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(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 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:
  case func:
    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;

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

  iterator= *stack_head;

  if(iterator==NULL || iterator->content.ptr==delimiter) {
    temp= NULL;
    toss(stack_head);
  } else {
    /* 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);

  if(temp==NULL)
    return;

  /* 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);
}

/* Clear stack */
extern void clear(stackitem** stack_head)
{
  while(*stack_head!=NULL)
    toss(stack_head);
}

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(1){
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	}
77
78	/* Generic push function. */
79	int push(stackitem** stack_head, stackitem* in_item)
80	{
81	in_item->next= *stack_head;
82	*stack_head= in_item;
83	return 1;
84	}
85
86	/* Push a value on the stack. */
87	int push_val(stackitem** stack_head, int in_val)
88	{
89	stackitem* new_item= malloc(sizeof(stackitem));
90	assert(new_item != NULL);
91	new_item->content.val= in_val;
92	new_item->type= value;
93
94	push(stack_head, new_item);
95	return 1;
96	}
97
98	/* Copy a string onto the stack. */
99	int push_cstring(stackitem** stack_head, const char* in_string)
100	{
101	stackitem* new_item= malloc(sizeof(stackitem));
102	new_item->content.ptr= malloc(strlen(in_string)+1);
103	strcpy(new_item->content.ptr, in_string);
104	new_item->type= string;
105
106	push(stack_head, new_item);
107	return 1;
108	}
109
110	/* Create a new hash entry. */
111	int mk_hashentry(hashtbl in_hashtbl, stackitem* in_item, const char* id)
112	{
113	in_item->id= malloc(strlen(id)+1);
114
115	strcpy(in_item->id, id);
116	push(hash(in_hashtbl, id), in_item);
117
118	return 1;
119	}
120
121	/* Define a new function in the hash table. */
122	void def_func(hashtbl in_hashtbl, funcp in_func, const char* id)
123	{
124	stackitem* temp= malloc(sizeof(stackitem));
125
126	temp->type= func;
127	temp->content.ptr= in_func;
128
129	mk_hashentry(in_hashtbl, temp, id);
130	}
131
132	/* Define a new symbol in the hash table. */
133	void def_sym(hashtbl in_hashtbl, const char* id)
134	{
135	stackitem* temp= malloc(sizeof(stackitem));
136
137	temp->type= symbol;
138	mk_hashentry(in_hashtbl, temp, id);
139	}
140
141	/* Push a reference to an entry in the hash table onto the stack. */
142	int push_ref(stackitem** stack_head, hashtbl in_hash, const char* in_string)
143	{
144	static void* handle= NULL;
145	void* symbol;
146
147	stackitem* new_item= malloc(sizeof(stackitem));
148	new_item->content.ptr= *hash(in_hash, in_string);
149	new_item->type= ref;
150
151	if(new_item->content.ptr==NULL) { /* If hash entry empty */
152	if(handle==NULL) /* If no handle */
153	handle= dlopen(NULL, RTLD_LAZY);
154
155	symbol= dlsym(handle, in_string); /* Get function pointer */
156	if(dlerror()==NULL) /* If existing function pointer */
157	def_func(in_hash, symbol, in_string); /* Store function pointer */
158	else
159	def_sym(in_hash, in_string); /* Make symbol */
160
161	new_item->content.ptr= hash(in_hash, in_string); / The new reference
162	shouldn't point at
163	NULL */
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	extern void print_(stackitem** stack_head)
200	{
201	stackitem* temp= *stack_head;
202
203	if(temp==NULL) {
204	printerr("Stack empty");
205	return;
206	}
207
208	while(temp->type==ref)
209	temp= temp->content.ptr;
210
211	switch(temp->type) {
212	case value:
