--- stack/stack.c	2002/02/07 05:24:19	1.49
+++ stack/stack.c	2002/02/16 00:51:32	1.88
@@ -1,112 +1,44 @@
-/* printf */
+/* printf, sscanf, fgets, fprintf, fopen, perror */
 #include <stdio.h>
-/* EXIT_SUCCESS */
+/* exit, EXIT_SUCCESS, malloc, free */
 #include <stdlib.h>
 /* NULL */
 #include <stddef.h>
 /* dlopen, dlsym, dlerror */
 #include <dlfcn.h>
-/* assert */
-#include <assert.h>
-/* strcat */
+/* strcmp, strcpy, strlen, strcat, strdup */
 #include <string.h>
+/* getopt, STDIN_FILENO, STDOUT_FILENO */
+#include <unistd.h>
+/* EX_NOINPUT, EX_USAGE */
+#include <sysexits.h>
+/* mtrace, muntrace */
+#include <mcheck.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 *) */
+#include "stack.h"
 
 /* Initialize a newly created environment */
 void init_env(environment *env)
 {
   int i;
 
-  env->err= 0;
-  env->non_eval_flag= 0;
+  env->gc_limit= 20;
+  env->gc_count= 0;
+
+  env->head= NULL;
   for(i= 0; i<HASHTBLSIZE; i++)
     env->symbols[i]= NULL;
+  env->err= 0;
+  env->in_string= NULL;
+  env->free_string= NULL;
+  env->inputstream= stdin;
+  env->interactive= 1;
 }
 
 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)
 {
@@ -118,7 +50,6 @@
     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 */
 }
@@ -152,63 +83,149 @@
   }
 }
 
-/* Generic push function. */
-void push(stackitem** stack_head, stackitem* in_item)
-{
-  in_item->next= *stack_head;
-  *stack_head= in_item;
+value* new_val(environment *env) {
+  value *nval= malloc(sizeof(value));
+  stackitem *nitem= malloc(sizeof(stackitem));
+
+  if(env->gc_count >= env->gc_limit)
+    gc_init(env);
+
+  nval->content.ptr= NULL;
+
+  nitem->item= nval;
+  nitem->next= env->gc_ref;
+  env->gc_ref= nitem;
+
+  env->gc_count++;
+
+  return nval;
+}
+
+void gc_mark(value *val) {
+  stackitem *iterator;
+
+  if(val==NULL || val->gc_garb==0)
+    return;
+
+  val->gc_garb= 0;
+
+  if(val->type==list) {
+    iterator= val->content.ptr;
+
+    while(iterator!=NULL) {
+      gc_mark(iterator->item);
+      iterator= iterator->next;
+    }
+  }
+}
+
+extern void gc_init(environment *env) {
+  stackitem *new_head= NULL, *titem, *iterator= env->gc_ref;
+  symbol *tsymb;
+  int i;
+
+  while(iterator!=NULL) {
+    iterator->item->gc_garb= 1;
+    iterator= iterator->next;
+  }
+
+  /* Mark */
+  iterator= env->head;
+  while(iterator!=NULL) {
+    gc_mark(iterator->item);
+    iterator= iterator->next;
+  }
+
+  for(i= 0; i<HASHTBLSIZE; i++) {
+    tsymb= env->symbols[i];
+    while(tsymb!=NULL) {
+      gc_mark(tsymb->val);
+      tsymb= tsymb->next;
+    }
+  }
+
+  env->gc_count= 0;
+
+  /* Sweep */
+  while(env->gc_ref!=NULL) {
+    if(env->gc_ref->item->gc_garb) {
+      switch(env->gc_ref->item->type) {
+      case string:
+	free(env->gc_ref->item->content.ptr);
+	break;
+      case integer:
+	break;
+      case list:
+	while(env->gc_ref->item->content.ptr!=NULL) {
+	  titem= env->gc_ref->item->content.ptr;
+	  env->gc_ref->item->content.ptr= titem->next;
+	  free(titem);
+	}
+	break;
+      default:
+	break;
+      }
+      free(env->gc_ref->item);
+      titem= env->gc_ref->next;
+      free(env->gc_ref);
+      env->gc_ref= titem;
+    } else {
+      titem= env->gc_ref->next;
+      env->gc_ref->next= new_head;
+      new_head= env->gc_ref;
+      env->gc_ref= titem;
+      env->gc_count++;
+    }
+  }
+
+  env->gc_limit= env->gc_count+20;
+  env->gc_ref= new_head;
 }
 
