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

/* First, define some types. */

/* A value of some type */
typedef struct {
  enum {
    integer,
    string,
    func,                       /* Function pointer */
    symb, 
    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 */

  int refcount;                 /* Reference counter */

} value;

/* A symbol with a name and possible value */
/* (These do not need reference counters, they are kept unique by
   hashing.) */
typedef struct symbol_struct {
  char *id;                     /* Symbol name */
  value *val;                   /* The value (if any) bound to it */
  struct symbol_struct *next;   /* In case of hashing conflicts, a */
} symbol;                       /* symbol is a kind of stack item. */

/* A type for a hash table for symbols */
typedef symbol *hashtbl[HASHTBLSIZE]; /* Hash table declaration */

/* An item (value) on a stack */
typedef struct stackitem_struct
{
  value *item;                  /* The value on the stack */
  struct stackitem_struct *next; /* Next item */
} stackitem;

/* An environment; gives access to the stack and a hash table of
   defined symbols */
typedef struct {
  stackitem *head;              /* Head of the stack */
  hashtbl symbols;              /* Hash table of all variable bindings */
  int err;                      /* Error flag */
} environment;

/* A type for pointers to external functions */
typedef void (*funcp)(environment *); /* funcp is a pointer to a void
                                         function (environment *) */

/* Initialize a newly created environment */
void init_env(environment *env)
{
  long i;

  env->err=0;
  for(i= 0; i<HASHTBLSIZE; i++)
    env->symbols[i]= NULL;
}

/* Returns a pointer to a pointer to an element in the hash table. */
symbol **hash(hashtbl in_hashtbl, const char *in_string)
{
  long i= 0;
  unsigned long out_hash= 0;
  char key= '\0';
  symbol **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. */
void push(stackitem** stack_head, stackitem* in_item)
{
  in_item->next= *stack_head;
  *stack_head= in_item;
}

/* Push a value onto the stack */
void push_val(stackitem **stack_head, value *val)
{
  stackitem *new_item= malloc(sizeof(stackitem));
  new_item->item= val;
  val->refcount++;
  push(stack_head, new_item);
}

/* Push an integer onto the stack. */
void push_int(stackitem **stack_head, int in_val) 
{
  value *new_value= malloc(sizeof(value));
  stackitem *new_item= malloc(sizeof(stackitem));
  new_item->item= new_value;
  
  new_value->content.val= in_val;
  new_value->type= integer;
  new_value->refcount=1;

  push(stack_head, new_item);
}

/* Copy a string onto the stack. */
void push_cstring(stackitem **stack_head, const char *in_string)
{
  value *new_value= malloc(sizeof(value));
  stackitem *new_item= malloc(sizeof(stackitem));
  new_item->item=new_value;

  new_value->content.ptr= malloc(strlen(in_string)+1);
  strcpy(new_value->content.ptr, in_string);
  new_value->type= string;
  new_value->refcount=1;

  push(stack_head, new_item);
}

/* Push a symbol onto the stack. */
void push_sym(environment *env, const char *in_string)
{
  stackitem *new_item;          /* The new stack item */
  /* ...which will contain... */
  value *new_value;             /* A new symbol value */
  /* ...which might point to... */
  symbol **new_symbol;          /* (if needed) A new actual symbol */
  /* ...which, if possible, will be bound to... */
  value *new_fvalue;            /* (if needed) A new function value */
  /* ...which will point to... */
  void *funcptr;                /* A function pointer */

  static void *handle= NULL;    /* Dynamic linker handle */

  /* Create a new stack item containing a new value */
  new_item= malloc(sizeof(stackitem));
  new_value= malloc(sizeof(value));
  new_item->item=new_value;

  /* The new value is a symbol */
  new_value->type= symb;
  new_value->refcount= 1;

  /* Look up the symbol name in the hash table */
  new_symbol= hash(env->symbols, in_string);
  new_value->content.ptr= *new_symbol;

  if(*new_symbol==NULL) { /* If symbol was undefined */

    /* Create a new symbol */
    (*new_symbol)= malloc(sizeof(symbol));
    (*new_symbol)->val= NULL;   /* undefined value */
    (*new_symbol)->next= NULL;
    (*new_symbol)->id= malloc(strlen(in_string)+1);
    strcpy((*new_symbol)->id, in_string);

