  case symbol:
  default:
    printf("%p", (*stack_head)->content.ptr);
    break;
  }
}

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

/* 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_(&stack_head);
  nl();
}

/* Prints the stack. */
extern void printstack(stackitem** stack_head)
{
  if(*stack_head != NULL) {
    print_st(*stack_head, 1);
    nl();
  } else {
    printerr("Stack empty");
  }
}

/* If the top element is a reference, determine if it's a reference to a
   function, and if it is, toss the reference and execute the function. */
extern void eval(stackitem** stack_head)
{
  funcp in_func;
  stackitem* temp= *stack_head;

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

  while(temp->type==ref)
    temp= temp->content.ptr;

  if(temp->type==func) {
    in_func= (funcp)(temp->content.ptr);
    toss(stack_head); 
    (*in_func)(stack_head);
    return;
  } 
    
  printerr("Couldn't evaluate");
}

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

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

  delimiter= (*stack_head)->content.ptr; /* Get delimiter */
  toss(stack_head);

  iterator= *stack_head;

  /* Search for first delimiter */
  while(iterator->next!=NULL && iterator->next->content.ptr!=delimiter)
    iterator= iterator->next;

  /* Extract list */
  temp= *stack_head;
  *stack_head= iterator->next;
  iterator->next= NULL;
  
  if(*stack_head!=NULL && (*stack_head)->content.ptr==delimiter)
    toss(stack_head);

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

  push(stack_head, pack);
}

/* Parse input. */
int stack_read(stackitem** stack_head, hashtbl in_hash, 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(stack_head, temp);
      break;
    }
    /* If value */
    if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
      push_val(stack_head, itemp);
      break;
    }
    /* Escape ';' with '\' */
    if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
      temp[1]= '\0'; 
      push_ref(stack_head, in_hash, temp);
      break;
    } 
    /* If symbol */
    if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
        push_ref(stack_head, in_hash, temp);
        break;
    }
    /* If single char */
    if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
      if(*temp==';') {
        if(!non_eval_flag) {
          eval(stack_head);             /* Evaluate top element */
          break;
        }
        
        push_ref(stack_head, in_hash, ";");
        break;
      }

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

      if(*temp=='[') {
        push_ref(stack_head, in_hash, "[");
        non_eval_flag++;
        break;
      }
    }
  } while(0);


  free(temp);

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

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

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

  /* The first list element is the new stack head */
  new_head= temp= (*stack_head)->content.ptr;
  toss(stack_head);

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

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

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

  if((*stack_head)->next==NULL)
    return;

  *stack_head= (*stack_head)->next;
  temp->next= (*stack_head)->next;
  (*stack_head)->next= temp;
} 

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

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

  left= (*stack_head)->content.ptr;
  swap(stack_head);
  right= (*stack_head)->content.ptr;
  result= (left==right);
  
  toss(stack_head); toss(stack_head);
  push_val(stack_head, (left==right));
}

/* Negates the top element on the stack. */
extern void not(stackitem** stack_head)
{
  int value;

  if((*stack_head)==NULL || (*stack_head)->type!=value) {
    printerr("Stack empty or element is not a value");
    return;
  }

  value= (*stack_head)->content.val;
  toss(stack_head);
  push_val(stack_head, !value);
}

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

/* Give a symbol some content. */
extern void def(stackitem** stack_head)
{
  stackitem *temp, *value;

  if(*stack_head==NULL || (*stack_head)->next==NULL 
     || (*stack_head)->type!=ref) {
    printerr("Define what?");
    return;
  }

  temp= (*stack_head)->content.ptr;
  value= (*stack_head)->next;
  temp->content= value->content;
  value->content.ptr=NULL;
  temp->type= value->type;

  toss(stack_head); toss(stack_head);
} 

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

int main()
{
  stackitem* s= NULL;
  hashtbl myhash;
  char in_string[100];

  init_hashtbl(myhash);

  printf("okidok\n ");