 /* Push a value onto the stack */
-void push_val(stackitem **stack_head, value *val)
+void push_val(environment *env, value *val)
 {
   stackitem *new_item= malloc(sizeof(stackitem));
   new_item->item= val;
-  val->refcount++;
-  push(stack_head, new_item);
+  new_item->next= env->head;
+  env->head= new_item;
 }
 
 /* Push an integer onto the stack. */
-void push_int(stackitem **stack_head, int in_val) 
+void push_int(environment *env, int in_val) 
 {
-  value *new_value= malloc(sizeof(value));
-  stackitem *new_item= malloc(sizeof(stackitem));
-  new_item->item= new_value;
+  value *new_value= new_val(env);
   
   new_value->content.val= in_val;
   new_value->type= integer;
-  new_value->refcount=1;
 
-  push(stack_head, new_item);
+  push_val(env, new_value);
 }
 
 /* Copy a string onto the stack. */
-void push_cstring(stackitem **stack_head, const char *in_string)
+void push_cstring(environment *env, const char *in_string)
 {
-  value *new_value= malloc(sizeof(value));
-  stackitem *new_item= malloc(sizeof(stackitem));
-  new_item->item=new_value;
+  value *new_value= new_val(env);
 
   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_val(env, new_value);
 }
 
 /* Mangle a symbol name to a valid C identifier name */
-char *mangle_(const char *old_string){
+char *mangle_str(const char *old_string){
   char validchars[]
     ="0123456789abcdef";
   char *new_string, *current;
 
-  new_string=malloc(strlen(old_string)+4);
+  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[old_string[0]/16];
-    current[1]=validchars[old_string[0]%16];
+    current[0]=validchars[(unsigned char)(old_string[0])/16];
+    current[1]=validchars[(unsigned char)(old_string[0])%16];
     current+=2;
     old_string++;
   }
@@ -218,7 +235,6 @@
 }
 
 extern void mangle(environment *env){
-  value *new_value;
   char *new_string;
 
   if((env->head)==NULL) {
@@ -233,24 +249,17 @@
     return;
   }
 
-  new_string= mangle_((const char *)(env->head->item->content.ptr));
+  new_string= mangle_str((const char *)(env->head->item->content.ptr));
 
   toss(env);
   if(env->err) return;
 
-  new_value= malloc(sizeof(value));
-  new_value->content.ptr= new_string;
-  new_value->type= string;
-  new_value->refcount=1;
-
-  push_val(&(env->head), new_value);
+  push_cstring(env, new_string);
 }
 
 /* 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 */
@@ -263,14 +272,10 @@
   const char *dlerr;		/* Dynamic linker error */
   char *mangled;		/* Mangled function name */
 
-  /* Create a new stack item containing a new value */
-  new_item= malloc(sizeof(stackitem));
-  new_value= malloc(sizeof(value));
-  new_item->item=new_value;
+  new_value= new_val(env);
 
   /* 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);
@@ -293,24 +298,23 @@
     if(handle==NULL)		/* If no handle */
       handle= dlopen(NULL, RTLD_LAZY);
 
