/[cvs]/stack/stack.c
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revision 1.19 by masse, Sat Feb 2 14:50:44 2002 UTC revision 1.30 by teddy, Tue Feb 5 12:33:21 2002 UTC
# Line 11  Line 11 
11    
12  #define HASHTBLSIZE 65536  #define HASHTBLSIZE 65536
13    
14  typedef struct stack_item  /* First, define some types. */
15  {  
16    /* A value of some type */
17    typedef struct {
18    enum {    enum {
19      value,                      /* Integer */      integer,
20      string,      string,
21      ref,                        /* Reference (to an element in the      ref,                        /* Reference (to an element in the
22                                     hash table) */                                     hash table) */
23      func,                       /* Function pointer */      func,                       /* Function pointer */
24      symbol,      symb,
25      list      list
26    } type;                       /* Type of stack element */    } type;                       /* Type of stack element */
27    
28    union {    union {
29      void* ptr;                  /* Pointer to the content */      void *ptr;                  /* Pointer to the content */
30      int val;                    /* ...or an integer */      int val;                    /* ...or an integer */
31    } content;                    /* Stores a pointer or an integer */    } content;                    /* Stores a pointer or an integer */
32    
33    char* id;                     /* Symbol name */    int refcount;                 /* Reference counter */
34    struct stack_item* next;      /* Next element */  
35  } stackitem;  } value;
36    
37    /* A symbol with a name and possible value */
38    /* (These do not need reference counters, they are kept unique by
39       hashing.) */
40    typedef struct symbol_struct {
41      char *id;                     /* Symbol name */
42      value *val;                   /* The value (if any) bound to it */
43      struct symbol_struct *next;   /* In case of hashing conflicts, a */
44    } symbol;                       /* symbol is a kind of stack item. */
45    
46  typedef stackitem* hashtbl[HASHTBLSIZE]; /* Hash table declaration */  /* A type for a hash table for symbols */
47  typedef void (*funcp)(stackitem**); /* funcp is a pointer to a  typedef symbol *hashtbl[HASHTBLSIZE]; /* Hash table declaration */
                                        void function (stackitem **) */  
48    
49  /* Initialize a newly created hash table. */  /* An item (value) on a stack */
50  void init_hashtbl(hashtbl out_hash)  typedef struct stackitem_struct
51    {
52      value *item;                  /* The value on the stack */
53      struct stackitem_struct *next; /* Next item */
54    } stackitem;
55    
56    /* An environment; gives access to the stack and a hash table of
57       defined symbols */
58    typedef struct {
59      stackitem *head;              /* Head of the stack */
60      hashtbl symbols;              /* Hash table of all variable bindings */
61    } environment;
62    
63    /* A type for pointers to external functions */
64    typedef void (*funcp)(environment *); /* funcp is a pointer to a void
65                                             function (environment *) */
66    
67    /* Initialize a newly created environment */
68    void init_env(environment *env)
69  {  {
70    long i;    long i;
71    
72    for(i= 0; i<HASHTBLSIZE; i++)    for(i= 0; i<HASHTBLSIZE; i++)
73      out_hash[i]= NULL;      env->symbols[i]= NULL;
74  }  }
75    
76  /* Returns a pointer to an element in the hash table. */  /* Returns a pointer to a pointer to an element in the hash table. */
77  stackitem** hash(hashtbl in_hashtbl, const char* in_string)  symbol **hash(hashtbl in_hashtbl, const char *in_string)
78  {  {
79    long i= 0;    long i= 0;
80    unsigned long out_hash= 0;    unsigned long out_hash= 0;
81    char key= '\0';    char key= '\0';
82    stackitem** position;    symbol **position;
83        
84    while(1){                     /* Hash in_string */    while(1){                     /* Hash in_string */
85      key= in_string[i++];      key= in_string[i++];
