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); /* The new reference 
                                                         shouldn't point at 
                                                         NULL */
    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. */
extern void print_(stackitem** stack_head)
{
  stackitem* temp= *stack_head;

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

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

  switch(temp->type) {
  case value:
    printf("%d", temp->content.val);
    break;
  case string:
    printf("\"%s\"", (char*)temp->content.ptr);
    break;
  case symbol:
    printf("%s", temp->id);
    break;
  default:
    printf("%p", temp->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); / The new reference
164	shouldn't point at
165	NULL */
166	new_item->type= ref;
167	}
168
169	push(stack_head, new_item);
170	return 1;
171	}
172
173	void printerr(const char* in_string) {
174	fprintf(stderr, "Err: %s\n", in_string);
175	}
176
177	/* Discard the top element of the stack. */
178	extern void toss(stackitem** stack_head)
179	{
180	stackitem* temp= *stack_head;
181
182	if((*stack_head)==NULL) {
183	printerr("Stack empty");
184	return;
185	}
186
187	if((*stack_head)->type==string)
188	free((*stack_head)->content.ptr);
189
190	stack_head= (stack_head)->next;
191	free(temp);
192	}
193
194	/* Print newline. */
195	extern void nl()
196	{
197	printf("\n");
198	}
199
200	/* Prints the top element of the stack. */
201	extern void print_(stackitem** stack_head)
202	{
203	stackitem* temp= *stack_head;
204
205	if(temp==NULL) {
206	printerr("Stack empty");
207	return;
208	}
209
210	while(temp->type==ref)
211	temp= temp->content.ptr;
212
213	switch(temp->type) {
214	case value:
215	printf("%d", temp->content.val);
216	break;
217	case string:
218	printf("\"%s\"", (char*)temp->content.ptr);
219	break;
220	case symbol:
221	printf("%s", temp->id);
222	break;
223	default:
224	printf("%p", temp->content.ptr);
225	break;
226	}
227	}
228
229	/* Prints the top element of the stack and then discards it. */
230	extern void print(stackitem** stack_head)
231	{
232	print_(stack_head);
233	toss(stack_head);
234	}
235
236	/* Only to be called by function printstack. */
237	void print_st(stackitem* stack_head, long counter)
238	{
239	if(stack_head->next != NULL)
240	print_st(stack_head->next, counter+1);
241
242	printf("%ld: ", counter);
243	print_(&stack_head);
244	nl();
245	}
246
247	/* Prints the stack. */
248	extern void printstack(stackitem** stack_head)
249	{
250	if(*stack_head != NULL) {
251	print_st(*stack_head, 1);
252	nl();
253	} else {
254	printerr("Stack empty");
255	}
256	}
257
258	/* If the top element is a reference, determine if it's a reference to a
259	function, and if it is, toss the reference and execute the function. */
260	extern void eval(stackitem** stack_head)
261	{
262	funcp in_func;
263	stackitem* temp= *stack_head;
264
265	if(temp==NULL) {
266	printerr("Stack empty");
267	return;
268	}
269
270	while(temp->type==ref)
271	temp= temp->content.ptr;
272
273	if(temp->type==func) {
274	in_func= (funcp)(temp->content.ptr);
275	toss(stack_head);
276	(*in_func)(stack_head);
277	return;
278	}
279
280	printerr("Couldn't evaluate");
281	}
282
283	/* Make a list. */
284	extern void pack(stackitem** stack_head)
285	{
286	void* delimiter;
287	stackitem iterator, temp, *pack;
288
289	if((*stack_head)==NULL) {
290	printerr("Stack empty");
291	return;
292	}
293
294	delimiter= (stack_head)->content.ptr; / Get delimiter */
295	toss(stack_head);
296
297	iterator= *stack_head;
298
299	/* Search for first delimiter */
300	while(iterator->next!=NULL && iterator->next->content.ptr!=delimiter)
301	iterator= iterator->next;
302
303	/* Extract list */
304	temp= *stack_head;
305	*stack_head= iterator->next;
306	iterator->next= NULL;
307
308	if(stack_head!=NULL && (stack_head)->content.ptr==delimiter)
309	toss(stack_head);
310
311	/* Push list */
312	pack= malloc(sizeof(stackitem));
313	pack->type= list;
314	pack->content.ptr= temp;
315
316	push(stack_head, pack);
317	}
318
319	/* Parse input. */
320	int stack_read(stackitem** stack_head, hashtbl in_hash, char* in_line)
321	{
322	char temp, rest;
323	int itemp;
324	size_t inlength= strlen(in_line)+1;
325	int convert= 0;
326	static int non_eval_flag= 0;
327
328	temp= malloc(inlength);
329	rest= malloc(inlength);