    /* Intern the new symbol in the hash table */
    new_value->content.ptr= *new_symbol;

    /* Try to load the symbol name as an external function, to see if
       we should bind the symbol to a new function pointer value */
    if(handle==NULL)            /* If no handle */
      handle= dlopen(NULL, RTLD_LAZY);

    funcptr= dlsym(handle, in_string); /* Get function pointer */
    if(dlerror()==NULL) {       /* If a function was found */
      new_fvalue= malloc(sizeof(value)); /* Create a new value */
      new_fvalue->type=func;    /* The new value is a function pointer */
      new_fvalue->content.ptr=funcptr; /* Store function pointer */
      (*new_symbol)->val= new_fvalue; /* Bind the symbol to the new
                                         function value */
      new_fvalue->refcount= 1;
    }
  }
  push(&(env->head), new_item);
}

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

/* Throw away a value */
void free_val(value *val){
  stackitem *item, *temp;

  val->refcount--;              /* Decrease the reference count */
  if(val->refcount == 0){
    switch (val->type){         /* and free the contents if necessary */
    case string:
      free(val->content.ptr);
      break;
    case list:                  /* lists needs to be freed recursively */
      item=val->content.ptr;
      while(item != NULL) {     /* for all stack items */
        free_val(item->item);   /* free the value */
        temp=item->next;        /* save next ptr */
        free(item);             /* free the stackitem */
        item=temp;              /* go to next stackitem */
      }
      free(val);                /* Free the actual list value */
      break;
    default:
      break;
    }
  }
}

/* Discard the top element of the stack. */
extern void toss(environment *env)
{
  stackitem *temp= env->head;

  if((env->head)==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }
  
  free_val(env->head->item);    /* Free the value */
  env->head= env->head->next;   /* Remove the top stack item */
  free(temp);                   /* Free the old top stack item */
}

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

/* Gets the type of a value */
extern void type(environment *env){
  int typenum;

  if((env->head)==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }
  typenum=env->head->item->type;
  toss(env);
  switch(typenum){
  case integer:
    push_sym(env, "integer");
    break;
  case string:
    push_sym(env, "string");
    break;
  case symb:
    push_sym(env, "symbol");
    break;
  case func:
    push_sym(env, "function");
    break;
  case list:
    push_sym(env, "list");
    break;
  default:
    push_sym(env, "unknown");
    break;
  }
}    

/* Prints the top element of the stack. */
void print_h(stackitem *stack_head)
{
  switch(stack_head->item->type) {
  case integer:
    printf("%d", stack_head->item->content.val);
    break;
  case string:
    printf("\"%s\"", (char*)stack_head->item->content.ptr);
    break;
  case symb:
    printf("'%s'", ((symbol *)(stack_head->item->content.ptr))->id);
    break;
  case func:
    printf("#<function %p>", (funcp)(stack_head->item->content.ptr));
    break;
  case list:
    printf("#<list %p>", (funcp)(stack_head->item->content.ptr));
    break;
  default:
    printf("#<unknown %p>", (funcp)(stack_head->item->content.ptr));
    break;
  }
}

extern void print_(environment *env) {
  if(env->head==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }
  print_h(env->head);
}

/* Prints the top element of the stack and then discards it. */
extern void print(environment *env)
{
  print_(env);
  if(env->err) return;
  toss(env);
}

/* 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_h(stack_head);
  nl();
}


/* Prints the stack. */
extern void printstack(environment *env)
{
  if(env->head == NULL) {
    return;
  }
  print_st(env->head, 1);
  nl();
}

/* Swap the two top elements on the stack. */
extern void swap(environment *env)
{
  stackitem *temp= env->head;
  
  if((env->head)==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }

  if(env->head->next==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }

  env->head= env->head->next;
  temp->next= env->head->next;
  env->head->next= temp;
} 

stackitem* copy(stackitem* in_item)
{
  stackitem *out_item= malloc(sizeof(stackitem));

  memcpy(out_item, in_item, sizeof(stackitem));
  out_item->next= NULL;

  return out_item;
}

/* Recall a value from a symbol, if bound */
extern void rcl(environment *env)
{
  value *val;

  if(env->head == NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }

  if(env->head->item->type!=symb) {
    printerr("Bad Argument Type");
    env->err=2;
    return;
  }

  val=((symbol *)(env->head->item->content.ptr))->val;
  if(val == NULL){
    printerr("Unbound Variable");
    env->err=3;
    return;
  }
  toss(env);            /* toss the symbol */
  if(env->err) return;
  push_val(&(env->head), val); /* Return its bound value */
}

