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 */
  int non_eval_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)
{
  int i;

  env->err= 0;
  env->non_eval_flag= 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)
{
  int i= 0;
  unsigned int 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:
    /* A list is just a stack, so make stack_head point to it */
    stack_head=(stackitem *)(stack_head->item->content.ptr);
    printf("[ ");
    while(stack_head != NULL) {
      print_h(stack_head);
      printf(" ");
      stack_head=stack_head->next;
    }
    printf("]");
    break;
  default:
    printf("#<unknown %p>", (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 || 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;
} 

/* 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 */
}

extern void pack(environment*);
void stack_read(environment*, char*);


/* 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;
  value* temp_val;
  stackitem* iterator;

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

  switch(env->head->item->type) {
    /* if it's a symbol */
  case 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;
    }
    break;

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

    /* If it's a list */
  case list:
    temp_val= env->head->item;
    env->head->item->refcount++;
    toss(env);
    if(env->err) return;
    iterator= (stackitem*)temp_val->content.ptr;
    while(iterator!=NULL && iterator->item!=NULL) {
      push_val(&(env->head), iterator->item);
      if(env->head->item->type==symb
        && strcmp(";", ((symbol*)(env->head->item->content.ptr))->id)==0) {
        toss(env);
        if(env->err) return;
        eval(env);
        if(env->err) return;
      }
      iterator= iterator->next;
    }
    free_val(temp_val);
    break;

    /* If it's a string */
  case string:
    temp_val= env->head->item;
    env->head->item->refcount++;
    toss(env);
    if(env->err) return;
    push_sym(env, "[");
    env->non_eval_flag++;
    stack_read(env, (char*)temp_val->content.ptr);
    env->non_eval_flag--;
    push_sym(env, "["); pack(env);
    if(env->err) return;
    eval(env);
    if(env->err) return;
    free_val(temp_val);
    break;

  default:
  }
}

/* Reverse (flip) a list */
extern void rev(environment *env){
  stackitem *old_head, *new_head, *item;

  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;
  }

  old_head=(stackitem *)(env->head->item->content.ptr);
  new_head=NULL;
  while(old_head != NULL){
    item=old_head;
    old_head=old_head->next;
    item->next=new_head;
    new_head=item;
  }
  env->head->item->content.ptr=new_head;
}

/* 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);
  rev(env);
}

/* 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;

  temp= malloc(inlength);
  rest= malloc(inlength);

  do {
    /* If comment */
    if((convert= sscanf(in_line, "#%[^\n\r]", rest))) {
      free(temp); free(rest);
      return;
    }

    /* 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(!env->non_eval_flag) {
          eval(env);            /* Evaluate top element */
          break;
        }
        
        push_sym(env, ";");
        break;
      }

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

      if(*temp=='[') {
        push_sym(env, "[");
        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;
  }

  rev(env);