-    funcptr= dlsym(handle, in_string); /* Get function pointer */
+    mangled=mangle_str(in_string); /* mangle the name */
+    funcptr= dlsym(handle, mangled); /* and try to find it */
+    free(mangled);
     dlerr=dlerror();
     if(dlerr != NULL) {		/* If no function was found */
-      mangled=mangle_(in_string);
-      funcptr= dlsym(handle, mangled); /* try mangling it */
-      free(mangled);
+      funcptr= dlsym(handle, in_string); /* Get function pointer */
       dlerr=dlerror();
     }
     if(dlerr==NULL) {		/* If a function was found */
-      new_fvalue= malloc(sizeof(value)); /* Create a new value */
+      new_fvalue= new_val(env); /* 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);
+  push_val(env, new_value);
 }
 
 /* Print newline. */
@@ -346,21 +350,21 @@
   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)
+void print_h(stackitem *stack_head, int noquote)
 {
   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);
+    if(noquote)
+      printf("%s", (char*)stack_head->item->content.ptr);
+    else
+      printf("\"%s\"", (char*)stack_head->item->content.ptr);
     break;
   case symb:
     printf("%s", ((symbol *)(stack_head->item->content.ptr))->id);
@@ -373,15 +377,12 @@
     stack_head=(stackitem *)(stack_head->item->content.ptr);
     printf("[ ");
     while(stack_head != NULL) {
-      print_h(stack_head);
+      print_h(stack_head, noquote);
       printf(" ");
       stack_head=stack_head->next;
     }
     printf("]");
     break;
-  default:
-    printf("#<unknown %p>", (stack_head->item->content.ptr));
-    break;
   }
 }
 
@@ -391,7 +392,8 @@
     env->err=1;
     return;
   }
-  print_h(env->head);
+  print_h(env->head, 0);
+  nl();
 }
 
 /* Prints the top element of the stack and then discards it. */
@@ -402,13 +404,30 @@
   toss(env);
 }
 
+extern void princ_(environment *env) {
+  if(env->head==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+  print_h(env->head, 1);
+}
+
+/* Prints the top element of the stack and then discards it. */
+extern void princ(environment *env)
+{
+  princ_(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);
+  print_h(stack_head, 0);
   nl();
 }
 
@@ -416,10 +435,10 @@
 extern void printstack(environment *env)
 {
   if(env->head == NULL) {
+    printf("Stack Empty\n");
     return;
   }
   print_st(env->head, 1);
-  nl();
 }
 
 /* Swap the two top elements on the stack. */
@@ -438,6 +457,23 @@
   env->head->next= temp;
 } 
 
+/* Rotate the first three elements on the stack. */
+extern void rot(environment *env)
+{
+  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)
 {
@@ -463,11 +499,9 @@
   }
   toss(env);		/* toss the symbol */
   if(env->err) return;
-  push_val(&(env->head), val); /* Return its bound value */
+  push_val(env, val); /* Return its bound value */
 }
 
-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. */
@@ -476,7 +510,8 @@
   funcp in_func;
   value* temp_val;
   stackitem* iterator;
-  char* temp_string;
+
+ eval_start:
 
   if(env->head==NULL) {
     printerr("Too Few Arguments");
@@ -490,58 +525,41 @@
     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;
+      goto eval_start;
     }
-    break;
+    return;
 
     /* 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;
+    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 && iterator->item!=NULL) {
-      push_val(&(env->head), iterator->item);
+    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){
+	  goto eval_start;
+	}
 	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;
-    temp_string= malloc(strlen((char*)temp_val->content.ptr)+5);
-    strcpy(temp_string, "[ ");
-    strcat(temp_string, (char*)temp_val->content.ptr);
-    strcat(temp_string, " ]");
-    stack_read(env, temp_string);
-    eval(env);
-    if(env->err) return;
-    free_val(temp_val);
-    free(temp_string);
-    break;
+    return;
 
   default:
+    return;
   }
 }
 
@@ -575,22 +593,21 @@
 /* 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) {
+  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->content.ptr!=delimiter)
+	  && (iterator->next->item->type!=symb
+	  || ((symbol*)(iterator->next->item->content.ptr))->id[0]!='['))
       iterator= iterator->next;
     
