--- stack/stack.c	2002/02/07 23:53:14	1.51
+++ stack/stack.c	2003/08/13 11:58:00	1.135
@@ -1,128 +1,80 @@
-/* printf */
-#include <stdio.h>
-/* EXIT_SUCCESS */
-#include <stdlib.h>
-/* NULL */
-#include <stddef.h>
-/* dlopen, dlsym, dlerror */
-#include <dlfcn.h>
-/* assert */
-#include <assert.h>
-/* strcat */
-#include <string.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 *) */
+/* -*- coding: utf-8; -*- */
+/*
+    stack - an interactive interpreter for a stack-based language
+    Copyright (C) 2002	Mats Alritzson and Teddy Hogeborn
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+    Authors: Mats Alritzson <masse@fukt.bth.se>
+	     Teddy Hogeborn <teddy@fukt.bth.se>
+*/
+
+#include "stack.h"
+
+const char* start_message= "Stack version $Revision: 1.135 $\n\
+Copyright (C) 2002  Mats Alritzson and Teddy Hogeborn\n\
+Stack comes with ABSOLUTELY NO WARRANTY; for details type 'warranty;'.\n\
+This is free software, and you are welcome to redistribute it\n\
+under certain conditions; type 'copying;' for details.\n";
+
 
 /* Initialize a newly created environment */
 void init_env(environment *env)
 {
   int i;
 
-  env->err= 0;
-  env->non_eval_flag= 0;
+  env->gc_limit= 400000;
+  env->gc_count= 0;
+  env->gc_ref= NULL;
+
+  env->head= new_val(env);
   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)
+void printerr(environment *env)
 {
-  stackitem *temp= env->head;
+  char *in_string;
 
-  if((env->head)==NULL) {
-    printerr("Too Few Arguments");
-    env->err=1;
+  switch(env->err) {
+  case 0:
     return;
+  case 1:
+    in_string= "Too Few Arguments";
+    break;
+  case 2:
+    in_string= "Bad Argument Type";
+    break;
+  case 3:
+    in_string= "Unbound Variable";
+    break;
+  default:
+    in_string= "Unknown error";
+    break;
   }
-  
-  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 */
+
+  fprintf(stderr, "\"%s\":\nErr: %s\n", env->errsymb, in_string);
 }
 
+
 /* Returns a pointer to a pointer to an element in the hash table. */
 symbol **hash(hashtbl in_hashtbl, const char *in_string)
 {
@@ -152,105 +104,273 @@
   }
 }
 
-/* Generic push function. */
-void push(stackitem** stack_head, stackitem* in_item)
+
+/* Create new value */
+value* new_val(environment *env)
 {
-  in_item->next= *stack_head;
-  *stack_head= in_item;
+  value *nval= malloc(sizeof(value));
+  stackitem *nitem= malloc(sizeof(stackitem));
+
+  assert(nval != NULL);
+  assert(nitem != NULL);
+
+  nval->content.ptr= NULL;
+  nval->type= empty;
+
+  nitem->item= nval;
+  nitem->next= env->gc_ref;
+
+  env->gc_ref= nitem;
+
+  env->gc_count += sizeof(value);
+  nval->gc.flag.mark= 0;
+  nval->gc.flag.protect= 0;
+
+  return nval;
+}
+
+
+/* Mark values recursively. 
+   Marked values are not collected by the GC. */
+inline void gc_mark(value *val)
+{
+  if(val==NULL || val->gc.flag.mark)
+    return;
+
+  val->gc.flag.mark= 1;
+
+  if(val->type==tcons) {
+    gc_mark(CAR(val));
+    gc_mark(CDR(val));
+  }
 }
 