# Line 64  stackitem** hash(hashtbl in_hashtbl, con Line 91  stackitem** hash(hashtbl in_hashtbl, con
91    out_hash= out_hash%HASHTBLSIZE;    out_hash= out_hash%HASHTBLSIZE;
92    position= &(in_hashtbl[out_hash]);    position= &(in_hashtbl[out_hash]);
93    
94    while(position != NULL){    while(1){
95      if(*position==NULL)         /* If empty */      if(*position==NULL)         /* If empty */
96        return position;        return position;
97            
# Line 73  stackitem** hash(hashtbl in_hashtbl, con Line 100  stackitem** hash(hashtbl in_hashtbl, con
100    
101      position= &((*position)->next); /* Try next */      position= &((*position)->next); /* Try next */
102    }    }
   return NULL;                  /* end of list reached without finding  
                                    an empty position */  
103  }  }
104    
105  /* Generic push function. */  /* Generic push function. */
# Line 85  int push(stackitem** stack_head, stackit Line 110  int push(stackitem** stack_head, stackit
110    return 1;    return 1;
111  }  }
112    
113  /* Push a value on the stack. */  /* Push a value onto the stack */
114  int push_val(stackitem** stack_head, int in_val)  void push_val(stackitem **stack_head, value *val)
115  {  {
116    stackitem* new_item= malloc(sizeof(stackitem));    stackitem *new_item= malloc(sizeof(stackitem));
117    assert(new_item != NULL);    new_item->item= val;
118    new_item->content.val= in_val;    val->refcount++;
   new_item->type= value;  
   
119    push(stack_head, new_item);    push(stack_head, new_item);
   return 1;  
120  }  }
121    
122  /* Copy a string onto the stack. */  /* Push an integer onto the stack. */
123  int push_cstring(stackitem** stack_head, const char* in_string)  int push_int(stackitem **stack_head, int in_val)
124  {  {
125    stackitem* new_item= malloc(sizeof(stackitem));    value *new_value= malloc(sizeof(value));
126    new_item->content.ptr= malloc(strlen(in_string)+1);    stackitem *new_item= malloc(sizeof(stackitem));
127    strcpy(new_item->content.ptr, in_string);    new_item->item= new_value;
128    new_item->type= string;    
129      new_value->content.val= in_val;
130      new_value->type= integer;
131      new_value->refcount=1;
132    
133    push(stack_head, new_item);    push(stack_head, new_item);
134    return 1;    return 1;
135  }  }
136    
137  /* Create a new hash entry. */  /* Copy a string onto the stack. */
138  int mk_hashentry(hashtbl in_hashtbl, stackitem* in_item, const char* id)  int push_cstring(stackitem **stack_head, const char *in_string)
139  {  {
140    in_item->id= malloc(strlen(id)+1);    value *new_value= malloc(sizeof(value));
141      stackitem *new_item= malloc(sizeof(stackitem));
142    strcpy(in_item->id, id);    new_item->item=new_value;
143    push(hash(in_hashtbl, id), in_item);  
144      new_value->content.ptr= malloc(strlen(in_string)+1);
145      strcpy(new_value->content.ptr, in_string);
146      new_value->type= string;
147      new_value->refcount=1;
148    
149      push(stack_head, new_item);
150    return 1;    return 1;
151  }  }
152    
153  /* Define a new function in the hash table. */  /* Push a symbol onto the stack. */
154  void def_func(hashtbl in_hashtbl, funcp in_func, const char* id)  int push_sym(environment *env, const char *in_string)
155  {  {
156    stackitem* temp= malloc(sizeof(stackitem));    stackitem *new_item;          /* The new stack item */
157      /* ...which will contain... */
158      value *new_value;             /* A new symbol value */
159      /* ...which might point to... */
160      symbol **new_symbol;          /* (if needed) A new actual symbol */
161      /* ...which, if possible, will be bound to... */
162      value *new_fvalue;            /* (if needed) A new function value */
163      /* ...which will point to... */
164      void *funcptr;                /* A function pointer */
165    
166      static void *handle= NULL;    /* Dynamic linker handle */
167    
168      /* Create a new stack item containing a new value */
169      new_item= malloc(sizeof(stackitem));
170      new_value= malloc(sizeof(value));
171      new_item->item=new_value;
172    
173      /* The new value is a symbol */