213	printf("%d", temp->content.val);
214	break;
215	case string:
216	printf("\"%s\"", (char*)temp->content.ptr);
217	break;
218	case symbol:
219	case func:
220	printf("%s", temp->id);
221	break;
222	default:
223	printf("%p", temp->content.ptr);
224	break;
225	}
226	}
227
228	/* Prints the top element of the stack and then discards it. */
229	extern void print(stackitem** stack_head)
230	{
231	print_(stack_head);
232	toss(stack_head);
233	}
234
235	/* Only to be called by function printstack. */
236	void print_st(stackitem* stack_head, long counter)
237	{
238	if(stack_head->next != NULL)
239	print_st(stack_head->next, counter+1);
240
241	printf("%ld: ", counter);
242	print_(&stack_head);
243	nl();
244	}
245
246	/* Prints the stack. */
247	extern void printstack(stackitem** stack_head)
248	{
249	if(*stack_head != NULL) {
250	print_st(*stack_head, 1);
251	nl();
252	} else {
253	printerr("Stack empty");
254	}
255	}
256
257	/* If the top element is a reference, determine if it's a reference to a
258	function, and if it is, toss the reference and execute the function. */
259	extern void eval(stackitem** stack_head)
260	{
261	funcp in_func;
262	stackitem* temp= *stack_head;
263
264	if(temp==NULL) {
265	printerr("Stack empty");
266	return;
267	}
268
269	while(temp->type==ref)
270	temp= temp->content.ptr;
271
272	if(temp->type==func) {
273	in_func= (funcp)(temp->content.ptr);
274	toss(stack_head);
275	(*in_func)(stack_head);
276	return;
277	}
278
279	printerr("Couldn't evaluate");
280	}
281
282	/* Make a list. */
283	extern void pack(stackitem** stack_head)
284	{
285	void* delimiter;
286	stackitem iterator, temp, *pack;
287
288	delimiter= (stack_head)->content.ptr; / Get delimiter */
289	toss(stack_head);
290
291	iterator= *stack_head;
292
293	if(iterator==NULL \|\| iterator->content.ptr==delimiter) {
294	temp= NULL;
295	toss(stack_head);
296	} else {
297	/* Search for first delimiter */
298	while(iterator->next!=NULL && iterator->next->content.ptr!=delimiter)
299	iterator= iterator->next;
300
301	/* Extract list */
302	temp= *stack_head;
303	*stack_head= iterator->next;
304	iterator->next= NULL;
305
306	if(stack_head!=NULL && (stack_head)->content.ptr==delimiter)
307	toss(stack_head);
308	}
309
310	/* Push list */
311	pack= malloc(sizeof(stackitem));
312	pack->type= list;
313	pack->content.ptr= temp;
314
315	push(stack_head, pack);
316	}
317
318	/* Parse input. */
319	int stack_read(stackitem** stack_head, hashtbl in_hash, char* in_line)
320	{
321	char temp, rest;
322	int itemp;
323	size_t inlength= strlen(in_line)+1;
324	int convert= 0;
325	static int non_eval_flag= 0;
326
327	temp= malloc(inlength);
328	rest= malloc(inlength);
329
330	do {
331	/* If string */
332	if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
333	push_cstring(stack_head, temp);
334	break;
335	}
336	/* If value */
337	if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
338	push_val(stack_head, itemp);
339	break;
340	}
341	/* Escape ';' with '\' */
342	if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
343	temp[1]= '\0';
344	push_ref(stack_head, in_hash, temp);
345	break;
346	}
347	/* If symbol */
348	if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
349	push_ref(stack_head, in_hash, temp);
350	break;
351	}
352	/* If single char */
353	if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
354	if(*temp==';') {
355	if(!non_eval_flag) {
356	eval(stack_head); /* Evaluate top element */
357	break;
358	}
359
360	push_ref(stack_head, in_hash, ";");
361	break;
362	}
363
364	if(*temp==']') {
365	push_ref(stack_head, in_hash, "[");
366	pack(stack_head);
367	if(non_eval_flag!=0)