/* If the top element is a symbol, determine if it's bound to a
   function value, and if it is, toss the symbol and execute the
   function. */
extern void eval(environment *env)
{
  funcp in_func;
  if(env->head==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }

  /* if it's a symbol */
  if(env->head->item->type==symb) {

    rcl(env);                   /* get its contents */
    if(env->err) return;
    if(env->head->item->type!=symb){ /* don't recurse symbols */
      eval(env);                        /* evaluate the value */
      return;
    }
  }

  /* If it's a lone function value, run it */
  if(env->head->item->type==func) {
    in_func= (funcp)(env->head->item->content.ptr);
    toss(env); 
    if(env->err) return;
    (*in_func)(env);
  }
}

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

  delimiter= env->head->item->content.ptr; /* Get delimiter */
  toss(env);

  iterator= env->head;

  if(iterator==NULL || iterator->item->content.ptr==delimiter) {
    temp= NULL;
    toss(env);
  } else {
    /* Search for first delimiter */
    while(iterator->next!=NULL
          && iterator->next->item->content.ptr!=delimiter)
      iterator= iterator->next;
    
    /* Extract list */
    temp= env->head;
    env->head= iterator->next;
    iterator->next= NULL;
    
    if(env->head!=NULL)
      toss(env);
  }

  /* Push list */
  pack= malloc(sizeof(value));
  pack->type= list;
  pack->content.ptr= temp;
  pack->refcount= 1;

  temp= malloc(sizeof(stackitem));
  temp->item= pack;

  push(&(env->head), temp);
}

/* Parse input. */
void stack_read(environment *env, 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(&(env->head), temp);
      break;
    }
    /* If integer */
    if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
      push_int(&(env->head), itemp);
      break;
    }
    /* Escape ';' with '\' */
    if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
      temp[1]= '\0';
      push_sym(env, temp);
      break;
    } 
    /* If symbol */
    if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
        push_sym(env, temp);
        break;
    }
    /* If single char */
    if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
      if(*temp==';') {
        if(!non_eval_flag) {
          eval(env);            /* Evaluate top element */
          break;
        }
        
        push_sym(env, ";");
        break;
      }

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

      if(*temp=='[') {
        push_sym(env, "[");
        non_eval_flag++;
        break;
      }
    }
  } while(0);

  free(temp);

  if(convert<2) {
    free(rest);
    return;
  }
   
  stack_read(env, rest);
  
  free(rest);
}

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

  /* Is top element a list? */
  if(env->head==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }
  if(env->head->item->type!=list) {
    printerr("Bad Argument Type");
    env->err=2;
    return;
  }

  /* The first list element is the new stack head */
  new_head= temp= env->head->item->content.ptr;

  env->head->item->refcount++;
  toss(env);

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

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

}

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

  if((env->head)==NULL || env->head->next==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }

  left= env->head->item->content.ptr;
  swap(env);
  right= env->head->item->content.ptr;
  result= (left==right);
  
  toss(env); toss(env);
  push_int(&(env->head), result);
}

/* Negates the top element on the stack. */
extern void not(environment *env)
{
  int val;

  if((env->head)==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }

  if(env->head->item->type!=integer) {
    printerr("Bad Argument Type");
    env->err=2;
    return;
  }

  val= env->head->item->content.val;
  toss(env);
  push_int(&(env->head), !val);
}

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

/* Give a symbol some content. */
extern void def(environment *env)
{
  symbol *sym;

  /* Needs two values on the stack, the top one must be a symbol */
  if(env->head==NULL || env->head->next==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }

  if(env->head->item->type!=symb) {
    printerr("Bad Argument Type");
    env->err=2;
    return;
  }

  /* long names are a pain */
  sym=env->head->item->content.ptr;

  /* if the symbol was bound to something else, throw it away */
  if(sym->val != NULL)
    free_val(sym->val);

  /* Bind the symbol to the value */
  sym->val= env->head->next->item;
  sym->val->refcount++;         /* Increase the reference counter */

  toss(env); toss(env);
} 

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

/* Clear stack */
extern void clear(environment *env)
{
  while(env->head!=NULL)
    toss(env);
}