+
+/* Start GC */
+extern void gc_init(environment *env)
+{
+  stackitem *new_head= NULL, *titem;
+  symbol *tsymb;
+  int i;
+
+  if(env->interactive)
+    printf("Garbage collecting.");
+
+  /* Mark values on stack */
+  gc_mark(env->head);
+
+  if(env->interactive)
+    printf(".");
+
+  /* Mark values in hashtable */
+  for(i= 0; i<HASHTBLSIZE; i++)
+    for(tsymb= env->symbols[i]; tsymb!=NULL; tsymb= tsymb->next)
+      if (tsymb->val != NULL)
+	gc_mark(tsymb->val);
+
+  if(env->interactive)
+    printf(".");
+
+  env->gc_count= 0;
+
+  while(env->gc_ref!=NULL) {	/* Sweep unused values */
+    if(!(env->gc_ref->item->gc.no_gc)){ /* neither mark nor protect */
+
+      /* Remove content */
+      switch(env->gc_ref->item->type){
+      case string:
+	free(env->gc_ref->item->content.string);
+	break;
+      case tcons:
+	free(env->gc_ref->item->content.c);
+	break;
+      case port:
+      case empty:
+      case unknown:
+      case integer:
+      case tfloat:
+      case func:
+      case symb:
+	/* Symbol strings are freed when walking the hash table */
+	break;
+      }
+
+      free(env->gc_ref->item);	/* Remove from gc_ref */
+      titem= env->gc_ref->next;
+      free(env->gc_ref);	/* Remove value */
+      env->gc_ref= titem;
+      continue;
+    }
+
+#ifdef DEBUG
+    printf("Kept value (%p)", env->gc_ref->item);
+    if(env->gc_ref->item->gc.flag.mark)
+      printf(" (marked)");
+    if(env->gc_ref->item->gc.flag.protect)
+      printf(" (protected)");
+    switch(env->gc_ref->item->type){
+    case integer:
+      printf(" integer: %d", env->gc_ref->item->content.i);
+      break;
+    case func:
+      printf(" func: %p", env->gc_ref->item->content.func);
+      break;
+    case symb:
+      printf(" symb: %s", env->gc_ref->item->content.sym->id);
+      break;
+    case tcons:
+      printf(" tcons: %p\t%p", CAR(env->gc_ref->item),
+	     CDR(env->gc_ref->item));
+      break;
+    default:
+      printf(" <unknown %d>", (env->gc_ref->item->type));
+    }
+    printf("\n");
+#endif /* DEBUG */
+
+    /* Keep values */     
+    env->gc_count += sizeof(value);
+    if(env->gc_ref->item->type==string)
+      env->gc_count += strlen(env->gc_ref->item->content.string)+1;
+    
+    titem= env->gc_ref->next;
+    env->gc_ref->next= new_head;
+    new_head= env->gc_ref;
+    new_head->item->gc.flag.mark= 0;
+    env->gc_ref= titem;
+  }
+
+  if (env->gc_limit < env->gc_count*2)
+    env->gc_limit= env->gc_count*2;
+
+  env->gc_ref= new_head;
+
+  if(env->interactive)
+    printf("done (%d bytes still allocated)\n", env->gc_count);
+
+}
+
+
+inline void gc_maybe(environment *env)
+{
+  if(env->gc_count < env->gc_limit)
+    return;
+  else
+    return gc_init(env);
+}
+
+
+/* Protect values from GC */
+void protect(value *val)
+{
+  if(val==NULL || val->gc.flag.protect)
+    return;
+
+  val->gc.flag.protect= 1;
+
+  if(val->type==tcons) {
+    protect(CAR(val));
+    protect(CDR(val));
+  }
+}
+
+
+/* Unprotect values from GC */
+void unprotect(value *val)
+{
+  if(val==NULL || !(val->gc.flag.protect))
+    return;
+
+  val->gc.flag.protect= 0;
+
+  if(val->type==tcons) {
+    unprotect(CAR(val));
+    unprotect(CDR(val));
+  }
+}
+
+
 /* 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);
+  value *new_value= new_val(env);
+
+  new_value->content.c= malloc(sizeof(pair));
+  assert(new_value->content.c!=NULL);
+  env->gc_count += sizeof(pair);
+  new_value->type= tcons;
+  CAR(new_value)= val;
+  CDR(new_value)= env->head;
+  env->head= new_value;
 }
 
-/* Push an integer onto the stack. */
-void push_int(stackitem **stack_head, int in_val) 
+
+/* Push an integer onto the stack */
+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->content.i= in_val;
   new_value->type= integer;
-  new_value->refcount=1;
 
-  push(stack_head, new_item);
+  push_val(env, new_value);
+}
+
+
+/* Push a floating point number onto the stack */
+void push_float(environment *env, float in_val)
+{
+  value *new_value= new_val(env);
+
+  new_value->content.f= in_val;
+  new_value->type= tfloat;
+
+  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);
+  int length= strlen(in_string)+1;
 
-  new_value->content.ptr= malloc(strlen(in_string)+1);
-  strcpy(new_value->content.ptr, in_string);
+  new_value->content.string= malloc(length);
+  assert(new_value != NULL);
+  env->gc_count += length;
+  strcpy(new_value->content.string, 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_str(const char *old_string){
-  char validchars[]
-    ="0123456789abcdef";
+char *mangle_str(const char *old_string)
+{
+  char validchars[]= "0123456789abcdef";
   char *new_string, *current;
 
