--- stack/stack.c	2002/01/08 18:06:19	1.11
+++ stack/stack.c	2002/02/13 00:47:36	1.76
@@ -1,46 +1,140 @@
-/* printf */
+/* printf, sscanf, fgets, fprintf */
 #include <stdio.h>
-/* EXIT_SUCCESS */
+/* exit, EXIT_SUCCESS, malloc, free */
 #include <stdlib.h>
 /* NULL */
 #include <stddef.h>
 /* dlopen, dlsym, dlerror */
 #include <dlfcn.h>
+/* strcmp, strcpy, strlen, strcat, strdup */
+#include <string.h>
 
-#define HASHTBLSIZE 65536
+#define HASHTBLSIZE 2048
 
-typedef struct stack_item
-{
-  enum {value, string, ref, func, symbol, list} type;
-  union {
-    void* ptr;
-    int val;
-  } content;
+/* First, define some types. */
+
+/* A value of some type */
+typedef struct {
+  enum {
+    integer,
+    string,
+    func,			/* Function pointer */
+    symb, 
+    list
+  } type;			/* Type of stack element */
 
-  char* id;
-  struct stack_item* next;
+  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 */
+				/* (This is never NULL) */
+  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;
+  char *in_string;		/* Input pending to be read */
+} 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->in_string= NULL;
+  env->err= 0;
+  env->non_eval_flag= 0;
+  for(i= 0; i<HASHTBLSIZE; i++)
+    env->symbols[i]= NULL;
+}
 
-typedef stackitem* hashtbl[HASHTBLSIZE];
-typedef void (*funcp)(stackitem**);
+void printerr(const char* in_string) {
+  fprintf(stderr, "Err: %s\n", in_string);
+}
 
-void init_hashtbl(hashtbl out_hash)
-{
-  long i;
+/* Throw away a value */
+void free_val(value *val){
+  stackitem *item, *temp;
 
-  for(i= 0; i<HASHTBLSIZE; i++)
-    out_hash[i]= NULL;
+  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;
+    case integer:
+    case func:
+    case symb:
+      break;
+    }
+  }
 }
 
-stackitem** hash(hashtbl in_hashtbl, const char* in_string)
+/* Discard the top element of the stack. */
+extern void toss(environment *env)
 {
-  long i= 0;
-  unsigned long out_hash= 0;
-  char key= 0;
-  stackitem** position;
+  stackitem *temp= env->head;
+
+  if((env->head)==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
   
-  while(1){
+  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 */
+}
+
+/* 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;
@@ -51,332 +145,1089 @@
   position= &(in_hashtbl[out_hash]);
 
   while(1){
-    if(*position==NULL)
+    if(*position==NULL)		/* If empty */
       return position;
     
-    if(strcmp(in_string, (*position)->id)==0)
+    if(strcmp(in_string, (*position)->id)==0) /* If match */
       return position;
 
-    position= &((*position)->next);
+    position= &((*position)->next); /* Try next */
   }
 }
 
-
-int push(stackitem** stack_head, stackitem* in_item)
+/* Push a value onto the stack */
+void push_val(environment *env, value *val)
 {
-  in_item->next= *stack_head;
-  *stack_head= in_item;
-  return 1;
+  stackitem *new_item= malloc(sizeof(stackitem));
+  new_item->item= val;
+  val->refcount++;
+  new_item->next= env->head;
+  env->head= new_item;
 }
 
-int push_val(stackitem** stack_head, int in_val) 
+/* Push an integer onto the stack. */
+void push_int(environment *env, int in_val) 
 {
-  stackitem* new_item= malloc(sizeof(stackitem));
-  new_item->content.val= in_val;
-  new_item->type= value;
-
-  push(stack_head, new_item);
-  return 1;
-}
-
-int push_cstring(stackitem** stack_head, const char* in_string)
-{
-  stackitem* new_item= malloc(sizeof(stackitem));
-  new_item->content.ptr= malloc(strlen(in_string)+1);
-  strcpy(new_item->content.ptr, in_string);
-  new_item->type= string;
+  value *new_value= malloc(sizeof(value));
+  
+  new_value->content.val= in_val;
+  new_value->type= integer;
+  new_value->refcount=1;
 