330
331	do {
332	/* If string */
333	if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
334	push_cstring(stack_head, temp);
335	break;
336	}
337	/* If value */
338	if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
339	push_val(stack_head, itemp);
340	break;
341	}
342	/* Escape ';' with '\' */
343	if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
344	temp[1]= '\0';
345	push_ref(stack_head, in_hash, temp);
346	break;
347	}
348	/* If symbol */
349	if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
350	push_ref(stack_head, in_hash, temp);
351	break;
352	}
353	/* If single char */
354	if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
355	if(*temp==';') {
356	if(!non_eval_flag) {
357	eval(stack_head); /* Evaluate top element */
358	break;
359	}
360
361	push_ref(stack_head, in_hash, ";");
362	break;
363	}
364
365	if(*temp==']') {
366	push_ref(stack_head, in_hash, "[");
367	pack(stack_head);
368	if(non_eval_flag!=0)
369	non_eval_flag--;
370	break;
371	}
372
373	if(*temp=='[') {
374	push_ref(stack_head, in_hash, "[");
375	non_eval_flag++;
376	break;
377	}
378	}
379	} while(0);
380
381
382	free(temp);
383
384	if(convert<2) {
385	free(rest);
386	return 0;
387	}
388
389	stack_read(stack_head, in_hash, rest);
390
391	free(rest);
392	return 1;
393	}
394
395	/* Relocate elements of the list on the stack. */
396	extern void expand(stackitem** stack_head)
397	{
398	stackitem temp, new_head;
399
400	/* Is top element a list? */
401	if((stack_head)==NULL \|\| (stack_head)->type!=list) {
402	printerr("Stack empty or not a list");
403	return;
404	}
405
406	/* The first list element is the new stack head */
407	new_head= temp= (*stack_head)->content.ptr;
408	toss(stack_head);
409
410	/* Search the end of the list */
411	while(temp->next!=NULL)
412	temp= temp->next;
413
414	/* Connect the the tail of the list with the old stack head */
415	temp->next= *stack_head;
416	stack_head= new_head; / ...and voila! */
417	}
418
419	/* Swap the two top elements on the stack. */
420	extern void swap(stackitem** stack_head)
421	{
422	stackitem* temp= (*stack_head);
423
424	if((*stack_head)==NULL) {
425	printerr("Stack empty");
426	return;
427	}
428
429	if((*stack_head)->next==NULL)
430	return;
431
432	stack_head= (stack_head)->next;
433	temp->next= (*stack_head)->next;
434	(*stack_head)->next= temp;
435	}
436
437	/* Compares two elements by reference. */
438	extern void eq(stackitem** stack_head)
439	{
440	void left, right;
441	int result;
442
443	if((stack_head)==NULL \|\| (stack_head)->next==NULL) {
444	printerr("Not enough elements to compare");
445	return;
446	}
447
448	left= (*stack_head)->content.ptr;
449	swap(stack_head);
450	right= (*stack_head)->content.ptr;
451	result= (left==right);
452
453	toss(stack_head); toss(stack_head);
454	push_val(stack_head, (left==right));
455	}
456
457	/* Negates the top element on the stack. */
458	extern void not(stackitem** stack_head)
459	{
460	int value;
461
462	if((stack_head)==NULL \|\| (stack_head)->type!=value) {
463	printerr("Stack empty or element is not a value");
464	return;
465	}
466
467	value= (*stack_head)->content.val;
468	toss(stack_head);
469	push_val(stack_head, !value);
470	}
471
472	/* Compares the two top elements on the stack and return 0 if they're the
473	same. */
474	extern void neq(stackitem** stack_head)
475	{
476	eq(stack_head);
477	not(stack_head);
478	}
479
480	/* Give a symbol some content. */
481	extern void def(stackitem** stack_head)
482	{
483	stackitem temp, value;
484
485	if(stack_head==NULL \|\| (stack_head)->next==NULL
486	\|\| (*stack_head)->type!=ref) {
487	printerr("Define what?");
488	return;
489	}
490
491	temp= (*stack_head)->content.ptr;
492	value= (*stack_head)->next;
493	temp->content= value->content;
494	value->content.ptr=NULL;
495	temp->type= value->type;
496
497	toss(stack_head); toss(stack_head);
498	}
499
500	/* Quit stack. */
501	extern void quit()
502	{
503	exit(EXIT_SUCCESS);
504	}
505
506	int main()
507	{
508	stackitem* s= NULL;
509	hashtbl myhash;
510	char in_string[100];
511
512	init_hashtbl(myhash);
513
514	printf("okidok\n ");
515
516	while(fgets(in_string, 100, stdin) != NULL) {
517	stack_read(&s, myhash, in_string);
518	printf("okidok\n ");
519	}
520
521	exit(EXIT_SUCCESS);
522	}
523
524	/* Local Variables: */
525	/* compile-command:"make CFLAGS=\"-Wall -g -rdynamic -ldl\" stack" */
526	/* End: */