--- stack/stack.c	2002/02/04 21:47:26	1.28
+++ stack/stack.c	2002/02/07 05:24:19	1.49
@@ -8,6 +8,8 @@
 #include <dlfcn.h>
 /* assert */
 #include <assert.h>
+/* strcat */
+#include <string.h>
 
 #define HASHTBLSIZE 65536
 
@@ -18,8 +20,6 @@
   enum {
     integer,
     string,
-    ref,			/* Reference (to an element in the
-                                   hash table) */
     func,			/* Function pointer */
     symb, 
     list
@@ -58,6 +58,8 @@
 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 */
@@ -67,17 +69,65 @@
 /* Initialize a newly created environment */
 void init_env(environment *env)
 {
-  long i;
+  int i;
 
+  env->err= 0;
+  env->non_eval_flag= 0;
   for(i= 0; i<HASHTBLSIZE; i++)
     env->symbols[i]= NULL;
 }
 
+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 */
+}
+
 /* Returns a pointer to a pointer to an element in the hash table. */
 symbol **hash(hashtbl in_hashtbl, const char *in_string)
 {
-  long i= 0;
-  unsigned long out_hash= 0;
+  int i= 0;
+  unsigned int out_hash= 0;
   char key= '\0';
   symbol **position;
   
@@ -103,15 +153,23 @@
 }
 
 /* Generic push function. */
-int push(stackitem** stack_head, stackitem* in_item)
+void push(stackitem** stack_head, stackitem* in_item)
 {
   in_item->next= *stack_head;
   *stack_head= in_item;
-  return 1;
+}
+
+/* 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. */
-int push_val(stackitem **stack_head, int in_val) 
+void push_int(stackitem **stack_head, int in_val) 
 {
   value *new_value= malloc(sizeof(value));
   stackitem *new_item= malloc(sizeof(stackitem));
@@ -122,11 +180,10 @@
   new_value->refcount=1;
 
   push(stack_head, new_item);
-  return 1;
 }
 
 /* Copy a string onto the stack. */
-int push_cstring(stackitem **stack_head, const char *in_string)
+void push_cstring(stackitem **stack_head, const char *in_string)
 {
   value *new_value= malloc(sizeof(value));
   stackitem *new_item= malloc(sizeof(stackitem));
@@ -138,23 +195,73 @@
   new_value->refcount=1;
 
   push(stack_head, new_item);
-  return 1;
+}
+
+/* Mangle a symbol name to a valid C identifier name */
+char *mangle_(const char *old_string){
+  char validchars[]
+    ="0123456789abcdef";
+  char *new_string, *current;
+
+  new_string=malloc(strlen(old_string)+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+=2;
+    old_string++;
+  }
+  current[0]='\0';
+
+  return new_string;		/* The caller must free() it */
+}
+
+extern void mangle(environment *env){
+  value *new_value;
+  char *new_string;
+
+  if((env->head)==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+
+  if(env->head->item->type!=string) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
+
+  new_string= mangle_((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 a symbol onto the stack. */
-int push_sym(environment *env, const char *in_string)
+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 */
+  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 */
 
   /* Create a new stack item containing a new value */
   new_item= malloc(sizeof(stackitem));
@@ -166,19 +273,20 @@
   new_value->refcount= 1;
 
   /* Look up the symbol name in the hash table */
-  new_value->content.ptr= *hash(env->symbols, in_string);
+  new_symbol= hash(env->symbols, in_string);
+  new_value->content.ptr= *new_symbol;
 
-  if(new_value->content.ptr==NULL) { /* If symbol was undefined */
+  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);
+    (*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;
+    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 */
@@ -186,61 +294,23 @@
       handle= dlopen(NULL, RTLD_LAZY);
 
     funcptr= dlsym(handle, in_string); /* Get function pointer */
-    if(dlerror()==NULL) { 	/* If a function was found */
+    dlerr=dlerror();
+    if(dlerr != NULL) {		/* If no function was found */
+      mangled=mangle_(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_symbol)->val= new_fvalue; /* Bind the symbol to the new
+                                         function value */
       new_fvalue->refcount= 1;
     }
   }
   push(&(env->head), new_item);
-  return 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);
-    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("Stack empty");
-    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. */
@@ -249,15 +319,42 @@
   printf("\n");
 }
 
-/* Prints the top element of the stack. */
-void print_h(stackitem *stack_head)
-{
+/* Gets the type of a value */
+extern void type(environment *env){
+  int typenum;
 
-  if(stack_head==NULL) {
-    printerr("Stack empty");
+  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);
@@ -266,15 +363,34 @@
     printf("\"%s\"", (char*)stack_head->item->content.ptr);
     break;
   case symb:
-    printf("'%s'", ((symbol *)(stack_head->item->content.ptr))->id);
+    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("%p", (funcp)(stack_head->item->content.ptr));
+    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);
 }
 
@@ -282,6 +398,7 @@
 extern void print(environment *env)
 {
   print_(env);
+  if(env->err) return;
   toss(env);
 }
 
@@ -295,17 +412,14 @@
   nl();
 }
 
-
-
 /* Prints the stack. */
 extern void printstack(environment *env)
 {
-  if(env->head != NULL) {
-    print_st(env->head, 1);
-    nl();
-  } else {
-    printerr("Stack empty");
+  if(env->head == NULL) {
+    return;
   }
+  print_st(env->head, 1);
+  nl();
 }
 