-  push(stack_head, new_item);
-  return 1;
+  push_val(env, new_value);
 }
 
-int mk_hashentry(hashtbl in_hashtbl, stackitem* in_item, const char* id)
+/* Copy a string onto the stack. */
+void push_cstring(environment *env, const char *in_string)
 {
-  in_item->id= malloc(strlen(id)+1);
+  value *new_value= malloc(sizeof(value));
 
-  strcpy(in_item->id, id);
-  push(hash(in_hashtbl, id), in_item);
+  new_value->content.ptr= malloc(strlen(in_string)+1);
+  strcpy(new_value->content.ptr, in_string);
+  new_value->type= string;
+  new_value->refcount=1;
 
-  return 1;
+  push_val(env, new_value);
 }
 
-void def_func(hashtbl in_hashtbl, funcp in_func, const char* id)
-{
-  stackitem* temp= malloc(sizeof(stackitem));
+/* Mangle a symbol name to a valid C identifier name */
+char *mangle_str(const char *old_string){
+  char validchars[]
+    ="0123456789abcdef";
+  char *new_string, *current;
 
-  temp->type= func;
-  temp->content.ptr= in_func;
-
-  mk_hashentry(in_hashtbl, temp, id);
-}
-
-void def_sym(hashtbl in_hashtbl, const char* id)
-{
-  stackitem* temp= malloc(sizeof(stackitem));
-  
-  temp->type= symbol;
+  new_string=malloc((strlen(old_string)*2)+4);
+  strcpy(new_string, "sx_");	/* Stack eXternal */
+  current=new_string+3;
+  while(old_string[0] != '\0'){
+    current[0]=validchars[(unsigned char)(old_string[0])/16];
+    current[1]=validchars[(unsigned char)(old_string[0])%16];
+    current+=2;
+    old_string++;
+  }
+  current[0]='\0';
 
-  mk_hashentry(in_hashtbl, temp, id);
+  return new_string;		/* The caller must free() it */
 }
 
-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;
+extern void mangle(environment *env){
+  value *new_value;
+  char *new_string;
 
-  if(new_item->content.ptr==NULL) {
-    if(handle==NULL)
-      handle= dlopen(NULL, RTLD_LAZY);    
-
-    symbol= dlsym(handle, in_string);
-    if(dlerror()==NULL) 
-      def_func(in_hash, symbol, in_string);
-    else
-      def_sym(in_hash, in_string);
-      
-    new_item->content.ptr= *hash(in_hash, in_string);
-    new_item->type= ref;
+  if((env->head)==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
   }
 
-  push(stack_head, new_item);
-  return 1;
-}
+  if(env->head->item->type!=string) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
 
-extern void toss(stackitem** stack_head)
-{
-  stackitem* temp= *stack_head;
+  new_string= mangle_str((const char *)(env->head->item->content.ptr));
 
-  if((*stack_head)==NULL)
-    return;
-  
-  if((*stack_head)->type==string)
-    free((*stack_head)->content.ptr);
+  toss(env);
+  if(env->err) return;
 
-  *stack_head= (*stack_head)->next;
-  free(temp);
+  new_value= malloc(sizeof(value));
+  new_value->content.ptr= new_string;
+  new_value->type= string;
+  new_value->refcount=1;
+
+  push_val(env, new_value);
+}
+
+/* Push a symbol onto the stack. */
+void push_sym(environment *env, const char *in_string)
+{
+  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 */
+  const char *dlerr;		/* Dynamic linker error */
+  char *mangled;		/* Mangled function name */
+
+  new_value= malloc(sizeof(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 */
+    dlerr=dlerror();
+    if(dlerr != NULL) {		/* If no function was found */
+      mangled=mangle_str(in_string);
+      funcptr= dlsym(handle, mangled); /* try mangling it */
+      free(mangled);
+      dlerr=dlerror();
+    }
+    if(dlerr==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_val(env, new_value);
 }
 