  if(env->err)
    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 ");
  }
  quit(&myenv);
  return EXIT_FAILURE;
}
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	int non_eval_flag;
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	int i;
71
72	env->err= 0;
73	env->non_eval_flag= 0;
74	for(i= 0; i<HASHTBLSIZE; i++)
75	env->symbols[i]= NULL;
76	}
77
78	/* Returns a pointer to a pointer to an element in the hash table. */
79	symbol *hash(hashtbl in_hashtbl, const char in_string)
80	{
81	int i= 0;
82	unsigned int out_hash= 0;
83	char key= '\0';
84	symbol **position;
85
86	while(1){ /* Hash in_string */
87	key= in_string[i++];
88	if(key=='\0')
89	break;
90	out_hash= out_hash*32+key;
91	}
92
93	out_hash= out_hash%HASHTBLSIZE;
94	position= &(in_hashtbl[out_hash]);
95
96	while(1){
97	if(position==NULL) / If empty */
98	return position;
99
100	if(strcmp(in_string, (position)->id)==0) / If match */
101	return position;
102
103	position= &((position)->next); / Try next */
104	}
105	}
106
107	/* Generic push function. */
108	void push(stackitem** stack_head, stackitem* in_item)
109	{
110	in_item->next= *stack_head;
111	*stack_head= in_item;
112	}
113
114	/* Push a value onto the stack */
115	void push_val(stackitem *stack_head, value val)
116	{
117	stackitem *new_item= malloc(sizeof(stackitem));
118	new_item->item= val;
119	val->refcount++;
120	push(stack_head, new_item);
121	}
122
123	/* Push an integer onto the stack. */
124	void push_int(stackitem **stack_head, int in_val)
125	{
126	value *new_value= malloc(sizeof(value));
127	stackitem *new_item= malloc(sizeof(stackitem));
128	new_item->item= new_value;
129
130	new_value->content.val= in_val;
131	new_value->type= integer;
132	new_value->refcount=1;
133
134	push(stack_head, new_item);
135	}
136
137	/* Copy a string onto the stack. */
138	void push_cstring(stackitem *stack_head, const char in_string)
139	{
140	value *new_value= malloc(sizeof(value));
141	stackitem *new_item= malloc(sizeof(stackitem));
142	new_item->item=new_value;
143
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	}
151
152	/* Push a symbol onto the stack. */
153	void push_sym(environment env, const char in_string)
154	{
155	stackitem new_item; / The new stack item */
156	/* ...which will contain... */
157	value new_value; / A new symbol value */
158	/* ...which might point to... */
159	symbol *new_symbol; / (if needed) A new actual symbol */
160	/* ...which, if possible, will be bound to... */
161	value new_fvalue; / (if needed) A new function value */
162	/* ...which will point to... */
163	void funcptr; / A function pointer */
164
165	static void handle= NULL; / Dynamic linker handle */
166
167	/* Create a new stack item containing a new value */
168	new_item= malloc(sizeof(stackitem));
169	new_value= malloc(sizeof(value));
170	new_item->item=new_value;
171
172	/* The new value is a symbol */
173	new_value->type= symb;
174	new_value->refcount= 1;
175
176	/* Look up the symbol name in the hash table */
177	new_symbol= hash(env->symbols, in_string);
178	new_value->content.ptr= *new_symbol;
179
180	if(new_symbol==NULL) { / If symbol was undefined */
181
182	/* Create a new symbol */
183	(*new_symbol)= malloc(sizeof(symbol));
184	(new_symbol)->val= NULL; / undefined value */
185	(*new_symbol)->next= NULL;
186	(*new_symbol)->id= malloc(strlen(in_string)+1);
187	strcpy((*new_symbol)->id, in_string);
188
189	/* Intern the new symbol in the hash table */
190	new_value->content.ptr= *new_symbol;
191
192	/* Try to load the symbol name as an external function, to see if
193	we should bind the symbol to a new function pointer value */
