cvs/stack/stack.c

/* printf */
#include <stdio.h>
/* EXIT_SUCCESS */
#include <stdlib.h>
/* NULL */
#include <stddef.h>
/* dlopen, dlsym, dlerror */
#include <dlfcn.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;                       /* Tells what kind 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**); /* Function pointer declaration */


/* Initiates 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){                     /* Return position if empty */
    if(*position==NULL)
      return position;
    
    if(strcmp(in_string, (*position)->id)==0) /* Return position 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));
  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 function 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);
    printf("\n");
  } 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;

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

  if(((stackitem*)(*stack_head)->content.ptr)->type==func) {
    in_func= (funcp)((stackitem*)(*stack_head)->content.ptr)->content.ptr;
    toss(stack_head); 
    (*in_func)(stack_head);
    return;
  } else
    printerr("Not a function");
}

/* 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;

  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 ';' */
    if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest)) && *temp==';') {
      eval(stack_head);         /* Evaluate top element */
      break;
    }
  } while(0);


  free(temp);

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

/* 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);
}

/* 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	masse	1.1	/* printf */
2			#include <stdio.h>
3			/* EXIT_SUCCESS */
4			#include <stdlib.h>
5			/* NULL */
6			#include <stddef.h>
7	teddy	1.3	/* dlopen, dlsym, dlerror */
8	masse	1.1	#include <dlfcn.h>
9
10			#define HASHTBLSIZE 65536
11
12			typedef struct stack_item
13			{
14	masse	1.16	enum {
15			value, /* Integer */
16			string,
17			ref, /* Reference (to an element in the hash table) */
18			func, /* Function pointer */
19			symbol,
20			list
21			} type; /* Tells what kind of stack element */
22
23	masse	1.1	union {
24	masse	1.16	void* ptr; /* Pointer to the content */
25			int val; /* ...or an integer */
26			} content; /* Stores a pointer or an integer */
27	masse	1.1
28	masse	1.16	char* id; /* Symbol name */
29			struct stack_item* next; /* Next element */
30	masse	1.1	} stackitem;
31
32
33	masse	1.16	typedef stackitem* hashtbl[HASHTBLSIZE]; /* Hash table declaration */
34			typedef void (funcp)(stackitem); / Function pointer declaration */
35	masse	1.1
36	masse	1.14
37			/* Initiates a newly created hash table. */
38	masse	1.1	void init_hashtbl(hashtbl out_hash)
39			{
40			long i;
41
42			for(i= 0; i<HASHTBLSIZE; i++)
43			out_hash[i]= NULL;
44			}
45
46	masse	1.14	/* Returns a pointer to an element in the hash table. */
47	masse	1.1	stackitem** hash(hashtbl in_hashtbl, const char* in_string)
48			{
49			long i= 0;
50			unsigned long out_hash= 0;
51			char key= 0;
52			stackitem** position;
53
54	masse	1.16	while(1){ /* Hash in_string */
55	masse	1.1	key= in_string[i++];
56			if(key=='\0')
57			break;
58			out_hash= out_hash*32+key;
59			}
60
61			out_hash= out_hash%HASHTBLSIZE;
62			position= &(in_hashtbl[out_hash]);
63
64	masse	1.16	while(1){ /* Return position if empty */
65	masse	1.1	if(*position==NULL)
66			return position;
67
68	masse	1.16	if(strcmp(in_string, (position)->id)==0) / Return position if match */
69	masse	1.1	return position;
70
71	masse	1.16	position= &((position)->next); / Try next */
72	masse	1.1	}
73			}
74
75	masse	1.14	/* Generic push function. */
76	masse	1.1	int push(stackitem** stack_head, stackitem* in_item)
77			{
78			in_item->next= *stack_head;
79			*stack_head= in_item;
80			return 1;
81			}
82
83	masse	1.14	/* Push a value on the stack. */
84	masse	1.1	int push_val(stackitem** stack_head, int in_val)