+/* Print newline. */
 extern void nl()
 {
   printf("\n");
 }
 
-void print_(stackitem** stack_head)
-{
-  if((*stack_head)==NULL)
+/* 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;
+  }
+}    
 
-  switch((*stack_head)->type) {
-  case value:
-    printf("%d", (*stack_head)->content.val);
+/* 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)->content.ptr);
+    printf("%s", (char*)stack_head->item->content.ptr);
     break;
-  case ref:
-    printf("%s", ((stackitem*)(*stack_head)->content.ptr)->id);
+  case symb:
+    printf("%s", ((symbol *)(stack_head->item->content.ptr))->id);
     break;
-  case symbol:
-  default:
-    printf("%p", (*stack_head)->content.ptr);
+  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;
   }
 }
 
-extern void print(stackitem** stack_head)
+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_(stack_head);
-  toss(stack_head);
+  print_(env);
+  if(env->err) return;
+  toss(env);
 }
 
-/* print_stack(stack); */
-void print_st(stackitem* stack_head, long counter)
+/* Only to be called by function printstack. */
+void print_st(stackitem *stack_head, long counter)
 { 
   if(stack_head->next != NULL)
     print_st(stack_head->next, counter+1);
-
   printf("%ld: ", counter);
-  print_(&stack_head);
+  print_h(stack_head);
   nl();
 }
 
-extern void printstack(stackitem** stack_head)
+/* Prints the stack. */
+extern void printstack(environment *env)
 {
-  if(*stack_head != NULL) {
-    print_st(*stack_head, 1);
-    printf("\n");
+  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;
+} 
 
-extern void eval(stackitem** stack_head)
+/* Rotate the first three elements on the stack. */
+extern void rot(environment *env)
 {
-  funcp in_func;
+  stackitem *temp= env->head;
+  
+  if(env->head==NULL || env->head->next==NULL
+      || env->head->next->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+
+  env->head= env->head->next->next;
+  temp->next->next= env->head->next;
+  env->head->next= temp;
+}
+
+/* Recall a value from a symbol, if bound */
+extern void rcl(environment *env)
+{
+  value *val;
 
-  if((*stack_head)==NULL || (*stack_head)->type!=ref)
+  if(env->head == NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
+  }
 
-  if(((stackitem*)(*stack_head)->content.ptr)->type==func) {
-    in_func= (funcp)((stackitem*)(*stack_head)->content.ptr)->content.ptr;
-    toss(stack_head); 
-    (*in_func)(stack_head);
+  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, val); /* Return its bound value */
 }
 
-int stack_read(stackitem** stack_head, hashtbl in_hash, char* in_line) 
+/* 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)
 {
-  char *temp, *rest;
-  int itemp;
-  size_t inlength= strlen(in_line)+1;
-  int convert= 0;
+  funcp in_func;
+  value* temp_val;
+  stackitem* iterator;
 
-  temp= malloc(inlength);
-  rest= malloc(inlength);
+  if(env->head==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
 
-  if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest)) >= 1)
-    push_cstring(stack_head, temp);
-  else if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest)) >= 1)
-    push_val(stack_head, itemp);
-  else if((convert= sscanf(in_line, "%[^ ;\n\r]%[^\n\r]", temp, rest)) >= 1) 
-    push_ref(stack_head, in_hash, temp);
-  else if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest)) >= 1)
-    if(*temp==';')
-      eval(stack_head);
+ eval_start:
 
-  free(temp);
+  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 */
+      goto eval_start;
+    }
+    return;
 
-  if(convert<2) {
-    free(rest);
-    return 0;
+    /* 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;
+    return (*in_func)(env);
+
+    /* 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) {
+      push_val(env, iterator->item);
+      if(env->head->item->type==symb
+	&& strcmp(";", ((symbol*)(env->head->item->content.ptr))->id)==0) {
+	toss(env);
+	if(env->err) return;
+	if(iterator->next == NULL){
+	  free_val(temp_val);
+	  goto eval_start;
+	}
+	eval(env);
+	if(env->err) return;
+      }
+      iterator= iterator->next;
+    }
+    free_val(temp_val);
+    return;
+
+  default:
+    return;
   }
-   
-  stack_read(stack_head, in_hash, rest);
-  
-  free(rest);
-  return 1;
 }
 