174      new_value->type= symb;
175      new_value->refcount= 1;
176    
177      /* Look up the symbol name in the hash table */
178      new_symbol= hash(env->symbols, in_string);
179      new_value->content.ptr= *new_symbol;
180    
181      if(*new_symbol==NULL) { /* If symbol was undefined */
182    
183        /* Create a new symbol */
184        (*new_symbol)= malloc(sizeof(symbol));
185        (*new_symbol)->val= NULL;   /* undefined value */
186        (*new_symbol)->next= NULL;
187        (*new_symbol)->id= malloc(strlen(in_string)+1);
188        strcpy((*new_symbol)->id, in_string);
189    
190    temp->type= func;      /* Intern the new symbol in the hash table */
191    temp->content.ptr= in_func;      new_value->content.ptr= *new_symbol;
   
   mk_hashentry(in_hashtbl, temp, id);  
 }  
192    
193  /* Define a new symbol in the hash table. */      /* Try to load the symbol name as an external function, to see if
194  void def_sym(hashtbl in_hashtbl, const char* id)         we should bind the symbol to a new function pointer value */
 {  
   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 */  
195      if(handle==NULL)            /* If no handle */      if(handle==NULL)            /* If no handle */
196        handle= dlopen(NULL, RTLD_LAZY);            handle= dlopen(NULL, RTLD_LAZY);
197    
198      symbol= dlsym(handle, in_string); /* Get function pointer */      funcptr= dlsym(handle, in_string); /* Get function pointer */
199      if(dlerror()==NULL)         /* If existing function pointer */      if(dlerror()==NULL) {       /* If a function was found */
200        def_func(in_hash, symbol, in_string); /* Store function pointer */        new_fvalue= malloc(sizeof(value)); /* Create a new value */
201      else        new_fvalue->type=func;    /* The new value is a function pointer */
202        def_sym(in_hash, in_string); /* Make symbol */        new_fvalue->content.ptr=funcptr; /* Store function pointer */
203                (*new_symbol)->val= new_fvalue; /* Bind the symbol to the new
204      new_item->content.ptr= *hash(in_hash, in_string); /* XXX */                                           function value */
205      new_item->type= ref;        new_fvalue->refcount= 1;
206        }
207    }    }
208      push(&(env->head), new_item);
   push(stack_head, new_item);  
209    return 1;    return 1;
210  }  }
211    
# Line 172  void printerr(const char* in_string) { Line 213  void printerr(const char* in_string) {
213    fprintf(stderr, "Err: %s\n", in_string);    fprintf(stderr, "Err: %s\n", in_string);
214  }  }
215    
216    /* Throw away a value */
217    void free_val(value *val){
218      stackitem *item, *temp;
219    
220      val->refcount--;              /* Decrease the reference count */
221      if(val->refcount == 0){
222        switch (val->type){         /* and free the contents if necessary */
223        case string:
224          free(val->content.ptr);
225        case list:                  /* lists needs to be freed recursively */
226          item=val->content.ptr;
227          while(item != NULL) {     /* for all stack items */
228            free_val(item->item);   /* free the value */
229            temp=item->next;        /* save next ptr */
230            free(item);             /* free the stackitem */
231            item=temp;              /* go to next stackitem */
232          }
233          free(val);                /* Free the actual list value */
234          break;
235        default:
236          break;
237        }
238      }
239    }
240    
241  /* Discard the top element of the stack. */  /* Discard the top element of the stack. */
242  extern void toss(stackitem** stack_head)  extern void toss(environment *env)
243  {  {
244    stackitem* temp= *stack_head;    stackitem *temp= env->head;
245    
246    if((*stack_head)==NULL) {    if((env->head)==NULL) {
247      printerr("Stack empty");      printerr("Stack empty");
248      return;      return;
249    }    }
250        
251    if((*stack_head)->type==string)    free_val(env->head->item);    /* Free the value */
252      free((*stack_head)->content.ptr);    env->head= env->head->next;   /* Remove the top stack item */