/* List all defined words */
extern void words(environment *env)
{
  symbol *temp;
  int i;
  
  for(i= 0; i<HASHTBLSIZE; i++) {
    temp= env->symbols[i];
    while(temp!=NULL) {
      printf("%s\n", temp->id);
      temp= temp->next;
    }
  }
}

/* Forgets a symbol (remove it from the hash table) */
extern void forget(environment *env)
{
  char* sym_id;
  stackitem *stack_head= env->head;
  symbol **hash_entry, *temp;

  if(stack_head==NULL) {
    printerr("Too Few Arguments");
    env->err=1;
    return;
  }
  
  if(stack_head->item->type!=symb) {
    printerr("Bad Argument Type");
    env->err=2;
    return;
  }

  sym_id= ((symbol*)(stack_head->item->content.ptr))->id;
  toss(env);

  hash_entry= hash(env->symbols, sym_id);
  temp= *hash_entry;
  *hash_entry= (*hash_entry)->next;
  
  if(temp->val!=NULL) {
    free_val(temp->val);
  }
  free(temp->id);
  free(temp);
}

/* Returns the current error number to the stack */
extern void errn(environment *env){
  push_int(&(env->head), env->err);
}

int main()
{
  environment myenv;
  char in_string[100];

  init_env(&myenv);

  printf("okidok\n ");

  while(fgets(in_string, 100, stdin) != NULL) {
    stack_read(&myenv, in_string);
    if(myenv.err) {
      printf("(error %d) ", myenv.err);
      myenv.err=0;
    }
    printf("okidok\n ");
  }