194	if(handle==NULL) /* If no handle */
195	handle= dlopen(NULL, RTLD_LAZY);
196
197	funcptr= dlsym(handle, in_string); /* Get function pointer */
198	if(dlerror()==NULL) { /* If a function was found */
199	new_fvalue= malloc(sizeof(value)); /* Create a new value */
200	new_fvalue->type=func; /* The new value is a function pointer */
201	new_fvalue->content.ptr=funcptr; /* Store function pointer */
202	(new_symbol)->val= new_fvalue; / Bind the symbol to the new
203	function value */
204	new_fvalue->refcount= 1;
205	}
206	}
207	push(&(env->head), new_item);
208	}
209
210	void printerr(const char* in_string) {
211	fprintf(stderr, "Err: %s\n", in_string);
212	}
213
214	/* Throw away a value */
215	void free_val(value *val){
216	stackitem item, temp;
217
218	val->refcount--; /* Decrease the reference count */
219	if(val->refcount == 0){
220	switch (val->type){ /* and free the contents if necessary */
221	case string:
222	free(val->content.ptr);
223	break;
224	case list: /* lists needs to be freed recursively */
225	item=val->content.ptr;
226	while(item != NULL) { /* for all stack items */
227	free_val(item->item); /* free the value */
228	temp=item->next; /* save next ptr */
229	free(item); /* free the stackitem */
230	item=temp; /* go to next stackitem */
231	}
232	free(val); /* Free the actual list value */
233	break;
234	default:
235	break;
236	}
237	}
238	}
239
240	/* Discard the top element of the stack. */
241	extern void toss(environment *env)
242	{
243	stackitem *temp= env->head;
244
245	if((env->head)==NULL) {
246	printerr("Too Few Arguments");
247	env->err=1;
248	return;
249	}
250
251	free_val(env->head->item); /* Free the value */
252	env->head= env->head->next; /* Remove the top stack item */
253	free(temp); /* Free the old top stack item */
254	}
255
256	/* Print newline. */
257	extern void nl()
258	{
259	printf("\n");
260	}
261
262	/* Gets the type of a value */
263	extern void type(environment *env){
264	int typenum;
265
266	if((env->head)==NULL) {
267	printerr("Too Few Arguments");
268	env->err=1;
269	return;
270	}
271	typenum=env->head->item->type;
272	toss(env);
273	switch(typenum){
274	case integer:
275	push_sym(env, "integer");
276	break;
277	case string:
278	push_sym(env, "string");
279	break;
280	case symb:
281	push_sym(env, "symbol");
282	break;
283	case func:
284	push_sym(env, "function");
285	break;
286	case list:
287	push_sym(env, "list");
288	break;
289	default:
290	push_sym(env, "unknown");
291	break;
292	}
293	}
294
295	/* Prints the top element of the stack. */
296	void print_h(stackitem *stack_head)
297	{
298	switch(stack_head->item->type) {
299	case integer:
300	printf("%d", stack_head->item->content.val);
301	break;
302	case string:
303	printf("\"%s\"", (char*)stack_head->item->content.ptr);
304	break;
305	case symb:
306	printf("%s", ((symbol *)(stack_head->item->content.ptr))->id);
307	break;
308	case func:
309	printf("#<function %p>", (funcp)(stack_head->item->content.ptr));
310	break;
311	case list:
312	/* A list is just a stack, so make stack_head point to it */
313	stack_head=(stackitem *)(stack_head->item->content.ptr);
314	printf("[ ");
315	while(stack_head != NULL) {
316	print_h(stack_head);
317	printf(" ");
318	stack_head=stack_head->next;
319	}
320	printf("]");
321	break;
322	default:
323	printf("#<unknown %p>", (stack_head->item->content.ptr));
324	break;
325	}
326	}
327
328	extern void print_(environment *env) {
329	if(env->head==NULL) {
330	printerr("Too Few Arguments");
331	env->err=1;
332	return;
333	}
334	print_h(env->head);
335	}
336
337	/* Prints the top element of the stack and then discards it. */