368	non_eval_flag--;
369	break;
370	}
371
372	if(*temp=='[') {
373	push_ref(stack_head, in_hash, "[");
374	non_eval_flag++;
375	break;
376	}
377	}
378	} while(0);
379
380
381	free(temp);
382
383	if(convert<2) {
384	free(rest);
385	return 0;
386	}
387
388	stack_read(stack_head, in_hash, rest);
389
390	free(rest);
391	return 1;
392	}
393
394	/* Relocate elements of the list on the stack. */
395	extern void expand(stackitem** stack_head)
396	{
397	stackitem temp, new_head;
398
399	/* Is top element a list? */
400	if((stack_head)==NULL \|\| (stack_head)->type!=list) {
401	printerr("Stack empty or not a list");
402	return;
403	}
404
405	/* The first list element is the new stack head */
406	new_head= temp= (*stack_head)->content.ptr;
407	toss(stack_head);
408
409	if(temp==NULL)
410	return;
411
412	/* Search the end of the list */
413	while(temp->next!=NULL)
414	temp= temp->next;
415
416	/* Connect the the tail of the list with the old stack head */
417	temp->next= *stack_head;
418	stack_head= new_head; / ...and voila! */
419	}
420
421	/* Swap the two top elements on the stack. */
422	extern void swap(stackitem** stack_head)
423	{
424	stackitem* temp= (*stack_head);
425
426	if((*stack_head)==NULL) {
427	printerr("Stack empty");
428	return;
429	}
430
431	if((*stack_head)->next==NULL)
432	return;
433
434	stack_head= (stack_head)->next;
435	temp->next= (*stack_head)->next;
436	(*stack_head)->next= temp;
437	}
438
439	/* Compares two elements by reference. */
440	extern void eq(stackitem** stack_head)
441	{
442	void left, right;
443	int result;
444
445	if((stack_head)==NULL \|\| (stack_head)->next==NULL) {
446	printerr("Not enough elements to compare");
447	return;
448	}
449
450	left= (*stack_head)->content.ptr;
451	swap(stack_head);
452	right= (*stack_head)->content.ptr;
453	result= (left==right);
454
455	toss(stack_head); toss(stack_head);
456	push_val(stack_head, (left==right));
457	}
458
459	/* Negates the top element on the stack. */
460	extern void not(stackitem** stack_head)
461	{
462	int value;
463
464	if((stack_head)==NULL \|\| (stack_head)->type!=value) {
465	printerr("Stack empty or element is not a value");
466	return;
467	}
468
469	value= (*stack_head)->content.val;
470	toss(stack_head);
471	push_val(stack_head, !value);
472	}
473
474	/* Compares the two top elements on the stack and return 0 if they're the
475	same. */
476	extern void neq(stackitem** stack_head)
477	{
478	eq(stack_head);
479	not(stack_head);
480	}
481
482	/* Give a symbol some content. */
483	extern void def(stackitem** stack_head)
484	{
485	stackitem temp, value;
486
487	if(stack_head==NULL \|\| (stack_head)->next==NULL
488	\|\| (*stack_head)->type!=ref) {
489	printerr("Define what?");
490	return;
491	}
492
493	temp= (*stack_head)->content.ptr;
494	value= (*stack_head)->next;
495	temp->content= value->content;
496	value->content.ptr=NULL;
497	temp->type= value->type;
498
499	toss(stack_head); toss(stack_head);
500	}
501
502	/* Quit stack. */
503	extern void quit()
504	{
505	exit(EXIT_SUCCESS);
506	}
507
508	/* Clear stack */
509	extern void clear(stackitem** stack_head)
510	{
511	while(*stack_head!=NULL)
512	toss(stack_head);
513	}
514
515	int main()
516	{
517	stackitem* s= NULL;
518	hashtbl myhash;
519	char in_string[100];
520
521	init_hashtbl(myhash);
522
523	printf("okidok\n ");
524
525	while(fgets(in_string, 100, stdin) != NULL) {
526	stack_read(&s, myhash, in_string);
527	printf("okidok\n ");
528	}
529
530	exit(EXIT_SUCCESS);
531	}
532
533	/* Local Variables: */
534	/* compile-command:"make CFLAGS=\"-Wall -g -rdynamic -ldl\" stack" */
535	/* End: */