253      free(temp);                   /* Free the old top stack item */
   *stack_head= (*stack_head)->next;  
   free(temp);  
254  }  }
255    
256  /* Print newline. */  /* Print newline. */
# Line 196  extern void nl() Line 260  extern void nl()
260  }  }
261    
262  /* Prints the top element of the stack. */  /* Prints the top element of the stack. */
263  void print_(stackitem** stack_head)  void print_h(stackitem *stack_head)
264  {  {
265    if((*stack_head)==NULL) {  
266      if(stack_head==NULL) {
267      printerr("Stack empty");      printerr("Stack empty");
268      return;      return;
269    }    }
270    
271    switch((*stack_head)->type) {    switch(stack_head->item->type) {
272    case value:    case integer:
273      printf("%d", (*stack_head)->content.val);      printf("%d", stack_head->item->content.val);
274      break;      break;
275    case string:    case string:
276      printf("%s", (char*)(*stack_head)->content.ptr);      printf("\"%s\"", (char*)stack_head->item->content.ptr);
277      break;      break;
278    case ref:    case symb:
279      printf("%s", ((stackitem*)(*stack_head)->content.ptr)->id);      printf("'%s'", ((symbol *)(stack_head->item->content.ptr))->id);
280      break;      break;
   case symbol:  
281    default:    default:
282      printf("%p", (*stack_head)->content.ptr);      printf("%p", (funcp)(stack_head->item->content.ptr));
283      break;      break;
284    }    }
285  }  }
286    
287    extern void print_(environment *env) {
288      print_h(env->head);
289    }
290    
291  /* Prints the top element of the stack and then discards it. */  /* Prints the top element of the stack and then discards it. */
292  extern void print(stackitem** stack_head)  extern void print(environment *env)
293  {  {
294    print_(stack_head);    print_(env);
295    toss(stack_head);    toss(env);
296  }  }
297    
298  /* Only to be called by function printstack. */  /* Only to be called by function printstack. */
299  void print_st(stackitem* stack_head, long counter)  void print_st(stackitem *stack_head, long counter)
300  {  {
301    if(stack_head->next != NULL)    if(stack_head->next != NULL)
302      print_st(stack_head->next, counter+1);      print_st(stack_head->next, counter+1);
   
303    printf("%ld: ", counter);    printf("%ld: ", counter);
304    print_(&stack_head);    print_h(stack_head);
305    nl();    nl();
306  }  }
307    
308    
309    
310  /* Prints the stack. */  /* Prints the stack. */
311  extern void printstack(stackitem** stack_head)  extern void printstack(environment *env)
312  {  {
313    if(*stack_head != NULL) {    if(env->head != NULL) {
314      print_st(*stack_head, 1);      print_st(env->head, 1);
315      printf("\n");      nl();
316    } else {    } else {
317      printerr("Stack empty");      printerr("Stack empty");
318    }    }
319  }  }
320    
321  /* If the top element is a reference, determine if it's a reference to a  /* Swap the two top elements on the stack. */
322     function, and if it is, toss the reference and execute the function. */  extern void swap(environment *env)
 extern void eval(stackitem** stack_head)  
323  {  {
324    funcp in_func;    stackitem *temp= env->head;
325      
326    if((*stack_head)==NULL || (*stack_head)->type!=ref) {    if((env->head)==NULL) {
327      printerr("Stack empty or not a reference");      printerr("Stack empty");
328      return;      return;
329    }    }
330    
331    if(((stackitem*)(*stack_head)->content.ptr)->type==func) {    if(env->head->next==NULL) {
332      in_func= (funcp)((stackitem*)(*stack_head)->content.ptr)->content.ptr;      printerr("Not enough arguments");
     toss(stack_head);  
     (*in_func)(stack_head);  
333      return;      return;
334    } else    }
     printerr("Not a function");  
 }  
335    
336  /* Make a list. */    env->head= env->head->next;
337  extern void pack(stackitem** stack_head)    temp->next= env->head->next;
338      env->head->next= temp;
339    }
340    
341    stackitem* copy(stackitem* in_item)
342  {  {
343    void* delimiter;    stackitem *out_item= malloc(sizeof(stackitem));
   stackitem *iterator, *temp, *pack;  
344    