85			{
86			stackitem* new_item= malloc(sizeof(stackitem));
87			new_item->content.val= in_val;
88			new_item->type= value;
89
90			push(stack_head, new_item);
91			return 1;
92			}
93
94	masse	1.14	/* Copy a string onto the stack. */
95	masse	1.1	int push_cstring(stackitem** stack_head, const char* in_string)
96			{
97			stackitem* new_item= malloc(sizeof(stackitem));
98			new_item->content.ptr= malloc(strlen(in_string)+1);
99			strcpy(new_item->content.ptr, in_string);
100			new_item->type= string;
101
102			push(stack_head, new_item);
103			return 1;
104			}
105
106	masse	1.14	/* Create a new hash entry. */
107	masse	1.1	int mk_hashentry(hashtbl in_hashtbl, stackitem* in_item, const char* id)
108			{
109			in_item->id= malloc(strlen(id)+1);
110
111			strcpy(in_item->id, id);
112			push(hash(in_hashtbl, id), in_item);
113
114			return 1;
115			}
116
117	masse	1.14	/* Define a function a new function in the hash table. */
118	masse	1.1	void def_func(hashtbl in_hashtbl, funcp in_func, const char* id)
119			{
120			stackitem* temp= malloc(sizeof(stackitem));
121
122			temp->type= func;
123			temp->content.ptr= in_func;
124
125			mk_hashentry(in_hashtbl, temp, id);
126			}
127
128	masse	1.14	/* Define a new symbol in the hash table. */
129	masse	1.4	void def_sym(hashtbl in_hashtbl, const char* id)
130			{
131			stackitem* temp= malloc(sizeof(stackitem));
132
133			temp->type= symbol;
134			mk_hashentry(in_hashtbl, temp, id);
135			}
136
137	masse	1.14	/* Push a reference to an entry in the hash table onto the stack. */
138	masse	1.1	int push_ref(stackitem** stack_head, hashtbl in_hash, const char* in_string)
139			{
140	masse	1.6	static void* handle= NULL;
141	masse	1.1	void* symbol;
142	masse	1.6
143	masse	1.1	stackitem* new_item= malloc(sizeof(stackitem));
144			new_item->content.ptr= *hash(in_hash, in_string);
145			new_item->type= ref;
146
147	masse	1.16	if(new_item->content.ptr==NULL) { /* If hash entry empty */
148			if(handle==NULL) /* If no handle */
149	masse	1.9	handle= dlopen(NULL, RTLD_LAZY);
150	masse	1.6
151	masse	1.16	symbol= dlsym(handle, in_string); /* Get function pointer */
152			if(dlerror()==NULL) /* If existing function pointer */
153			def_func(in_hash, symbol, in_string); /* Store function pointer */
154	masse	1.4	else
155	masse	1.16	def_sym(in_hash, in_string); /* Make symbol */
156	masse	1.4
157	masse	1.16	new_item->content.ptr= hash(in_hash, in_string); / XXX */
158	masse	1.4	new_item->type= ref;
159	masse	1.1	}
160
161			push(stack_head, new_item);
162			return 1;
163			}
164
165	masse	1.17	void printerr(const char* in_string) {
166			fprintf(stderr, "Err: %s\n", in_string);
167			}
168
169	masse	1.14	/* Discard the top element of the stack. */
170	masse	1.1	extern void toss(stackitem** stack_head)
171			{
172			stackitem* temp= *stack_head;
173
174	masse	1.17	if((*stack_head)==NULL) {
175			printerr("Stack empty");
176	masse	1.7	return;
177	masse	1.17	}
178	masse	1.7
179			if((*stack_head)->type==string)
180			free((*stack_head)->content.ptr);
181
182	masse	1.1	stack_head= (stack_head)->next;
183			free(temp);
184			}
185
186	masse	1.14	/* Print newline. */
187	masse	1.8	extern void nl()
188			{
189			printf("\n");
190			}
191	masse	1.1
192	masse	1.14	/* Prints the top element of the stack. */
193	masse	1.11	void print_(stackitem** stack_head)
194	masse	1.8	{
195	masse	1.17	if((*stack_head)==NULL) {
196			printerr("Stack empty");
197	masse	1.8	return;
198	masse	1.17	}
199	masse	1.1
200	masse	1.8	switch((*stack_head)->type) {
201	teddy	1.2	case value:
202	masse	1.8	printf("%d", (*stack_head)->content.val);
203	teddy	1.2	break;
204			case string:
205	masse	1.8	printf("%s", (char)(stack_head)->content.ptr);
206	teddy	1.2	break;
207			case ref:
208	masse	1.8	printf("%s", ((stackitem)(stack_head)->content.ptr)->id);
209	masse	1.6	break;
210	masse	1.4	case symbol:
211	masse	1.7	default:
212	masse	1.8	printf("%p", (*stack_head)->content.ptr);