-extern void pack(stackitem** stack_head)
-{
-  void* delimiter;
-  stackitem *iterator, *temp, *pack;
-
-  if((*stack_head)==NULL)
+/* Reverse (flip) a list */
+extern void rev(environment *env){
+  stackitem *item, *temp, *prev= NULL;
+
+  if((env->head)==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
+  }
 
-  delimiter= (*stack_head)->content.ptr;
-  toss(stack_head);
+  if(env->head->item->type!=list) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
 
-  iterator= *stack_head;
+  item= (stackitem *)(env->head->item->content.ptr);
+  while(item->next!=NULL){
+    temp= item->next;
+    item->next= prev;
+    prev= item;
+    item= temp;
+  }
+  item->next= prev;
 
-  while(iterator->next!=NULL && iterator->next->content.ptr!=delimiter)
-    iterator= iterator->next;
+  env->head->item->content.ptr=item;
+}
 
-  temp= *stack_head;
-  *stack_head= iterator->next;
-  iterator->next= NULL;
-  
-  if(*stack_head!=NULL && (*stack_head)->content.ptr==delimiter)
-    toss(stack_head);
+/* Make a list. */
+extern void pack(environment *env)
+{
+  stackitem *iterator, *temp;
+  value *pack;
+
+  iterator= env->head;
+
+  if(iterator==NULL
+     || (iterator->item->type==symb
+     && ((symbol*)(iterator->item->content.ptr))->id[0]=='[')) {
+    temp= NULL;
+    toss(env);
+  } else {
+    /* Search for first delimiter */
+    while(iterator->next!=NULL
+	  && (iterator->next->item->type!=symb
+	  || ((symbol*)(iterator->next->item->content.ptr))->id[0]!='['))
+      iterator= iterator->next;
+    
+    /* Extract list */
+    temp= env->head;
+    env->head= iterator->next;
+    iterator->next= NULL;
+    
+    if(env->head!=NULL)
+      toss(env);
+  }
 
-  pack= malloc(sizeof(stackitem));
+  /* Push list */
+  pack= malloc(sizeof(value));
   pack->type= list;
   pack->content.ptr= temp;
+  pack->refcount= 1;
 
-  push(stack_head, pack);
+  push_val(env, pack);
+  rev(env);
 }
 
-extern void expand(stackitem** stack_head)
+/* Relocate elements of the list on the stack. */
+extern void expand(environment *env)
 {
   stackitem *temp, *new_head;
 
-  if((*stack_head)==NULL || (*stack_head)->type!=list)
+  /* 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;
 
-  new_head= temp= (*stack_head)->content.ptr;
-  toss(stack_head);
+  /* 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;
 
-  temp->next= *stack_head;
-  *stack_head= new_head;
-}
+  /* Connect the tail of the list with the old stack head */
+  temp->next= env->head;
+  env->head= new_head;		/* ...and voila! */
 
-extern void swap(stackitem** stack_head)
-{
-  stackitem* temp= (*stack_head);
-  
-  if((*stack_head)==NULL || (*stack_head)->next==NULL)
-    return;
-
-  *stack_head= (*stack_head)->next;
-  temp->next= (*stack_head)->next;
-  (*stack_head)->next= temp;
-} 
+}
 
-extern void eq(stackitem** stack_head)
+/* Compares two elements by reference. */
+extern void eq(environment *env)
 {
   void *left, *right;
   int result;
 
-  if((*stack_head)==NULL || (*stack_head)->next==NULL)
+  if((env->head)==NULL || env->head->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
+  }
 
-  left= (*stack_head)->content.ptr;
-  right= (*stack_head)->next->content.ptr;
+  left= env->head->item->content.ptr;
+  swap(env);
+  right= env->head->item->content.ptr;
   result= (left==right);
   