345    if((*stack_head)==NULL) {    memcpy(out_item, in_item, sizeof(stackitem));
346      out_item->next= NULL;
347    
348      return out_item;
349    }
350    
351    
352    /* If the top element is a symbol, determine if it's bound to a
353       function value, and if it is, toss the symbol and execute the
354       function. */
355    extern void eval(environment *env)
356    {
357      funcp in_func;
358      value* val;
359      if(env->head==NULL) {
360      printerr("Stack empty");      printerr("Stack empty");
361      return;      return;
362    }    }
363    
364    delimiter= (*stack_head)->content.ptr; /* Get delimiter */    /* if it's a symbol */
365    toss(stack_head);    if(env->head->item->type==symb) {
366    
367    iterator= *stack_head;      /* If it's not bound to anything */
368        if (((symbol *)(env->head->item->content.ptr))->val == NULL) {
369          printerr("Unbound variable");
370          return;
371        }
372        
373        /* If it contains a function */
374        if (((symbol *)(env->head->item->content.ptr))->val->type == func) {
375          in_func=
376            (funcp)(((symbol *)(env->head->item->content.ptr))->val->content.ptr);
377          toss(env);
378          (*in_func)(env);          /* Run the function */
379          return;
380        } else {                    /* If it's not a function */
381          val=((symbol *)(env->head->item->content.ptr))->val;
382          toss(env);                /* toss the symbol */
383          push_val(&(env->head), val); /* Return its bound value */
384        }
385      }
386    
387    /* Search for first delimiter */    /* If it's a lone function value, run it */
388    while(iterator->next!=NULL && iterator->next->content.ptr!=delimiter)    if(env->head->item->type==func) {
389      iterator= iterator->next;      in_func= (funcp)(env->head->item->content.ptr);
390        toss(env);
391    /* Extract list */      (*in_func)(env);
392    temp= *stack_head;      return;
393    *stack_head= iterator->next;    }
394    iterator->next= NULL;  
395      }
396    if(*stack_head!=NULL && (*stack_head)->content.ptr==delimiter)  
397      toss(stack_head);  /* Make a list. */
398    extern void pack(environment *env)
399    {
400      void* delimiter;
401      stackitem *iterator, *temp;
402      value *pack;
403    
404      delimiter= env->head->item->content.ptr; /* Get delimiter */
405      toss(env);
406    
407      iterator= env->head;
408    
409      if(iterator==NULL || iterator->item->content.ptr==delimiter) {
410        temp= NULL;
411        toss(env);
412      } else {
413        /* Search for first delimiter */
414        while(iterator->next!=NULL
415              && iterator->next->item->content.ptr!=delimiter)
416          iterator= iterator->next;
417        
418        /* Extract list */
419        temp= env->head;
420        env->head= iterator->next;
421        iterator->next= NULL;
422        
423        if(env->head!=NULL)
424          toss(env);
425      }
426    
427    /* Push list */    /* Push list */
428    pack= malloc(sizeof(stackitem));    pack= malloc(sizeof(value));
429    pack->type= list;    pack->type= list;
430    pack->content.ptr= temp;    pack->content.ptr= temp;
431      pack->refcount= 1;
432    
433      temp= malloc(sizeof(stackitem));
434      temp->item= pack;
435    
436    push(stack_head, pack);    push(&(env->head), temp);
437  }  }
438    
439  /* Parse input. */  /* Parse input. */
440  int stack_read(stackitem** stack_head, hashtbl in_hash, char* in_line)  int stack_read(environment *env, char *in_line)
441  {  {
442    char *temp, *rest;    char *temp, *rest;
443    int itemp;    int itemp;
444    size_t inlength= strlen(in_line)+1;    size_t inlength= strlen(in_line)+1;
445    int convert= 0;    int convert= 0;
446      static int non_eval_flag= 0;
447    
448    temp= malloc(inlength);    temp= malloc(inlength);
449    rest= malloc(inlength);    rest= malloc(inlength);
# Line 319  int stack_read(stackitem** stack_head, h Line 451  int stack_read(stackitem** stack_head, h
451    do {    do {
452      /* If string */      /* If string */
453      if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {      if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