338	extern void print(environment *env)
339	{
340	print_(env);
341	if(env->err) return;
342	toss(env);
343	}
344
345	/* Only to be called by function printstack. */
346	void print_st(stackitem *stack_head, long counter)
347	{
348	if(stack_head->next != NULL)
349	print_st(stack_head->next, counter+1);
350	printf("%ld: ", counter);
351	print_h(stack_head);
352	nl();
353	}
354
355	/* Prints the stack. */
356	extern void printstack(environment *env)
357	{
358	if(env->head == NULL) {
359	return;
360	}
361	print_st(env->head, 1);
362	nl();
363	}
364
365	/* Swap the two top elements on the stack. */
366	extern void swap(environment *env)
367	{
368	stackitem *temp= env->head;
369
370	if(env->head==NULL \|\| env->head->next==NULL) {
371	printerr("Too Few Arguments");
372	env->err=1;
373	return;
374	}
375
376	env->head= env->head->next;
377	temp->next= env->head->next;
378	env->head->next= temp;
379	}
380
381	/* Recall a value from a symbol, if bound */
382	extern void rcl(environment *env)
383	{
384	value *val;
385
386	if(env->head == NULL) {
387	printerr("Too Few Arguments");
388	env->err=1;
389	return;
390	}
391
392	if(env->head->item->type!=symb) {
393	printerr("Bad Argument Type");
394	env->err=2;
395	return;
396	}
397
398	val=((symbol *)(env->head->item->content.ptr))->val;
399	if(val == NULL){
400	printerr("Unbound Variable");
401	env->err=3;
402	return;
403	}
404	toss(env); /* toss the symbol */
405	if(env->err) return;
406	push_val(&(env->head), val); /* Return its bound value */
407	}
408
409	extern void pack(environment*);
410	void stack_read(environment, char);
411
412
413	/* If the top element is a symbol, determine if it's bound to a
414	function value, and if it is, toss the symbol and execute the
415	function. */
416	extern void eval(environment *env)
417	{
418	funcp in_func;
419	value* temp_val;
420	stackitem* iterator;
421
422	if(env->head==NULL) {
423	printerr("Too Few Arguments");
424	env->err=1;
425	return;
426	}
427
428	switch(env->head->item->type) {
429	/* if it's a symbol */
430	case symb:
431	rcl(env); /* get its contents */
432	if(env->err) return;
433	if(env->head->item->type!=symb){ /* don't recurse symbols */
434	eval(env); /* evaluate the value */
435	return;
436	}
437	break;
438
439	/* If it's a lone function value, run it */
440	case func:
441	in_func= (funcp)(env->head->item->content.ptr);
442	toss(env);
443	if(env->err) return;
444	(*in_func)(env);
445	break;
446
447	/* If it's a list */
448	case list:
449	temp_val= env->head->item;
450	env->head->item->refcount++;
451	toss(env);
452	if(env->err) return;
453	iterator= (stackitem*)temp_val->content.ptr;
454	while(iterator!=NULL && iterator->item!=NULL) {
455	push_val(&(env->head), iterator->item);
456	if(env->head->item->type==symb
457	&& strcmp(";", ((symbol*)(env->head->item->content.ptr))->id)==0) {
458	toss(env);
459	if(env->err) return;
460	eval(env);
461	if(env->err) return;
462	}
463	iterator= iterator->next;
464	}
465	free_val(temp_val);
466	break;
467
468	/* If it's a string */
469	case string:
470	temp_val= env->head->item;
471	env->head->item->refcount++;
472	toss(env);
473	if(env->err) return;
474	push_sym(env, "[");
475	env->non_eval_flag++;
476	stack_read(env, (char*)temp_val->content.ptr);
477	env->non_eval_flag--;
478	push_sym(env, "["); pack(env);
479	if(env->err) return;
480	eval(env);
481	if(env->err) return;
482	free_val(temp_val);
483	break;
484
485	default:
486	}
487	}
488
489	/* Reverse (flip) a list */
490	extern void rev(environment *env){
491	stackitem old_head, new_head, *item;
492
493	if((env->head)==NULL) {
494	printerr("Too Few Arguments");