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

  exit(EXIT_SUCCESS);
}

/* Local Variables: */
/* compile-command:"make CFLAGS=\"-Wall -g -rdynamic -ldl\" stack" */
/* End: */
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	typedef struct stack_item
15	{
16	enum {
17	value, /* Integer */
18	string,
19	ref, /* Reference (to an element in the
20	hash table) */
21	func, /* Function pointer */
22	symbol,
23	list
24	} type; /* Type of stack element */
25
26	union {
27	void* ptr; /* Pointer to the content */
28	int val; /* ...or an integer */
29	} content; /* Stores a pointer or an integer */
30
31	char* id; /* Symbol name */
32	struct stack_item* next; /* Next element */
33	} stackitem;
34
35
36	typedef stackitem* hashtbl[HASHTBLSIZE]; /* Hash table declaration */
37	typedef void (funcp)(stackitem); / funcp is a pointer to a
38	void function (stackitem *) /
39
40	/* Initialize a newly created hash table. */
41	void init_hashtbl(hashtbl out_hash)
42	{
43	long i;
44
45	for(i= 0; i<HASHTBLSIZE; i++)
46	out_hash[i]= NULL;
47	}
48
49	/* Returns a pointer to an element in the hash table. */
50	stackitem** hash(hashtbl in_hashtbl, const char* in_string)
51	{
52	long i= 0;
53	unsigned long out_hash= 0;
54	char key= '\0';
55	stackitem** position;
56
57	while(1){ /* Hash in_string */
58	key= in_string[i++];
59	if(key=='\0')
60	break;
61	out_hash= out_hash*32+key;
62	}
63
64	out_hash= out_hash%HASHTBLSIZE;
65	position= &(in_hashtbl[out_hash]);
66
67	while(position != NULL){
68	if(position==NULL) / If empty */
69	return position;
70
71	if(strcmp(in_string, (position)->id)==0) / If match */
72	return position;
73
74	position= &((position)->next); / Try next */
75	}
76	return NULL; /* end of list reached without finding
77	an empty position */
78	}
79
80	/* Generic push function. */
81	int push(stackitem** stack_head, stackitem* in_item)
82	{
83	in_item->next= *stack_head;
84	*stack_head= in_item;
85	return 1;
86	}
87
88	/* Push a value on the stack. */
89	int push_val(stackitem** stack_head, int in_val)
90	{
91	stackitem* new_item= malloc(sizeof(stackitem));
92	assert(new_item != NULL);
93	new_item->content.val= in_val;
94	new_item->type= value;
95
96	push(stack_head, new_item);
97	return 1;
98	}
99
100	/* Copy a string onto the stack. */
101	int push_cstring(stackitem** stack_head, const char* in_string)
102	{
103	stackitem* new_item= malloc(sizeof(stackitem));
104	new_item->content.ptr= malloc(strlen(in_string)+1);
105	strcpy(new_item->content.ptr, in_string);
106	new_item->type= string;
107
108	push(stack_head, new_item);
109	return 1;
110	}
111
112	/* Create a new hash entry. */
113	int mk_hashentry(hashtbl in_hashtbl, stackitem* in_item, const char* id)
114	{
115	in_item->id= malloc(strlen(id)+1);
116
117	strcpy(in_item->id, id);
118	push(hash(in_hashtbl, id), in_item);
119
120	return 1;
121	}
122
123	/* Define a new function in the hash table. */
124	void def_func(hashtbl in_hashtbl, funcp in_func, const char* id)
125	{
126	stackitem* temp= malloc(sizeof(stackitem));
127
128	temp->type= func;
129	temp->content.ptr= in_func;
130
131	mk_hashentry(in_hashtbl, temp, id);
132	}
133
134	/* Define a new symbol in the hash table. */
135	void def_sym(hashtbl in_hashtbl, const char* id)
136	{
137	stackitem* temp= malloc(sizeof(stackitem));
138
139	temp->type= symbol;
140	mk_hashentry(in_hashtbl, temp, id);
141	}
142
143	/* Push a reference to an entry in the hash table onto the stack. */
144	int push_ref(stackitem** stack_head, hashtbl in_hash, const char* in_string)
145	{
146	static void* handle= NULL;
147	void* symbol;
148
149	stackitem* new_item= malloc(sizeof(stackitem));
150	new_item->content.ptr= *hash(in_hash, in_string);
151	new_item->type= ref;
152
153	if(new_item->content.ptr==NULL) { /* If hash entry empty */
154	if(handle==NULL) /* If no handle */
155	handle= dlopen(NULL, RTLD_LAZY);
156
157	symbol= dlsym(handle, in_string); /* Get function pointer */
158	if(dlerror()==NULL) /* If existing function pointer */
159	def_func(in_hash, symbol, in_string); /* Store function pointer */