454        push_cstring(stack_head, temp);        push_cstring(&(env->head), temp);
455        break;        break;
456      }      }
457      /* If value */      /* If integer */
458      if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {      if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
459        push_val(stack_head, itemp);        push_int(&(env->head), itemp);
460        break;        break;
461      }      }
462      /* Escape ';' with '\' */      /* Escape ';' with '\' */
463      if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {      if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
464        temp[1]= '\0';        temp[1]= '\0';
465        push_ref(stack_head, in_hash, temp);        push_sym(env, temp);
466        break;        break;
467      }      }
468      /* If symbol */      /* If symbol */
469      if((convert= sscanf(in_line, "%[^] ;\n\r]%[^\n\r]", temp, rest))) {      if((convert= sscanf(in_line, "%[^][ ;\n\r_]%[^\n\r]", temp, rest))) {
470          push_ref(stack_head, in_hash, temp);          push_sym(env, temp);
471          break;          break;
472      }      }
473      /* If single char */      /* If single char */
474      if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {      if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
475        if(*temp==';') {        if(*temp==';') {
476          eval(stack_head);               /* Evaluate top element */          if(!non_eval_flag) {
477              eval(env);            /* Evaluate top element */
478              break;
479            }
480            
481            push_sym(env, ";");
482          break;          break;
483        }        }
484    
485        if(*temp==']') {        if(*temp==']') {
486          push_ref(stack_head, in_hash, "[");          push_sym(env, "[");
487          pack(stack_head);          pack(env);
488            if(non_eval_flag!=0)
489              non_eval_flag--;
490            break;
491          }
492    
493          if(*temp=='[') {
494            push_sym(env, "[");
495            non_eval_flag++;
496          break;          break;
497        }        }
498      }      }
# Line 361  int stack_read(stackitem** stack_head, h Line 506  int stack_read(stackitem** stack_head, h
506      return 0;      return 0;
507    }    }
508        
509    stack_read(stack_head, in_hash, rest);    stack_read(env, rest);
510        
511    free(rest);    free(rest);
512    return 1;    return 1;
513  }  }
514    
515  /* Relocate elements of the list on the stack. */  /* Relocate elements of the list on the stack. */
516  extern void expand(stackitem** stack_head)  extern void expand(environment *env)
517  {  {
518    stackitem *temp, *new_head;    stackitem *temp, *new_head;
519    
520    /* Is top element a list? */    /* Is top element a list? */
521    if((*stack_head)==NULL || (*stack_head)->type!=list) {    if(env->head==NULL || env->head->item->type!=list) {
522      printerr("Stack empty or not a list");      printerr("Stack empty or not a list");
523      return;      return;
524    }    }
525    
526    /* The first list element is the new stack head */    /* The first list element is the new stack head */
527    new_head= temp= (*stack_head)->content.ptr;    new_head= temp= env->head->item->content.ptr;
   toss(stack_head);  
528    
529    /* Search the end of the list */    env->head->item->refcount++;
530      toss(env);
531    
532      /* Find the end of the list */
533    while(temp->next!=NULL)    while(temp->next!=NULL)
534      temp= temp->next;      temp= temp->next;
535    
536    /* Connect the the tail of the list with the old stack head */    /* Connect the tail of the list with the old stack head */
537    temp->next= *stack_head;    temp->next= env->head;
538    *stack_head= new_head;        /* ...and voila! */    env->head= new_head;          /* ...and voila! */
 }  
539    
540  /* 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;  
 }  
541    
542  /* Compares two elements by reference. */  /* Compares two elements by reference. */
543  extern void eq(stackitem** stack_head)  extern void eq(environment *env)
544  {  {