213	teddy	1.2	break;
214			}
215	masse	1.1	}
216
217	masse	1.14	/* Prints the top element of the stack and then discards it. */
218	masse	1.8	extern void print(stackitem** stack_head)
219			{
220	masse	1.11	print_(stack_head);
221	masse	1.8	toss(stack_head);
222			}
223
224	masse	1.14	/* Only to be called by function printstack. */
225	masse	1.8	void print_st(stackitem* stack_head, long counter)
226			{
227			if(stack_head->next != NULL)
228			print_st(stack_head->next, counter+1);
229
230			printf("%ld: ", counter);
231	masse	1.11	print_(&stack_head);
232	masse	1.8	nl();
233			}
234
235	masse	1.14	/* Prints the stack. */
236	masse	1.1	extern void printstack(stackitem** stack_head)
237			{
238			if(*stack_head != NULL) {
239			print_st(*stack_head, 1);
240			printf("\n");
241	masse	1.17	} else {
242			printerr("Stack empty");
243	masse	1.1	}
244			}
245
246	masse	1.14	/* If the top element is a reference, determine if it's a reference to a
247	masse	1.16	function, and if it is, toss the reference and execute the function. */
248	masse	1.1	extern void eval(stackitem** stack_head)
249			{
250			funcp in_func;
251
252	masse	1.17	if((stack_head)==NULL \|\| (stack_head)->type!=ref) {
253			printerr("Stack empty or not a reference");
254	masse	1.1	return;
255	masse	1.17	}
256	masse	1.1
257			if(((stackitem)(stack_head)->content.ptr)->type==func) {
258			in_func= (funcp)((stackitem)(stack_head)->content.ptr)->content.ptr;
259			toss(stack_head);
260			(*in_func)(stack_head);
261			return;
262	masse	1.17	} else
263			printerr("Not a function");
264	masse	1.1	}
265
266	masse	1.14	/* Parse input. */
267	masse	1.1	int stack_read(stackitem** stack_head, hashtbl in_hash, char* in_line)
268			{
269			char temp, rest;
270			int itemp;
271			size_t inlength= strlen(in_line)+1;
272			int convert= 0;
273
274			temp= malloc(inlength);
275			rest= malloc(inlength);
276
277	masse	1.15	do {
278	masse	1.16	/* If string */
279	masse	1.15	if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
280			push_cstring(stack_head, temp);
281			break;
282			}
283	masse	1.16	/* If value */
284	masse	1.15	if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
285			push_val(stack_head, itemp);
286			break;
287			}
288	masse	1.16	/* Escape ';' with '\' */
289	masse	1.15	if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
290			temp[1]= '\0';
291			push_ref(stack_head, in_hash, temp);
292			break;
293			}
294	masse	1.16	/* If symbol */
295	masse	1.15	if((convert= sscanf(in_line, "%[^ ;\n\r]%[^\n\r]", temp, rest))) {
296			push_ref(stack_head, in_hash, temp);
297			break;
298			}
299	masse	1.16	/* If ';' */
300	masse	1.15	if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest)) && *temp==';') {
301	masse	1.16	eval(stack_head); /* Evaluate top element */
302	masse	1.15	break;
303			}
304			} while(0);
305
306	masse	1.1
307			free(temp);
308
309			if(convert<2) {
310			free(rest);
311			return 0;
312			}
313
314			stack_read(stack_head, in_hash, rest);
315
316			free(rest);
317			return 1;
318			}
319
320	masse	1.14	/* Make a list. */
321	masse	1.7	extern void pack(stackitem** stack_head)
322			{
323			void* delimiter;
324			stackitem iterator, temp, *pack;
325
326	masse	1.17	if((*stack_head)==NULL) {
327			printerr("Stack empty");
328	masse	1.7	return;
329	masse	1.17	}
330	masse	1.7
331	masse	1.16	delimiter= (stack_head)->content.ptr; / Get delimiter */
332	masse	1.7	toss(stack_head);
333
334			iterator= *stack_head;
335
336	masse	1.16	/* Search for first delimiter */
337	masse	1.7	while(iterator->next!=NULL && iterator->next->content.ptr!=delimiter)
338			iterator= iterator->next;
339
340	masse	1.16	/* Extract list */
341	masse	1.7	temp= *stack_head;
342			*stack_head= iterator->next;
343			iterator->next= NULL;
344
345			if(stack_head!=NULL && (stack_head)->content.ptr==delimiter)
346			toss(stack_head);
347
348	masse	1.16	/* Push list */