-  new_string=malloc((strlen(old_string)*2)+4);
+  new_string= malloc((strlen(old_string)*2)+4);
+  assert(new_string != NULL);
   strcpy(new_string, "sx_");	/* Stack eXternal */
-  current=new_string+3;
+  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;
+    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';
+  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_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 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 */
@@ -263,210 +383,257 @@
   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);
+  new_fvalue= 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);
-  new_value->content.ptr= *new_symbol;
+  new_value->content.sym= *new_symbol;
 
   if(*new_symbol==NULL) { /* If symbol was undefined */
 
     /* Create a new symbol */
     (*new_symbol)= malloc(sizeof(symbol));
+    assert((*new_symbol) != NULL);
     (*new_symbol)->val= NULL;	/* undefined value */
     (*new_symbol)->next= NULL;
     (*new_symbol)->id= malloc(strlen(in_string)+1);
+    assert((*new_symbol)->id != NULL);
     strcpy((*new_symbol)->id, in_string);
 
     /* Intern the new symbol in the hash table */
-    new_value->content.ptr= *new_symbol;
+    new_value->content.sym= *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();
+    mangled= mangle_str(in_string); /* mangle the name */
+    funcptr= dlsym(handle, mangled); /* and try to find it */
+
+    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();
+      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->type=func;	/* The new value is a function pointer */
-      new_fvalue->content.ptr=funcptr; /* Store function pointer */
+      new_fvalue->type= func;	/* The new value is a function pointer */
+      new_fvalue->content.func= funcptr; /* Store function pointer */
       (*new_symbol)->val= new_fvalue; /* Bind the symbol to the new
                                          function value */
-      new_fvalue->refcount= 1;
     }
+
+    free(mangled);
   }
-  push(&(env->head), new_item);
-}
 
-/* Print newline. */
-extern void nl()
-{
-  printf("\n");
+  push_val(env, new_value);
 }
 
-/* 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");
+/* Print a value */
+void print_val(environment *env, value *val, int noquote, stackitem *stack, 
+	       FILE *stream)
+{
+  stackitem *titem, *tstack;
+  int depth;
+
+  switch(val->type) {
+  case empty:
+    if(fprintf(stream, "[]") < 0){
+      perror("print_val");
+      env->err= 5;
+      return;
+    }
     break;
-  default:
-    push_sym(env, "unknown");
+  case unknown:
+    if(fprintf(stream, "UNKNOWN") < 0){
+      perror("print_val");
+      env->err= 5;
+      return;
+    }
     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);
+    if(fprintf(stream, "%d", val->content.i) < 0){
+      perror("print_val");
+      env->err= 5;
+      return;
+    }
+    break;
+  case tfloat:
+    if(fprintf(stream, "%f", val->content.f) < 0){
+      perror("print_val");
+      env->err= 5;
+      return;
+    }
     break;
   case string:
-    printf("\"%s\"", (char*)stack_head->item->content.ptr);
+    if(noquote){
+      if(fprintf(stream, "%s", val->content.string) < 0){
+	perror("print_val");
+	env->err= 5;
+	return;
+      }
+    } else {			/* quote */
+      if(fprintf(stream, "\"%s\"", val->content.string) < 0){
+	perror("print_val");
+	env->err= 5;
+	return;
+      }
+    }
     break;
   case symb:
-    printf("%s", ((symbol *)(stack_head->item->content.ptr))->id);
+    if(fprintf(stream, "%s", val->content.sym->id) < 0){
+      perror("print_val");
+      env->err= 5;
+      return;
+    }
     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;
+    if(fprintf(stream, "#<function %p>", val->content.func) < 0){
+      perror("print_val");
+      env->err= 5;
+      return;
     }
-    printf("]");
     break;
-  default:
-    printf("#<unknown %p>", (stack_head->item->content.ptr));
+  case port:
+    if(fprintf(stream, "#<port %p>", val->content.p) < 0){
+      perror("print_val");
+      env->err= 5;
+      return;
+    }
     break;
-  }
-}
+  case tcons:
+    if(fprintf(stream, "[ ") < 0){
+      perror("print_val");
+      env->err= 5;
+      return;
+    }
+    tstack= stack;
 
-extern void print_(environment *env) {
-  if(env->head==NULL) {
-    printerr("Too Few Arguments");
-    env->err=1;
-    return;
-  }
-  print_h(env->head);
-}
+    do {
+      titem=malloc(sizeof(stackitem));
+      assert(titem != NULL);
+      titem->item=val;
+      titem->next=tstack;
+      tstack=titem;		/* Put it on the stack */
+      /* Search a stack of values being printed to see if we are already
+	 printing this value */
+      titem=tstack;
+      depth=0;
+
+      while(titem != NULL && titem->item != CAR(val)){
+	titem=titem->next;
+	depth++;
+      }
 