  exit(EXIT_SUCCESS);
}
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	/* First, define some types. */
15
16	/* A value of some type */
17	typedef struct {
18	enum {
19	integer,
20	string,
21	func, /* Function pointer */
22	symb,
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	int refcount; /* Reference counter */
32
33	} value;
34
35	/* A symbol with a name and possible value */
36	/* (These do not need reference counters, they are kept unique by
37	hashing.) */
38	typedef struct symbol_struct {
39	char id; / Symbol name */
40	value val; / The value (if any) bound to it */
41	struct symbol_struct next; / In case of hashing conflicts, a */
42	} symbol; /* symbol is a kind of stack item. */
43
44	/* A type for a hash table for symbols */
45	typedef symbol hashtbl[HASHTBLSIZE]; / Hash table declaration */
46
47	/* An item (value) on a stack */
48	typedef struct stackitem_struct
49	{
50	value item; / The value on the stack */
51	struct stackitem_struct next; / Next item */
52	} stackitem;
53
54	/* An environment; gives access to the stack and a hash table of
55	defined symbols */
56	typedef struct {
57	stackitem head; / Head of the stack */
58	hashtbl symbols; /* Hash table of all variable bindings */
59	int err; /* Error flag */
60	} environment;
61
62	/* A type for pointers to external functions */
63	typedef void (funcp)(environment ); /* funcp is a pointer to a void
64	function (environment ) /
65
66	/* Initialize a newly created environment */
67	void init_env(environment *env)
68	{
69	long i;
70
71	env->err=0;
72	for(i= 0; i<HASHTBLSIZE; i++)
73	env->symbols[i]= NULL;
74	}
75
76	/* Returns a pointer to a pointer to an element in the hash table. */
77	symbol *hash(hashtbl in_hashtbl, const char in_string)
78	{
79	long i= 0;
80	unsigned long out_hash= 0;
81	char key= '\0';
82	symbol **position;
83
84	while(1){ /* Hash in_string */
85	key= in_string[i++];
86	if(key=='\0')
87	break;
88	out_hash= out_hash*32+key;
89	}
90
91	out_hash= out_hash%HASHTBLSIZE;
92	position= &(in_hashtbl[out_hash]);
93
94	while(1){
95	if(position==NULL) / If empty */
96	return position;
97
98	if(strcmp(in_string, (position)->id)==0) / If match */
99	return position;
100
101	position= &((position)->next); / Try next */
102	}
103	}
104
105	/* Generic push function. */
106	void push(stackitem** stack_head, stackitem* in_item)
107	{
108	in_item->next= *stack_head;
109	*stack_head= in_item;
110	}
111
112	/* Push a value onto the stack */
113	void push_val(stackitem *stack_head, value val)
114	{
115	stackitem *new_item= malloc(sizeof(stackitem));
116	new_item->item= val;
117	val->refcount++;
118	push(stack_head, new_item);
119	}
120
121	/* Push an integer onto the stack. */
122	void push_int(stackitem **stack_head, int in_val)
123	{
124	value *new_value= malloc(sizeof(value));
125	stackitem *new_item= malloc(sizeof(stackitem));
126	new_item->item= new_value;
127
128	new_value->content.val= in_val;
129	new_value->type= integer;
130	new_value->refcount=1;
131
132	push(stack_head, new_item);
133	}
134
135	/* Copy a string onto the stack. */
136	void push_cstring(stackitem *stack_head, const char in_string)
137	{
138	value *new_value= malloc(sizeof(value));
139	stackitem *new_item= malloc(sizeof(stackitem));
140	new_item->item=new_value;
141
142	new_value->content.ptr= malloc(strlen(in_string)+1);
143	strcpy(new_value->content.ptr, in_string);
144	new_value->type= string;
145	new_value->refcount=1;
146
147	push(stack_head, new_item);
148	}
149
150	/* Push a symbol onto the stack. */
151	void push_sym(environment env, const char in_string)
152	{
153	stackitem new_item; / The new stack item */
154	/* ...which will contain... */
155	value new_value; / A new symbol value */
156	/* ...which might point to... */
157	symbol *new_symbol; / (if needed) A new actual symbol */
158	/* ...which, if possible, will be bound to... */
159	value new_fvalue; / (if needed) A new function value */
160	/* ...which will point to... */
161	void funcptr; / A function pointer */
162
163	static void handle= NULL; / Dynamic linker handle */
164
165	/* Create a new stack item containing a new value */
166	new_item= malloc(sizeof(stackitem));
167	new_value= malloc(sizeof(value));
168	new_item->item=new_value;
169
170	/* The new value is a symbol */
171	new_value->type= symb;
172	new_value->refcount= 1;
173
174	/* Look up the symbol name in the hash table */
175	new_symbol= hash(env->symbols, in_string);