349	masse	1.7	pack= malloc(sizeof(stackitem));
350			pack->type= list;
351			pack->content.ptr= temp;
352
353			push(stack_head, pack);
354			}
355	masse	1.1
356	masse	1.16	/* Relocate elements of the list on the stack. */
357	masse	1.8	extern void expand(stackitem** stack_head)
358	masse	1.1	{
359	masse	1.8	stackitem temp, new_head;
360
361	masse	1.16	/* Is top element a list? */
362	masse	1.17	if((stack_head)==NULL \|\| (stack_head)->type!=list) {
363			printerr("Stack empty or not a list");
364	masse	1.8	return;
365	masse	1.17	}
366	masse	1.8
367	masse	1.16	/* The first list element is the new stack head */
368	masse	1.8	new_head= temp= (*stack_head)->content.ptr;
369			toss(stack_head);
370
371	masse	1.16	/* Search the end of the list */
372	masse	1.8	while(temp->next!=NULL)
373			temp= temp->next;
374
375	masse	1.16	/* Connect the the tail of the list with the old stack head */
376	masse	1.8	temp->next= *stack_head;
377	masse	1.16	stack_head= new_head; / ...and voila! */
378	teddy	1.5	}
379
380	masse	1.14	/* Swap the two top elements on the stack. */
381	masse	1.10	extern void swap(stackitem** stack_head)
382			{
383			stackitem* temp= (*stack_head);
384
385	masse	1.17	if((*stack_head)==NULL) {
386			printerr("Stack empty");
387			return;
388			}
389
390			if((*stack_head)->next==NULL)
391	masse	1.10	return;
392
393			stack_head= (stack_head)->next;
394			temp->next= (*stack_head)->next;
395			(*stack_head)->next= temp;
396			}
397	masse	1.11
398	masse	1.14	/* Compares two elements by reference. */
399	masse	1.11	extern void eq(stackitem** stack_head)
400			{
401			void left, right;
402			int result;
403
404	masse	1.17	if((stack_head)==NULL \|\| (stack_head)->next==NULL) {
405			printerr("Not enough elements to compare");
406	masse	1.11	return;
407	masse	1.17	}
408	masse	1.11
409			left= (*stack_head)->content.ptr;
410	masse	1.12	swap(stack_head);
411			right= (*stack_head)->content.ptr;
412	masse	1.11	result= (left==right);
413
414			toss(stack_head); toss(stack_head);
415			push_val(stack_head, (left==right));
416			}
417
418	masse	1.14	/* Negates the top element on the stack. */
419	masse	1.11	extern void not(stackitem** stack_head)
420			{
421			int value;
422
423	masse	1.17	if((stack_head)==NULL \|\| (stack_head)->type!=value) {
424			printerr("Stack empty or element is not a value");
425	masse	1.11	return;
426	masse	1.17	}
427	masse	1.11
428			value= (*stack_head)->content.val;
429			toss(stack_head);
430			push_val(stack_head, !value);
431			}
432
433	masse	1.14	/* Compares the two top elements on the stack and return 0 if they're the
434			same. */
435	masse	1.11	extern void neq(stackitem** stack_head)
436			{
437			eq(stack_head);
438			not(stack_head);
439			}
440	masse	1.12
441	masse	1.14	/* Give a symbol some content. */
442	masse	1.12	extern void def(stackitem** stack_head)
443			{
444			stackitem temp, value;
445
446			if(stack_head==NULL \|\| (stack_head)->next==NULL
447	masse	1.17	\|\| (*stack_head)->type!=ref) {
448			printerr("Define what?");
449	masse	1.12	return;
450	masse	1.17	}
451	masse	1.12
452			temp= (*stack_head)->content.ptr;
453			value= (*stack_head)->next;
454			temp->content= value->content;
455			value->content.ptr=NULL;
456			temp->type= value->type;
457
458			toss(stack_head); toss(stack_head);
459			}
460	masse	1.10
461	masse	1.14	/* Quit stack. */
462	teddy	1.5	extern void quit()
463			{
464			exit(EXIT_SUCCESS);
465	masse	1.1	}
466
467			int main()
468			{
469			stackitem* s= NULL;
470			hashtbl myhash;
471			char in_string[100];
472
473			init_hashtbl(myhash);
474
475			printf("okidok\n ");
476
477			while(fgets(in_string, 100, stdin) != NULL) {
478			stack_read(&s, myhash, in_string);
479			printf("okidok\n ");
480			}
481
482	masse	1.10	exit(EXIT_SUCCESS);
483	masse	1.1	}
484	teddy	1.3
485			/* Local Variables: */
486			/* compile-command:"make CFLAGS=\"-Wall -g -rdynamic -ldl\" stack" */
487			/* End: */