-  toss(stack_head); toss(stack_head);
-  push_val(stack_head, (left==right));
+  toss(env); toss(env);
+  push_int(env, result);
 }
 
-extern void not(stackitem** stack_head)
+/* Negates the top element on the stack. */
+extern void not(environment *env)
 {
-  int value;
+  int val;
 
-  if((*stack_head)==NULL)
+  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;
+  }
 
-  value= (*stack_head)->content.val;
-  toss(stack_head);
-  push_val(stack_head, !value);
+  val= env->head->item->content.val;
+  toss(env);
+  push_int(env, !val);
 }
 
-extern void neq(stackitem** stack_head)
+/* Compares the two top elements on the stack and return 0 if they're the
+   same. */
+extern void neq(environment *env)
 {
-  eq(stack_head);
-  not(stack_head);
+  eq(env);
+  not(env);
 }
 
-extern void quit()
+/* 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, env->err);
+}
+
+extern void read(environment*);
+
 int main()
 {
-  stackitem* s= NULL;
-  hashtbl myhash;
-  char in_string[100];
+  environment myenv;
 
-  init_hashtbl(myhash);
+  init_env(&myenv);
 
-  printf("okidok\n ");
+  while(1) {
+    if(myenv.in_string==NULL)
+      printstack(&myenv);
+    read(&myenv);
+    if(myenv.err) {
+      printf("(error %d) ", myenv.err);
+      myenv.err=0;
+    } else if(myenv.head!=NULL
+	      && myenv.head->item->type==symb
+	      && ((symbol*)(myenv.head->item->content.ptr))->id[0]==';') {
+      toss(&myenv); 		/* No error check in main */
+      eval(&myenv);
+    }
+  }
+  quit(&myenv);
+  return EXIT_FAILURE;
+}
 
-  while(fgets(in_string, 100, stdin) != NULL) {
-    stack_read(&s, myhash, in_string);
-    printf("okidok\n ");
+/* + */
+extern void sx_2b(environment *env) {
+  int a, b;
+  size_t len;
+  char* new_string;
+  value *a_val, *b_val;
+
+  if((env->head)==NULL || env->head->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
   }
 