176	new_value->content.ptr= *new_symbol;
177
178	if(new_symbol==NULL) { / If symbol was undefined */
179
180	/* Create a new symbol */
181	(*new_symbol)= malloc(sizeof(symbol));
182	(new_symbol)->val= NULL; / undefined value */
183	(*new_symbol)->next= NULL;
184	(*new_symbol)->id= malloc(strlen(in_string)+1);
185	strcpy((*new_symbol)->id, in_string);
186
187	/* Intern the new symbol in the hash table */
188	new_value->content.ptr= *new_symbol;
189
190	/* Try to load the symbol name as an external function, to see if
191	we should bind the symbol to a new function pointer value */
192	if(handle==NULL) /* If no handle */
193	handle= dlopen(NULL, RTLD_LAZY);
194
195	funcptr= dlsym(handle, in_string); /* Get function pointer */
196	if(dlerror()==NULL) { /* If a function was found */
197	new_fvalue= malloc(sizeof(value)); /* Create a new value */
198	new_fvalue->type=func; /* The new value is a function pointer */
199	new_fvalue->content.ptr=funcptr; /* Store function pointer */
200	(new_symbol)->val= new_fvalue; / Bind the symbol to the new
201	function value */
202	new_fvalue->refcount= 1;
203	}
204	}
205	push(&(env->head), new_item);
206	}
207
208	void printerr(const char* in_string) {
209	fprintf(stderr, "Err: %s\n", in_string);
210	}
211
212	/* Throw away a value */
213	void free_val(value *val){
214	stackitem item, temp;
215
216	val->refcount--; /* Decrease the reference count */
217	if(val->refcount == 0){
218	switch (val->type){ /* and free the contents if necessary */
219	case string:
220	free(val->content.ptr);
221	break;
222	case list: /* lists needs to be freed recursively */
223	item=val->content.ptr;
224	while(item != NULL) { /* for all stack items */
225	free_val(item->item); /* free the value */
226	temp=item->next; /* save next ptr */
227	free(item); /* free the stackitem */
228	item=temp; /* go to next stackitem */
229	}
230	free(val); /* Free the actual list value */
231	break;
232	default:
233	break;
234	}
235	}
236	}
237
238	/* Discard the top element of the stack. */
239	extern void toss(environment *env)
240	{
241	stackitem *temp= env->head;
242
243	if((env->head)==NULL) {
244	printerr("Too Few Arguments");
245	env->err=1;
246	return;
247	}
248
249	free_val(env->head->item); /* Free the value */
250	env->head= env->head->next; /* Remove the top stack item */
251	free(temp); /* Free the old top stack item */
252	}
253
254	/* Print newline. */
255	extern void nl()
256	{
257	printf("\n");
258	}
259
260	/* Gets the type of a value */
261	extern void type(environment *env){
262	int typenum;
263
264	if((env->head)==NULL) {
265	printerr("Too Few Arguments");
266	env->err=1;
267	return;
268	}
269	typenum=env->head->item->type;
270	toss(env);
271	switch(typenum){
272	case integer:
273	push_sym(env, "integer");
274	break;
275	case string:
276	push_sym(env, "string");
277	break;
278	case symb:
279	push_sym(env, "symbol");
280	break;
281	case func:
282	push_sym(env, "function");
283	break;
284	case list:
285	push_sym(env, "list");
286	break;
287	default:
288	push_sym(env, "unknown");
289	break;
290	}
291	}
292
293	/* Prints the top element of the stack. */
294	void print_h(stackitem *stack_head)
295	{
296	switch(stack_head->item->type) {
297	case integer:
298	printf("%d", stack_head->item->content.val);
299	break;
300	case string:
301	printf("\"%s\"", (char*)stack_head->item->content.ptr);
302	break;
303	case symb:
304	printf("'%s'", ((symbol *)(stack_head->item->content.ptr))->id);
305	break;
306	case func:
307	printf("#<function %p>", (funcp)(stack_head->item->content.ptr));
308	break;
309	case list:
310	printf("#<list %p>", (funcp)(stack_head->item->content.ptr));
311	break;
312	default:
313	printf("#<unknown %p>", (funcp)(stack_head->item->content.ptr));
314	break;
315	}
316	}
317
318	extern void print_(environment *env) {
319	if(env->head==NULL) {
320	printerr("Too Few Arguments");
321	env->err=1;
322	return;
323	}
324	print_h(env->head);
325	}
326
327	/* Prints the top element of the stack and then discards it. */
328	extern void print(environment *env)
329	{
330	print_(env);
331	if(env->err) return;
332	toss(env);
333	}
334
335	/* Only to be called by function printstack. */
336	void print_st(stackitem *stack_head, long counter)
337	{
338	if(stack_head->next != NULL)
339	print_st(stack_head->next, counter+1);
340	printf("%ld: ", counter);
341	print_h(stack_head);
342	nl();
343	}
344
345
346
347	/* Prints the stack. */