     /* Extract list */
@@ -603,97 +620,14 @@
   }
 
   /* Push list */
-  pack= malloc(sizeof(value));
+  pack= new_val(env);
   pack->type= list;
   pack->content.ptr= temp;
-  pack->refcount= 1;
-
-  temp= malloc(sizeof(stackitem));
-  temp->item= pack;
 
-  push(&(env->head), temp);
+  push_val(env, pack);
   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)
 {
@@ -719,7 +653,6 @@
   /* 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 */
@@ -750,7 +683,7 @@
   result= (left==right);
   
   toss(env); toss(env);
-  push_int(&(env->head), result);
+  push_int(env, result);
 }
 
 /* Negates the top element on the stack. */
@@ -772,7 +705,7 @@
 
   val= env->head->item->content.val;
   toss(env);
-  push_int(&(env->head), !val);
+  push_int(env, !val);
 }
 
 /* Compares the two top elements on the stack and return 0 if they're the
@@ -805,12 +738,9 @@
   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);
 } 
@@ -818,6 +748,25 @@
 /* Quit stack. */
 extern void quit(environment *env)
 {
+  long i;
+
+  clear(env);
+
+  if (env->err) return;
+  for(i= 0; i<HASHTBLSIZE; i++) {
+    while(env->symbols[i]!= NULL) {
+      forget_sym(&(env->symbols[i]));
+    }
+    env->symbols[i]= NULL;
+  }
+
+  gc_init(env);
+
+  if(env->free_string!=NULL)
+    free(env->free_string);
+  
+  muntrace();
+
   exit(EXIT_SUCCESS);
 }
 
@@ -843,12 +792,22 @@
   }
 }
 
+/* Internal forget function */
+void forget_sym(symbol **hash_entry) {
+  symbol *temp;
+
+  temp= *hash_entry;
+  *hash_entry= (*hash_entry)->next;
+  
+  free(temp->id);
+  free(temp);
+}
+
 /* 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");
@@ -865,44 +824,77 @@
   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);
+  return forget_sym(hash(env->symbols, sym_id));
 }
 
 /* Returns the current error number to the stack */
 extern void errn(environment *env){
-  push_int(&(env->head), env->err);
+  push_int(env, env->err);
 }
 
-int main()
+int main(int argc, char **argv)
 {
   environment myenv;
-  char in_string[100];
+
+  int c;			/* getopt option character */
+
+  mtrace();
 
   init_env(&myenv);
 
-  printf("okidok\n ");
+  myenv.interactive = isatty(STDIN_FILENO) && isatty(STDOUT_FILENO);
+
+  while ((c = getopt (argc, argv, "i")) != -1)
+    switch (c)
+      {
+      case 'i':
+	myenv.interactive = 1;
+	break;
+      case '?':
+	fprintf (stderr,
+		 "Unknown option character `\\x%x'.\n",
+		 optopt);
+	return EX_USAGE;
+      default:
+	abort ();
+      }
+  
+  if (optind < argc) {
+    myenv.interactive = 0;
+    myenv.inputstream= fopen(argv[optind], "r");
+    if(myenv.inputstream== NULL) {
+      perror(argv[0]);
+      exit (EX_NOINPUT);
+    }
+  }
 
-  while(fgets(in_string, 100, stdin) != NULL) {
-    stack_read(&myenv, in_string);
-    if(myenv.err) {
-      printf("(error %d) ", myenv.err);
+  while(1) {
+    if(myenv.in_string==NULL) {
+      if (myenv.interactive) {
+	if(myenv.err) {
+	  printf("(error %d)\n", myenv.err);
+	}
+	nl();
+	printstack(&myenv);
+	printf("> ");
+      }
       myenv.err=0;
     }
-    printf("okidok\n ");
+    sx_72656164(&myenv);
+    if (myenv.err==4) {
+      return EX_NOINPUT;
+    } 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;
 }
 