-  exit(EXIT_SUCCESS);
+  if(env->head->item->type==string
+     && env->head->next->item->type==string) {
+    a_val= env->head->item;
+    b_val= env->head->next->item;
+    a_val->refcount++;
+    b_val->refcount++;
+    toss(env); if(env->err) return;
+    toss(env); if(env->err) return;
+    len= strlen(a_val->content.ptr)+strlen(b_val->content.ptr)+1;
+    new_string= malloc(len);
+    strcpy(new_string, b_val->content.ptr);
+    strcat(new_string, a_val->content.ptr);
+    free_val(a_val); free_val(b_val);
+    push_cstring(env, new_string);
+    free(new_string);
+    return;
+  }
+  
+  if(env->head->item->type!=integer
+     || env->head->next->item->type!=integer) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
+  a=env->head->item->content.val;
+  toss(env);
+  if(env->err) return;
+  if(env->head->item->refcount == 1)
+    env->head->item->content.val += a;
+  else {
+    b=env->head->item->content.val;
+    toss(env);
+    if(env->err) return;
+    push_int(env, a+b);
+  }
+}
+
+/* - */
+extern void sx_2d(environment *env) {
+  int a, b;
+
+  if((env->head)==NULL || env->head->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+  
+  if(env->head->item->type!=integer
+     || env->head->next->item->type!=integer) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
+  a=env->head->item->content.val;
+  toss(env);
+  if(env->err) return;
+  if(env->head->item->refcount == 1)
+    env->head->item->content.val -= a;
+  else {
+    b=env->head->item->content.val;
+    toss(env);
+    if(env->err) return;
+    push_int(env, b-a);
+  }
+}
+
+/* > */
+extern void sx_3e(environment *env) {
+  int a, b;
+
+  if((env->head)==NULL || env->head->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+  
+  if(env->head->item->type!=integer
+     || env->head->next->item->type!=integer) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
+  a=env->head->item->content.val;
+  toss(env);
+  if(env->err) return;
+  if(env->head->item->refcount == 1)
+    env->head->item->content.val = (env->head->item->content.val > a);
+  else {
+    b=env->head->item->content.val;
+    toss(env);
+    if(env->err) return;
+    push_int(env, b>a);
+  }
+}
+
+/* Return copy of a value */
+value *copy_val(value *old_value){
+  stackitem *old_item, *new_item, *prev_item;
+
+  value *new_value=malloc(sizeof(value));
+
+  new_value->type=old_value->type;
+  new_value->refcount=0;	/* This is increased if/when this
+				   value is referenced somewhere, like
+				   in a stack item or a variable */
+  switch(old_value->type){
+  case integer:
+    new_value->content.val=old_value->content.val;
+    break;
+  case string:
+    (char *)(new_value->content.ptr)
+      = strdup((char *)(old_value->content.ptr));
+    break;
+  case func:
+  case symb:
+    new_value->content.ptr=old_value->content.ptr;
+    break;
+  case list:
+    new_value->content.ptr=NULL;
+
+    prev_item=NULL;
+    old_item=(stackitem *)(old_value->content.ptr);
+
+    while(old_item != NULL) {	/* While list is not empty */
+      new_item= malloc(sizeof(stackitem));
+      new_item->item=copy_val(old_item->item); /* recurse */
+      new_item->next=NULL;
+      if(prev_item != NULL)	/* If this wasn't the first item */
+	prev_item->next=new_item; /* point the previous item to the
+                                     new item */
+      else
+	new_value->content.ptr=new_item;
+      old_item=old_item->next;
+      prev_item=new_item;
+    }	  
+    break;
+  }
+  return new_value;
+}
+
+/* duplicates an item on the stack */
+extern void dup(environment *env) {
+  if((env->head)==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+  push_val(env, copy_val(env->head->item));
+}
+
+/* "if", If-Then */
+extern void sx_6966(environment *env) {
+
+  int truth;
+
+  if((env->head)==NULL || env->head->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+
+  if(env->head->next->item->type != integer) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
+  
+  swap(env);
+  if(env->err) return;
+  
+  truth=env->head->item->content.val;
+
+  toss(env);
+  if(env->err) return;
+
+  if(truth)
+    eval(env);
+  else
+    toss(env);
+}
+
+/* If-Then-Else */
+extern void ifelse(environment *env) {
+
+  int truth;
+
+  if((env->head)==NULL || env->head->next==NULL
+     || env->head->next->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+
+  if(env->head->next->next->item->type != integer) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
+  
+  rot(env);
+  if(env->err) return;
+  
+  truth=env->head->item->content.val;
+
+  toss(env);
+  if(env->err) return;
+
+  if(!truth)
+    swap(env);
+  if(env->err) return;
+
+  toss(env);
+  if(env->err) return;
+
+  eval(env);
+}
+
+/* while */
+extern void sx_7768696c65(environment *env) {
+
+  int truth;
+  value *loop, *test;
+
+  if((env->head)==NULL || env->head->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+
+  loop= env->head->item;
+  loop->refcount++;
+  toss(env); if(env->err) return;
+
+  test= env->head->item;
+  test->refcount++;
+  toss(env); if(env->err) return;
+
+  do {
+    push_val(env, test);
+    eval(env);
+    
+    if(env->head->item->type != integer) {
+      printerr("Bad Argument Type");
+      env->err=2;
+      return;
+    }
+    
+    truth= env->head->item->content.val;
+    toss(env); if(env->err) return;
+    
+    if(truth) {
+      push_val(env, loop);
+      eval(env);
+    } else {
+      toss(env);
+    }
+  
+  } while(truth);
+
+  free_val(test);
+  free_val(loop);
+}
+
+/* For-loop */
+extern void sx_666f72(environment *env) {
+  
+  value *loop, *foo;
+  stackitem *iterator;
+  
+  if((env->head)==NULL || env->head->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+
+  if(env->head->next->item->type != list) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
+
+  loop= env->head->item;
+  loop->refcount++;
+  toss(env); if(env->err) return;
+
+  foo= env->head->item;
+  foo->refcount++;
+  toss(env); if(env->err) return;
+
+  iterator= foo->content.ptr;
+
+  while(iterator!=NULL) {
+    push_val(env, iterator->item);
+    push_val(env, loop);
+    eval(env); if(env->err) return;
+    iterator= iterator->next;
+  }
+
+  free_val(loop);
+  free_val(foo);
 }
 