545    void *left, *right;    void *left, *right;
546    int result;    int result;
547    
548    if((*stack_head)==NULL || (*stack_head)->next==NULL) {    if((env->head)==NULL || env->head->next==NULL) {
549      printerr("Not enough elements to compare");      printerr("Not enough elements to compare");
550      return;      return;
551    }    }
552    
553    left= (*stack_head)->content.ptr;    left= env->head->item->content.ptr;
554    swap(stack_head);    swap(env);
555    right= (*stack_head)->content.ptr;    right= env->head->item->content.ptr;
556    result= (left==right);    result= (left==right);
557        
558    toss(stack_head); toss(stack_head);    toss(env); toss(env);
559    push_val(stack_head, (left==right));    push_int(&(env->head), result);
560  }  }
561    
562  /* Negates the top element on the stack. */  /* Negates the top element on the stack. */
563  extern void not(stackitem** stack_head)  extern void not(environment *env)
564  {  {
565    int value;    int val;
566    
567    if((*stack_head)==NULL || (*stack_head)->type!=value) {    if((env->head)==NULL || env->head->item->type!=integer) {
568      printerr("Stack empty or element is not a value");      printerr("Stack empty or element is not a integer");
569      return;      return;
570    }    }
571    
572    value= (*stack_head)->content.val;    val= env->head->item->content.val;
573    toss(stack_head);    toss(env);
574    push_val(stack_head, !value);    push_int(&(env->head), !val);
575  }  }
576    
577  /* Compares the two top elements on the stack and return 0 if they're the  /* Compares the two top elements on the stack and return 0 if they're the
578     same. */     same. */
579  extern void neq(stackitem** stack_head)  extern void neq(environment *env)
580  {  {
581    eq(stack_head);    eq(env);
582    not(stack_head);    not(env);
583  }  }
584    
585  /* Give a symbol some content. */  /* Give a symbol some content. */
586  extern void def(stackitem** stack_head)  extern void def(environment *env)
587  {  {
588    stackitem *temp, *value;    symbol *sym;
589    
590    if(*stack_head==NULL || (*stack_head)->next==NULL    /* Needs two values on the stack, the top one must be a symbol */
591       || (*stack_head)->type!=ref) {    if(env->head==NULL || env->head->next==NULL
592         || env->head->item->type!=symb) {
593      printerr("Define what?");      printerr("Define what?");
594      return;      return;
595    }    }
596    
597    temp= (*stack_head)->content.ptr;    /* long names are a pain */
598    value= (*stack_head)->next;    sym=env->head->item->content.ptr;
599    temp->content= value->content;  
600    value->content.ptr=NULL;    /* if the symbol was bound to something else, throw it away */
601    temp->type= value->type;    if(sym->val != NULL)
602        free_val(sym->val);
603    
604      /* Bind the symbol to the value */
605      sym->val= env->head->next->item;
606      sym->val->refcount++;         /* Increase the reference counter */
607    
608    toss(stack_head); toss(stack_head);    toss(env); toss(env);
609  }  }
610    
611  /* Quit stack. */  /* Quit stack. */
612  extern void quit()  extern void quit(environment *env)
613  {  {
614    exit(EXIT_SUCCESS);    exit(EXIT_SUCCESS);
615  }  }
616    
617    /* Clear stack */
618    extern void clear(environment *env)
619    {
620      while(env->head!=NULL)
621        toss(env);
622    }
623    
624  int main()  int main()
625  {  {
626    stackitem* s= NULL;    environment myenv;
   hashtbl myhash;  
627    char in_string[100];    char in_string[100];
628    
629    init_hashtbl(myhash);    init_env(&myenv);
630    
631    printf("okidok\n ");    printf("okidok\n ");
632    
633    while(fgets(in_string, 100, stdin) != NULL) {    while(fgets(in_string, 100, stdin) != NULL) {
634      stack_read(&s, myhash, in_string);      stack_read(&myenv, in_string);
635      printf("okidok\n ");      printf("okidok\n ");
636    }    }
637    
638    exit(EXIT_SUCCESS);    exit(EXIT_SUCCESS);
639  }  }
   
 /* Local Variables: */  
 /* compile-command:"make CFLAGS=\"-Wall -g -rdynamic -ldl\" stack" */  
 /* End: */  
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