495	env->err=1;
496	return;
497	}
498
499	if(env->head->item->type!=list) {
500	printerr("Bad Argument Type");
501	env->err=2;
502	return;
503	}
504
505	old_head=(stackitem *)(env->head->item->content.ptr);
506	new_head=NULL;
507	while(old_head != NULL){
508	item=old_head;
509	old_head=old_head->next;
510	item->next=new_head;
511	new_head=item;
512	}
513	env->head->item->content.ptr=new_head;
514	}
515
516	/* Make a list. */
517	extern void pack(environment *env)
518	{
519	void* delimiter;
520	stackitem iterator, temp;
521	value *pack;
522
523	delimiter= env->head->item->content.ptr; /* Get delimiter */
524	toss(env);
525
526	iterator= env->head;
527
528	if(iterator==NULL \|\| iterator->item->content.ptr==delimiter) {
529	temp= NULL;
530	toss(env);
531	} else {
532	/* Search for first delimiter */
533	while(iterator->next!=NULL
534	&& iterator->next->item->content.ptr!=delimiter)
535	iterator= iterator->next;
536
537	/* Extract list */
538	temp= env->head;
539	env->head= iterator->next;
540	iterator->next= NULL;
541
542	if(env->head!=NULL)
543	toss(env);
544	}
545
546	/* Push list */
547	pack= malloc(sizeof(value));
548	pack->type= list;
549	pack->content.ptr= temp;
550	pack->refcount= 1;
551
552	temp= malloc(sizeof(stackitem));
553	temp->item= pack;
554
555	push(&(env->head), temp);
556	rev(env);
557	}
558
559	/* Parse input. */
560	void stack_read(environment env, char in_line)
561	{
562	char temp, rest;
563	int itemp;
564	size_t inlength= strlen(in_line)+1;
565	int convert= 0;
566
567	temp= malloc(inlength);
568	rest= malloc(inlength);
569
570	do {
571	/* If comment */
572	if((convert= sscanf(in_line, "#%[^\n\r]", rest))) {
573	free(temp); free(rest);
574	return;
575	}
576
577	/* If string */
578	if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
579	push_cstring(&(env->head), temp);
580	break;
581	}
582	/* If integer */
583	if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
584	push_int(&(env->head), itemp);
585	break;
586	}
587	/* Escape ';' with '\' */
588	if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
589	temp[1]= '\0';
590	push_sym(env, temp);
591	break;
592	}
593	/* If symbol */
594	if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
595	push_sym(env, temp);
596	break;
597	}
598	/* If single char */
599	if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
600	if(*temp==';') {
601	if(!env->non_eval_flag) {
602	eval(env); /* Evaluate top element */
603	break;
604	}
605
606	push_sym(env, ";");
607	break;
608	}
609
610	if(*temp==']') {
611	push_sym(env, "[");
612	pack(env);
613	if(env->non_eval_flag)
614	env->non_eval_flag--;
615	break;
616	}
617
618	if(*temp=='[') {
619	push_sym(env, "[");
620	env->non_eval_flag++;
621	break;
622	}
623	}
624	} while(0);
625
626	free(temp);
627
628	if(convert<2) {
629	free(rest);
630	return;
631	}
632
633	stack_read(env, rest);
634
635	free(rest);
636	}
637
638	/* Relocate elements of the list on the stack. */
639	extern void expand(environment *env)
640	{
641	stackitem temp, new_head;
642
643	/* Is top element a list? */
644	if(env->head==NULL) {
645	printerr("Too Few Arguments");
646	env->err=1;
647	return;
648	}
649	if(env->head->item->type!=list) {
650	printerr("Bad Argument Type");
651	env->err=2;
652	return;
653	}
654
655	rev(env);
656
657	if(env->err)
658	return;
659
660	/* The first list element is the new stack head */
661	new_head= temp= env->head->item->content.ptr;
662
663	env->head->item->refcount++;
664	toss(env);
665
666	/* Find the end of the list */
667	while(temp->next!=NULL)
668	temp= temp->next;
669
670	/* Connect the tail of the list with the old stack head */