348	extern void printstack(environment *env)
349	{
350	if(env->head == NULL) {
351	return;
352	}
353	print_st(env->head, 1);
354	nl();
355	}
356
357	/* Swap the two top elements on the stack. */
358	extern void swap(environment *env)
359	{
360	stackitem *temp= env->head;
361
362	if((env->head)==NULL) {
363	printerr("Too Few Arguments");
364	env->err=1;
365	return;
366	}
367
368	if(env->head->next==NULL) {
369	printerr("Too Few Arguments");
370	env->err=1;
371	return;
372	}
373
374	env->head= env->head->next;
375	temp->next= env->head->next;
376	env->head->next= temp;
377	}
378
379	stackitem* copy(stackitem* in_item)
380	{
381	stackitem *out_item= malloc(sizeof(stackitem));
382
383	memcpy(out_item, in_item, sizeof(stackitem));
384	out_item->next= NULL;
385
386	return out_item;
387	}
388
389	/* Recall a value from a symbol, if bound */
390	extern void rcl(environment *env)
391	{
392	value *val;
393
394	if(env->head == NULL) {
395	printerr("Too Few Arguments");
396	env->err=1;
397	return;
398	}
399
400	if(env->head->item->type!=symb) {
401	printerr("Bad Argument Type");
402	env->err=2;
403	return;
404	}
405
406	val=((symbol *)(env->head->item->content.ptr))->val;
407	if(val == NULL){
408	printerr("Unbound Variable");
409	env->err=3;
410	return;
411	}
412	toss(env); /* toss the symbol */
413	if(env->err) return;
414	push_val(&(env->head), val); /* Return its bound value */
415	}
416
417	/* If the top element is a symbol, determine if it's bound to a
418	function value, and if it is, toss the symbol and execute the
419	function. */
420	extern void eval(environment *env)
421	{
422	funcp in_func;
423	if(env->head==NULL) {
424	printerr("Too Few Arguments");
425	env->err=1;
426	return;
427	}
428
429	/* if it's a symbol */
430	if(env->head->item->type==symb) {
431
432	rcl(env); /* get its contents */
433	if(env->err) return;
434	if(env->head->item->type!=symb){ /* don't recurse symbols */
435	eval(env); /* evaluate the value */
436	return;
437	}
438	}
439
440	/* If it's a lone function value, run it */
441	if(env->head->item->type==func) {
442	in_func= (funcp)(env->head->item->content.ptr);
443	toss(env);
444	if(env->err) return;
445	(*in_func)(env);
446	}
447	}
448
449	/* Make a list. */
450	extern void pack(environment *env)
451	{
452	void* delimiter;
453	stackitem iterator, temp;
454	value *pack;
455
456	delimiter= env->head->item->content.ptr; /* Get delimiter */
457	toss(env);
458
459	iterator= env->head;
460
461	if(iterator==NULL \|\| iterator->item->content.ptr==delimiter) {
462	temp= NULL;
463	toss(env);
464	} else {
465	/* Search for first delimiter */
466	while(iterator->next!=NULL
467	&& iterator->next->item->content.ptr!=delimiter)
468	iterator= iterator->next;
469
470	/* Extract list */
471	temp= env->head;
472	env->head= iterator->next;
473	iterator->next= NULL;
474
475	if(env->head!=NULL)
476	toss(env);
477	}
478
479	/* Push list */
480	pack= malloc(sizeof(value));
481	pack->type= list;
482	pack->content.ptr= temp;
483	pack->refcount= 1;
484
485	temp= malloc(sizeof(stackitem));
486	temp->item= pack;
487
488	push(&(env->head), temp);
489	}
490
491	/* Parse input. */
492	void stack_read(environment env, char in_line)
493	{
494	char temp, rest;
495	int itemp;
496	size_t inlength= strlen(in_line)+1;
497	int convert= 0;
498	static int non_eval_flag= 0;
499
500	temp= malloc(inlength);
501	rest= malloc(inlength);
502
503	do {
504	/* If string */
505	if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
506	push_cstring(&(env->head), temp);
507	break;
508	}
509	/* If integer */
510	if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
511	push_int(&(env->head), itemp);
512	break;
513	}
514	/* Escape ';' with '\' */
515	if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
516	temp[1]= '\0';
517	push_sym(env, temp);
518	break;
519	}
520	/* If symbol */
521	if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
522	push_sym(env, temp);
523	break;
524	}
525	/* If single char */
526	if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
527	if(*temp==';') {
528	if(!non_eval_flag) {
529	eval(env); /* Evaluate top element */
530	break;
531	}
532
533	push_sym(env, ";");
534	break;
535	}
536
537	if(*temp==']') {
538	push_sym(env, "[");
539	pack(env);
540	if(non_eval_flag!=0)
541	non_eval_flag--;
542	break;
543	}
544
545	if(*temp=='[') {
546	push_sym(env, "[");
547	non_eval_flag++;
548	break;
549	}
550	}
551	} while(0);
552
553	free(temp);