 /* Swap the two top elements on the stack. */
@@ -313,13 +427,9 @@
 {
   stackitem *temp= env->head;
   
-  if((env->head)==NULL) {
-    printerr("Stack empty");
-    return;
-  }
-
-  if(env->head->next==NULL) {
-    printerr("Not enough arguments");
+  if(env->head==NULL || env->head->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
   }
 
@@ -328,49 +438,138 @@
   env->head->next= temp;
 } 
 
-stackitem* copy(stackitem* in_item)
+/* Recall a value from a symbol, if bound */
+extern void rcl(environment *env)
 {
-  stackitem *out_item= malloc(sizeof(stackitem));
+  value *val;
 
-  memcpy(out_item, in_item, sizeof(stackitem));
-  out_item->next= NULL;
+  if(env->head == NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
 
-  return out_item;
+  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 */
 }
 
+void stack_read(environment*, char*);
 
-/* If the top element is a reference, determine if it's a reference to a
-   function, and if it is, toss the reference and execute the function. */
+/* 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;
-  stackitem* temp= env->head;
+  value* temp_val;
+  stackitem* iterator;
+  char* temp_string;
 
-  if(temp==NULL) {
-    printerr("Stack empty");
+  if(env->head==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
   }
 
-  if(temp->item->type==symb
-     && ((symbol *)(temp->item->content.ptr))->val != NULL
-     && ((symbol *)(temp->item->content.ptr))->val->type == func) {
-    in_func= (funcp)(((symbol *)(temp->item->content.ptr))->val->content.ptr);
-    toss(env);
+  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;
+    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;
+
+  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(temp->item->type==func) {
-    in_func= (funcp)(temp->item->content.ptr);
-    toss(env); 
-    (*in_func)(env);
+  if(env->head->item->type!=list) {
+    printerr("Bad Argument Type");
+    env->err=2;
     return;
   }
 
-  push(&(env->head), copy(temp));
-  swap(env);
-  toss(env);
+  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. */
@@ -413,21 +612,27 @@
   temp->item= pack;
 
   push(&(env->head), temp);
+  rev(env);
 }
 
 /* Parse input. */
-int stack_read(environment *env, char *in_line) 
+void stack_read(environment *env, char *in_line) 
 {
   char *temp, *rest;
   int itemp;
   size_t inlength= strlen(in_line)+1;
   int convert= 0;
-  static int non_eval_flag= 0;
 
   temp= malloc(inlength);
   rest= malloc(inlength);
 
   do {
+    /* If 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);
@@ -435,7 +640,7 @@
     }
     /* If integer */
     if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
-      push_val(&(env->head), itemp);
+      push_int(&(env->head), itemp);
       break;
     }
     /* Escape ';' with '\' */
@@ -445,14 +650,14 @@
       break;
     } 
     /* If symbol */
-    if((convert= sscanf(in_line, "%[^][ ;\n\r_]%[^\n\r]", temp, rest))) {
+    if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
 	push_sym(env, temp);
 	break;
     }
     /* If single char */
     if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest))) {
       if(*temp==';') {
-	if(!non_eval_flag) {
+	if(!env->non_eval_flag) {
 	  eval(env);		/* Evaluate top element */
 	  break;
 	}
@@ -464,31 +669,29 @@
       if(*temp==']') {
 	push_sym(env, "[");
 	pack(env);
-	if(non_eval_flag!=0)
-	  non_eval_flag--;
+	if(env->non_eval_flag)
+	  env->non_eval_flag--;
 	break;
       }
 
       if(*temp=='[') {
 	push_sym(env, "[");
-	non_eval_flag++;
+	env->non_eval_flag++;
 	break;
       }
     }
   } while(0);
 
-
   free(temp);
 
   if(convert<2) {
     free(rest);
-    return 0;
+    return;
   }
    
   stack_read(env, rest);
   
   free(rest);
-  return 1;
 }
 
 /* Relocate elements of the list on the stack. */
@@ -497,11 +700,22 @@
   stackitem *temp, *new_head;
 
   /* Is top element a list? */
-  if(env->head==NULL || env->head->item->type!=list) {
-    printerr("Stack empty or not 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;
 
@@ -525,7 +739,8 @@
   int result;
 
   if((env->head)==NULL || env->head->next==NULL) {
-    printerr("Not enough elements to compare");
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
   }
 
@@ -535,7 +750,7 @@
   result= (left==right);
   
   toss(env); toss(env);
-  push_val(&(env->head), result);
+  push_int(&(env->head), result);
 }
 
 /* Negates the top element on the stack. */
@@ -543,14 +758,21 @@
 {
   int val;
 
-  if((env->head)==NULL || env->head->item->type!=integer) {
-    printerr("Stack empty or element is not a integer");
+  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_val(&(env->head), !val);
+  push_int(&(env->head), !val);
 }
 
 /* Compares the two top elements on the stack and return 0 if they're the
@@ -567,9 +789,15 @@
   symbol *sym;
 
   /* Needs two values on the stack, the top one must be a symbol */
-  if(env->head==NULL || env->head->next==NULL 
-     || env->head->item->type!=symb) {
-    printerr("Define what?");
+  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;
   }
 
@@ -600,6 +828,59 @@
     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;
@@ -611,8 +892,58 @@
 
   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;
+}
 
-  exit(EXIT_SUCCESS);
+/* + */
+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;
+  }
+
+  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->head), 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;
+  b=env->head->item->content.val;
+  toss(env);
+  if(env->err) return;
+  push_int(&(env->head), a+b);
 }