160	else
161	def_sym(in_hash, in_string); /* Make symbol */
162
163	new_item->content.ptr= hash(in_hash, in_string); / XXX */
164	new_item->type= ref;
165	}
166
167	push(stack_head, new_item);
168	return 1;
169	}
170
171	void printerr(const char* in_string) {
172	fprintf(stderr, "Err: %s\n", in_string);
173	}
174
175	/* Discard the top element of the stack. */
176	extern void toss(stackitem** stack_head)
177	{
178	stackitem* temp= *stack_head;
179
180	if((*stack_head)==NULL) {
181	printerr("Stack empty");
182	return;
183	}
184
185	if((*stack_head)->type==string)
186	free((*stack_head)->content.ptr);
187
188	stack_head= (stack_head)->next;
189	free(temp);
190	}
191
192	/* Print newline. */
193	extern void nl()
194	{
195	printf("\n");
196	}
197
198	/* Prints the top element of the stack. */
199	void print_(stackitem** stack_head)
200	{
201	if((*stack_head)==NULL) {
202	printerr("Stack empty");
203	return;
204	}
205
206	switch((*stack_head)->type) {
207	case value:
208	printf("%d", (*stack_head)->content.val);
209	break;
210	case string:
211	printf("\"%s\"", (char)(stack_head)->content.ptr);
212	break;
213	case ref:
214	printf("%s", ((stackitem)(stack_head)->content.ptr)->id);
215	break;
216	case symbol:
217	default:
218	printf("%p", (*stack_head)->content.ptr);
219	break;
220	}
221	}
222
223	/* Prints the top element of the stack and then discards it. */
224	extern void print(stackitem** stack_head)
225	{
226	print_(stack_head);
227	toss(stack_head);
228	}
229
230	/* Only to be called by function printstack. */
231	void print_st(stackitem* stack_head, long counter)
232	{
233	if(stack_head->next != NULL)
234	print_st(stack_head->next, counter+1);
235
236	printf("%ld: ", counter);
237	print_(&stack_head);
238	nl();
239	}
240
241	/* Prints the stack. */
242	extern void printstack(stackitem** stack_head)
243	{
244	if(*stack_head != NULL) {
245	print_st(*stack_head, 1);
246	nl();
247	} else {
248	printerr("Stack empty");
249	}
250	}
251
252	/* If the top element is a reference, determine if it's a reference to a
253	function, and if it is, toss the reference and execute the function. */
254	extern void eval(stackitem** stack_head)
255	{
256	funcp in_func;
257	stackitem* temp= *stack_head;
258
259	if(temp==NULL) {
260	printerr("Stack empty");
261	return;
262	}
263
264	while(temp->type==ref)
265	temp= temp->content.ptr;
266
267	if(temp->type==func) {
268	in_func= (funcp)(temp->content.ptr);
269	toss(stack_head);
270	(*in_func)(stack_head);
271	return;
272	}
273
274	printerr("Couldn't evaluate");
275	}
276
277	/* Make a list. */
278	extern void pack(stackitem** stack_head)
279	{
280	void* delimiter;
281	stackitem iterator, temp, *pack;
282
283	if((*stack_head)==NULL) {
284	printerr("Stack empty");
285	return;
286	}
287
288	delimiter= (stack_head)->content.ptr; / Get delimiter */
289	toss(stack_head);
290
291	iterator= *stack_head;
292
293	/* Search for first delimiter */
294	while(iterator->next!=NULL && iterator->next->content.ptr!=delimiter)
295	iterator= iterator->next;
296
297	/* Extract list */
298	temp= *stack_head;
299	*stack_head= iterator->next;
300	iterator->next= NULL;
301
302	if(stack_head!=NULL && (stack_head)->content.ptr==delimiter)
303	toss(stack_head);
304
305	/* Push list */
306	pack= malloc(sizeof(stackitem));
307	pack->type= list;
308	pack->content.ptr= temp;
309
310	push(stack_head, pack);
311	}
312
313	/* Parse input. */
314	int stack_read(stackitem** stack_head, hashtbl in_hash, char* in_line)
315	{
316	char temp, rest;
317	int itemp;
318	size_t inlength= strlen(in_line)+1;
319	int convert= 0;
320	static int non_eval_flag= 0;
321
322	temp= malloc(inlength);
323	rest= malloc(inlength);
324
325	do {
326	/* If string */
327	if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
328	push_cstring(stack_head, temp);
329	break;
330	}
331	/* If value */
332	if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
333	push_val(stack_head, itemp);
334	break;
335	}
336	/* Escape ';' with '\' */
337	if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