-/* Local Variables: */
-/* compile-command:"make CFLAGS=\"-Wall -g -rdynamic -ldl\" stack" */
-/* End: */
+/* 'to' */
+extern void to(environment *env) {
+  int i, start, ending;
+  stackitem *temp_head;
+  value *temp_val;
+  
+  if((env->head)==NULL || env->head->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+
+  if(env->head->item->type!=integer 
+     || env->head->next->item->type!=integer) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
+
+  ending= env->head->item->content.val;
+  toss(env); if(env->err) return;
+  start= env->head->item->content.val;
+  toss(env); if(env->err) return;
+
+  temp_head= env->head;
+  env->head= NULL;
+
+  if(ending>=start) {
+    for(i= ending; i>=start; i--)
+      push_int(env, i);
+  } else {
+    for(i= ending; i<=start; i++)
+      push_int(env, i);
+  }
+
+  temp_val= malloc(sizeof(value));
+  temp_val->content.ptr= env->head;
+  temp_val->refcount= 1;
+  temp_val->type= list;
+  env->head= temp_head;
+  push_val(env, temp_val);
+}
+
+/* Read a string */
+extern void readline(environment *env) {
+  char in_string[101];
+
+  fgets(in_string, 100, stdin);
+  push_cstring(env, in_string);
+}
+
+/* Read a value and place on stack */
+extern void read(environment *env) {
+  const char symbform[]= "%[a-zA-Z0-9!$%*+./:<=>?@^_~-]%[\001-\377]";
+  const char strform[]= "\"%[^\"]\"%[\001-\377]";
+  const char intform[]= "%i%[\001-\377]";
+  const char blankform[]= "%*[ \t]%[\001-\377]";
+  const char ebrackform[]= "%*1[]]%[\001-\377]";
+  const char semicform[]= "%*1[;]%[\001-\377]";
+  const char bbrackform[]= "%*1[[]%[\001-\377]";
+
+  int itemp;
+  static int depth= 0;
+  char *rest, *match;
+  size_t inlength;
+
+  if(env->in_string==NULL) {
+    readline(env); if(env->err) return;
+    
+    env->in_string= malloc(strlen(env->head->item->content.ptr)+1);
+    strcpy(env->in_string, env->head->item->content.ptr);
+    toss(env); if(env->err) return;
+  }
+  
+  inlength= strlen(env->in_string)+1;
+  match= malloc(inlength);
+  rest= malloc(inlength);
+
+  if(sscanf(env->in_string, blankform, rest)) {
+    ; 
+  } else if(sscanf(env->in_string, intform, &itemp, rest) > 0) {
+    push_int(env, itemp);
+  } else if(sscanf(env->in_string, strform, match, rest) > 0) {
+    push_cstring(env, match);
+  } else if(sscanf(env->in_string, symbform, match, rest) > 0) {
+    push_sym(env, match);
+  } else if(sscanf(env->in_string, ebrackform, rest) > 0) {
+    pack(env); if(env->err) return;
+    if(depth!=0) depth--;
+  } else if(sscanf(env->in_string, semicform, rest) > 0) {
+    push_sym(env, ";");
+  } else if(sscanf(env->in_string, bbrackform, rest) > 0) {
+    push_sym(env, "[");
+    depth++;
+  } else {
+    free(rest);
+    rest= NULL;
+  }
+      
+  free(env->in_string);
+  free(match);
+
+  env->in_string= rest;
+
+  if(depth)
+    return read(env);
+}