671	temp->next= env->head;
672	env->head= new_head; /* ...and voila! */
673
674	}
675
676	/* Compares two elements by reference. */
677	extern void eq(environment *env)
678	{
679	void left, right;
680	int result;
681
682	if((env->head)==NULL \|\| env->head->next==NULL) {
683	printerr("Too Few Arguments");
684	env->err=1;
685	return;
686	}
687
688	left= env->head->item->content.ptr;
689	swap(env);
690	right= env->head->item->content.ptr;
691	result= (left==right);
692
693	toss(env); toss(env);
694	push_int(&(env->head), result);
695	}
696
697	/* Negates the top element on the stack. */
698	extern void not(environment *env)
699	{
700	int val;
701
702	if((env->head)==NULL) {
703	printerr("Too Few Arguments");
704	env->err=1;
705	return;
706	}
707
708	if(env->head->item->type!=integer) {
709	printerr("Bad Argument Type");
710	env->err=2;
711	return;
712	}
713
714	val= env->head->item->content.val;
715	toss(env);
716	push_int(&(env->head), !val);
717	}
718
719	/* Compares the two top elements on the stack and return 0 if they're the
720	same. */
721	extern void neq(environment *env)
722	{
723	eq(env);
724	not(env);
725	}
726
727	/* Give a symbol some content. */
728	extern void def(environment *env)
729	{
730	symbol *sym;
731
732	/* Needs two values on the stack, the top one must be a symbol */
733	if(env->head==NULL \|\| env->head->next==NULL) {
734	printerr("Too Few Arguments");
735	env->err=1;
736	return;
737	}
738
739	if(env->head->item->type!=symb) {
740	printerr("Bad Argument Type");
741	env->err=2;
742	return;
743	}
744
745	/* long names are a pain */
746	sym=env->head->item->content.ptr;
747
748	/* if the symbol was bound to something else, throw it away */
749	if(sym->val != NULL)
750	free_val(sym->val);
751
752	/* Bind the symbol to the value */
753	sym->val= env->head->next->item;
754	sym->val->refcount++; /* Increase the reference counter */
755
756	toss(env); toss(env);
757	}
758
759	/* Quit stack. */
760	extern void quit(environment *env)
761	{
762	exit(EXIT_SUCCESS);
763	}
764
765	/* Clear stack */
766	extern void clear(environment *env)
767	{
768	while(env->head!=NULL)
769	toss(env);
770	}
771
772	/* List all defined words */
773	extern void words(environment *env)
774	{
775	symbol *temp;
776	int i;
777
778	for(i= 0; i<HASHTBLSIZE; i++) {
779	temp= env->symbols[i];
780	while(temp!=NULL) {
781	printf("%s\n", temp->id);
782	temp= temp->next;
783	}
784	}
785	}
786
787	/* Forgets a symbol (remove it from the hash table) */
788	extern void forget(environment *env)
789	{
790	char* sym_id;
791	stackitem *stack_head= env->head;
792	symbol *hash_entry, temp;
793
794	if(stack_head==NULL) {
795	printerr("Too Few Arguments");
796	env->err=1;
797	return;
798	}
799
800	if(stack_head->item->type!=symb) {
801	printerr("Bad Argument Type");
802	env->err=2;
803	return;
804	}
805
806	sym_id= ((symbol*)(stack_head->item->content.ptr))->id;
807	toss(env);
808
809	hash_entry= hash(env->symbols, sym_id);
810	temp= *hash_entry;
811	hash_entry= (hash_entry)->next;
812
813	if(temp->val!=NULL) {
814	free_val(temp->val);
815	}
816	free(temp->id);
817	free(temp);
818	}
819
820	/* Returns the current error number to the stack */
821	extern void errn(environment *env){
822	push_int(&(env->head), env->err);
823	}
824
825	int main()
826	{
827	environment myenv;
828	char in_string[100];
829
830	init_env(&myenv);
831
832	printf("okidok\n ");
833
834	while(fgets(in_string, 100, stdin) != NULL) {
835	stack_read(&myenv, in_string);
836	if(myenv.err) {
837	printf("(error %d) ", myenv.err);
838	myenv.err=0;
839	}
840	printf("okidok\n ");
841	}
842	quit(&myenv);
843	return EXIT_FAILURE;
844	}