-/* + */
+/* "+" */
 extern void sx_2b(environment *env) {
   int a, b;
   size_t len;
@@ -919,16 +911,13 @@
      && 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->head), new_string);
+    push_cstring(env, new_string);
     free(new_string);
     return;
   }
@@ -940,10 +929,374 @@
     return;
   }
   a=env->head->item->content.val;
+  toss(env); if(env->err) return;
+  
+  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;
+  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;
+  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(environment *env, value *old_value){
+  stackitem *old_item, *new_item, *prev_item;
+
+  value *new_value=new_val(env);
+
+  new_value->type=old_value->type;
+
+  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(env, 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;
+}
+
+/* "dup"; duplicates an item on the stack */
+extern void sx_647570(environment *env) {
+  if((env->head)==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+  push_val(env, copy_val(env, 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;
-  b=env->head->item->content.val;
+
+  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;
-  push_int(&(env->head), a+b);
+
+  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;
+  toss(env); if(env->err) return;
+
+  test= env->head->item;
+  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);
+}
+
+/* "for"; 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;
+  toss(env); if(env->err) return;
+
+  foo= env->head->item;
+  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;
+  }
+}
+
+/* "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= new_val(env);
+  temp_val->content.ptr= env->head;
+  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];
+
+  if(fgets(in_string, 100, env->inputstream)==NULL)
+    push_cstring(env, "");
+  else
+    push_cstring(env, in_string);
+}
+
+/* "read"; Read a value and place on stack */
+extern void sx_72656164(environment *env) {
+  const char symbform[]= "%[a-zA-Z0-9!$%*+./:<=>?@^_~-]%n";
+  const char strform[]= "\"%[^\"]\"%n";
+  const char intform[]= "%i%n";
+  const char blankform[]= "%*[ \t]%n";
+  const char ebrackform[]= "%*1[]]%n";
+  const char semicform[]= "%*1[;]%n";
+  const char bbrackform[]= "%*1[[]%n";
+
+  int itemp, readlength= -1;
+  static int depth= 0;
+  char *match;
+  size_t inlength;
+
+  if(env->in_string==NULL) {
+    if(depth > 0 && env->interactive) {
+      printf("]> ");
+    }
+    readline(env); if(env->err) return;
+
+    if(((char *)(env->head->item->content.ptr))[0]=='\0'){
+      env->err= 4;		/* "" means EOF */
+      return;
+    }
+    
+    env->in_string= malloc(strlen(env->head->item->content.ptr)+1);
+    env->free_string= env->in_string; /* Save the original pointer */
+    strcpy(env->in_string, env->head->item->content.ptr);
+    toss(env); if(env->err) return;
+  }
+  
+  inlength= strlen(env->in_string)+1;
+  match= malloc(inlength);
+
+  if(sscanf(env->in_string, blankform, &readlength)!=EOF
+     && readlength != -1) {
+    ; 
+  } else if(sscanf(env->in_string, intform, &itemp, &readlength) != EOF
+	    && readlength != -1) {
+    push_int(env, itemp);
+  } else if(sscanf(env->in_string, strform, match, &readlength) != EOF
+	    && readlength != -1) {
+    push_cstring(env, match);
+  } else if(sscanf(env->in_string, symbform, match, &readlength) != EOF
+	    && readlength != -1) {
+    push_sym(env, match);
+  } else if(sscanf(env->in_string, ebrackform, &readlength) != EOF
+	    && readlength != -1) {
+    pack(env); if(env->err) return;
+    if(depth != 0) depth--;
+  } else if(sscanf(env->in_string, semicform, &readlength) != EOF
+	    && readlength != -1) {
+    push_sym(env, ";");
+  } else if(sscanf(env->in_string, bbrackform, &readlength) != EOF
+	    && readlength != -1) {
+    push_sym(env, "[");
+    depth++;
+  } else {
+    free(env->free_string);
+    env->in_string = env->free_string = NULL;
+  }
+  if ( env->in_string != NULL) {
+    env->in_string += readlength;
+  }
+
+  free(match);
+
+  if(depth)
+    return sx_72656164(env);
 }