554
555	if(convert<2) {
556	free(rest);
557	return;
558	}
559
560	stack_read(env, rest);
561
562	free(rest);
563	}
564
565	/* Relocate elements of the list on the stack. */
566	extern void expand(environment *env)
567	{
568	stackitem temp, new_head;
569
570	/* Is top element a list? */
571	if(env->head==NULL) {
572	printerr("Too Few Arguments");
573	env->err=1;
574	return;
575	}
576	if(env->head->item->type!=list) {
577	printerr("Bad Argument Type");
578	env->err=2;
579	return;
580	}
581
582	/* The first list element is the new stack head */
583	new_head= temp= env->head->item->content.ptr;
584
585	env->head->item->refcount++;
586	toss(env);
587
588	/* Find the end of the list */
589	while(temp->next!=NULL)
590	temp= temp->next;
591
592	/* Connect the tail of the list with the old stack head */
593	temp->next= env->head;
594	env->head= new_head; /* ...and voila! */
595
596	}
597
598	/* Compares two elements by reference. */
599	extern void eq(environment *env)
600	{
601	void left, right;
602	int result;
603
604	if((env->head)==NULL \|\| env->head->next==NULL) {
605	printerr("Too Few Arguments");
606	env->err=1;
607	return;
608	}
609
610	left= env->head->item->content.ptr;
611	swap(env);
612	right= env->head->item->content.ptr;
613	result= (left==right);
614
615	toss(env); toss(env);
616	push_int(&(env->head), result);
617	}
618
619	/* Negates the top element on the stack. */
620	extern void not(environment *env)
621	{
622	int val;
623
624	if((env->head)==NULL) {
625	printerr("Too Few Arguments");
626	env->err=1;
627	return;
628	}
629
630	if(env->head->item->type!=integer) {
631	printerr("Bad Argument Type");
632	env->err=2;
633	return;
634	}
635
636	val= env->head->item->content.val;
637	toss(env);
638	push_int(&(env->head), !val);
639	}
640
641	/* Compares the two top elements on the stack and return 0 if they're the
642	same. */
643	extern void neq(environment *env)
644	{
645	eq(env);
646	not(env);
647	}
648
649	/* Give a symbol some content. */
650	extern void def(environment *env)
651	{
652	symbol *sym;
653
654	/* Needs two values on the stack, the top one must be a symbol */
655	if(env->head==NULL \|\| env->head->next==NULL) {
656	printerr("Too Few Arguments");
657	env->err=1;
658	return;
659	}
660
661	if(env->head->item->type!=symb) {
662	printerr("Bad Argument Type");
663	env->err=2;
664	return;
665	}
666
667	/* long names are a pain */
668	sym=env->head->item->content.ptr;
669
670	/* if the symbol was bound to something else, throw it away */
671	if(sym->val != NULL)
672	free_val(sym->val);
673
674	/* Bind the symbol to the value */
675	sym->val= env->head->next->item;
676	sym->val->refcount++; /* Increase the reference counter */
677
678	toss(env); toss(env);
679	}
680
681	/* Quit stack. */
682	extern void quit(environment *env)
683	{
684	exit(EXIT_SUCCESS);
685	}
686
687	/* Clear stack */
688	extern void clear(environment *env)
689	{
690	while(env->head!=NULL)
691	toss(env);
692	}
693
694	/* List all defined words */
695	extern void words(environment *env)
696	{
697	symbol *temp;
698	int i;
699
700	for(i= 0; i<HASHTBLSIZE; i++) {
701	temp= env->symbols[i];
702	while(temp!=NULL) {
703	printf("%s\n", temp->id);
704	temp= temp->next;
705	}
706	}
707	}
708
709	/* Forgets a symbol (remove it from the hash table) */
710	extern void forget(environment *env)
711	{
712	char* sym_id;
713	stackitem *stack_head= env->head;
714	symbol *hash_entry, temp;
715
716	if(stack_head==NULL) {
717	printerr("Too Few Arguments");
718	env->err=1;
719	return;
720	}
721
722	if(stack_head->item->type!=symb) {
723	printerr("Bad Argument Type");
724	env->err=2;
725	return;
726	}
727
728	sym_id= ((symbol*)(stack_head->item->content.ptr))->id;
729	toss(env);
730
731	hash_entry= hash(env->symbols, sym_id);
732	temp= *hash_entry;
733	hash_entry= (hash_entry)->next;
734
735	if(temp->val!=NULL) {
736	free_val(temp->val);
737	}
738	free(temp->id);
739	free(temp);
740	}
741
742	/* Returns the current error number to the stack */
743	extern void errn(environment *env){
744	push_int(&(env->head), env->err);
745	}
746
747	int main()
748	{
749	environment myenv;
750	char in_string[100];
751
752	init_env(&myenv);
753
754	printf("okidok\n ");
755
756	while(fgets(in_string, 100, stdin) != NULL) {
757	stack_read(&myenv, in_string);
758	if(myenv.err) {
759	printf("(error %d) ", myenv.err);
760	myenv.err=0;
761	}
762	printf("okidok\n ");
763	}
764
765	exit(EXIT_SUCCESS);
766	}