338	temp[1]= '\0';
339	push_ref(stack_head, in_hash, temp);
340	break;
341	}
342	/* If symbol */
343	if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
344	push_ref(stack_head, in_hash, temp);
345	break;
346	}
347	/* If single char */
348	if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
349	if(*temp==';') {
350	if(!non_eval_flag) {
351	eval(stack_head); /* Evaluate top element */
352	break;
353	}
354
355	push_ref(stack_head, in_hash, ";");
356	break;
357	}
358
359	if(*temp==']') {
360	push_ref(stack_head, in_hash, "[");
361	pack(stack_head);
362	if(non_eval_flag!=0)
363	non_eval_flag--;
364	break;
365	}
366
367	if(*temp=='[') {
368	push_ref(stack_head, in_hash, "[");
369	non_eval_flag++;
370	break;
371	}
372	}
373	} while(0);
374
375
376	free(temp);
377
378	if(convert<2) {
379	free(rest);
380	return 0;
381	}
382
383	stack_read(stack_head, in_hash, rest);
384
385	free(rest);
386	return 1;
387	}
388
389	/* Relocate elements of the list on the stack. */
390	extern void expand(stackitem** stack_head)
391	{
392	stackitem temp, new_head;
393
394	/* Is top element a list? */
395	if((stack_head)==NULL \|\| (stack_head)->type!=list) {
396	printerr("Stack empty or not a list");
397	return;
398	}
399
400	/* The first list element is the new stack head */
401	new_head= temp= (*stack_head)->content.ptr;
402	toss(stack_head);
403
404	/* Search the end of the list */
405	while(temp->next!=NULL)
406	temp= temp->next;
407
408	/* Connect the the tail of the list with the old stack head */
409	temp->next= *stack_head;
410	stack_head= new_head; / ...and voila! */
411	}
412
413	/* Swap the two top elements on the stack. */
414	extern void swap(stackitem** stack_head)
415	{
416	stackitem* temp= (*stack_head);
417
418	if((*stack_head)==NULL) {
419	printerr("Stack empty");
420	return;
421	}
422
423	if((*stack_head)->next==NULL)
424	return;
425
426	stack_head= (stack_head)->next;
427	temp->next= (*stack_head)->next;
428	(*stack_head)->next= temp;
429	}
430
431	/* Compares two elements by reference. */
432	extern void eq(stackitem** stack_head)
433	{
434	void left, right;
435	int result;
436
437	if((stack_head)==NULL \|\| (stack_head)->next==NULL) {
438	printerr("Not enough elements to compare");
439	return;
440	}
441
442	left= (*stack_head)->content.ptr;
443	swap(stack_head);
444	right= (*stack_head)->content.ptr;
445	result= (left==right);
446
447	toss(stack_head); toss(stack_head);
448	push_val(stack_head, (left==right));
449	}
450
451	/* Negates the top element on the stack. */
452	extern void not(stackitem** stack_head)
453	{
454	int value;
455
456	if((stack_head)==NULL \|\| (stack_head)->type!=value) {
457	printerr("Stack empty or element is not a value");
458	return;
459	}
460
461	value= (*stack_head)->content.val;
462	toss(stack_head);
463	push_val(stack_head, !value);
464	}
465
466	/* Compares the two top elements on the stack and return 0 if they're the
467	same. */
468	extern void neq(stackitem** stack_head)
469	{
470	eq(stack_head);
471	not(stack_head);
472	}
473
474	/* Give a symbol some content. */
475	extern void def(stackitem** stack_head)
476	{
477	stackitem temp, value;
478
479	if(stack_head==NULL \|\| (stack_head)->next==NULL
480	\|\| (*stack_head)->type!=ref) {
481	printerr("Define what?");
482	return;
483	}
484
485	temp= (*stack_head)->content.ptr;
486	value= (*stack_head)->next;
487	temp->content= value->content;
488	value->content.ptr=NULL;
489	temp->type= value->type;
490
491	toss(stack_head); toss(stack_head);
492	}
493
494	/* Quit stack. */
495	extern void quit()
496	{
497	exit(EXIT_SUCCESS);
498	}
499
500	int main()
501	{
502	stackitem* s= NULL;
503	hashtbl myhash;
504	char in_string[100];
505
506	init_hashtbl(myhash);
507
508	printf("okidok\n ");
509
510	while(fgets(in_string, 100, stdin) != NULL) {
511	stack_read(&s, myhash, in_string);
512	printf("okidok\n ");
513	}
514
515	exit(EXIT_SUCCESS);
516	}
517
518	/* Local Variables: */
519	/* compile-command:"make CFLAGS=\"-Wall -g -rdynamic -ldl\" stack" */
520	/* End: */