-/* Prints the top element of the stack and then discards it. */
-extern void print(environment *env)
-{
-  print_(env);
-  if(env->err) return;
-  toss(env);
-}
+      if(titem != NULL){	/* If we found it on the stack, */
+	if(fprintf(stream, "#%d#", depth) < 0){	/* print a depth reference */
+	  perror("print_val");
+	  env->err= 5;
+	  free(titem);
+	  return;
+	}
+      } else {
+	print_val(env, CAR(val), noquote, tstack, stream);
+      }
 
-/* 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();
-}
+      val= CDR(val);
+      switch(val->type){
+      case empty:
+	break;
+      case tcons:
+	/* Search a stack of values being printed to see if we are already
+	   printing this value */
+	titem=tstack;
+	depth=0;
+
+	while(titem != NULL && titem->item != val){
+	  titem=titem->next;
+	  depth++;
+	}
+	if(titem != NULL){	/* If we found it on the stack, */
+	  if(fprintf(stream, " . #%d#", depth) < 0){ /* print a depth reference */
+	    perror("print_val");
+	    env->err= 5;
+	    goto printval_end;
+	  }
+	} else {
+	  if(fprintf(stream, " ") < 0){
+	    perror("print_val");
+	    env->err= 5;
+	    goto printval_end;
+	  }
+	}
+	break;
+      default:
+	if(fprintf(stream, " . ") < 0){	/* Improper list */
+	  perror("print_val");
+	  env->err= 5;
+	  goto printval_end;
+        }
+	print_val(env, val, noquote, tstack, stream);
+      }
+    } while(val->type == tcons && titem == NULL);
 
-/* Prints the stack. */
-extern void printstack(environment *env)
-{
-  if(env->head == NULL) {
-    return;
+  printval_end:
+
+    titem=tstack;
+    while(titem != stack){
+      tstack=titem->next;
+      free(titem);
+      titem=tstack;
+    }
+
+    if(! (env->err)){
+      if(fprintf(stream, " ]") < 0){
+	perror("print_val");
+	env->err= 5;
+      }
+    }
+    break;
   }
-  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;
-  }
+  value *temp= env->head;
 
-  env->head= env->head->next;
-  temp->next= env->head->next;
-  env->head->next= temp;
+  if(check_args(env, unknown, unknown, empty))
+    return printerr(env);
+  
+  env->head= CDR(env->head);
+  CDR(temp)= CDR(env->head);
+  CDR(env->head)= 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;
-  }
+  if(check_args(env, symb, empty))
+    return printerr(env);
 
-  val=((symbol *)(env->head->item->content.ptr))->val;
+  val= CAR(env->head)->content.sym->val;
   if(val == NULL){
-    printerr("Unbound Variable");
-    env->err=3;
-    return;
+    env->err= 3;
+    return printerr(env);
   }
-  toss(env);		/* toss the symbol */
+
+  push_val(env, val);		/* Return the symbol's bound value */
+  swap(env);
   if(env->err) return;
-  push_val(&(env->head), val); /* Return its bound value */
+  env->head= CDR(env->head);
 }
 
-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
@@ -475,475 +642,400 @@
 {
   funcp in_func;
   value* temp_val;
-  stackitem* iterator;
-  char* temp_string;
+  value* iterator;
 
-  if(env->head==NULL) {
-    printerr("Too Few Arguments");
-    env->err=1;
-    return;
-  }
+ eval_start:
+
+  gc_maybe(env);
 
-  switch(env->head->item->type) {
+  if(check_args(env, unknown, empty))
+    return printerr(env);
+
+  switch(CAR(env->head)->type) {
     /* if it's a symbol */
   case symb:
+    env->errsymb= CAR(env->head)->content.sym->id;
     rcl(env);			/* get its contents */
     if(env->err) return;
-    if(env->head->item->type!=symb){ /* don't recurse symbols */
-      eval(env);			/* evaluate the value */
-      return;
+    if(CAR(env->head)->type!=symb){ /* don't recurse symbols */
+      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;
+    in_func= CAR(env->head)->content.func;
+    env->head= CDR(env->head);
+    return in_func((void*)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);
-      if(env->head->item->type==symb
-	&& strcmp(";", ((symbol*)(env->head->item->content.ptr))->id)==0) {
-	toss(env);
-	if(env->err) return;
+  case tcons:
+    temp_val= CAR(env->head);
+    protect(temp_val);
+
+    env->head= CDR(env->head);
+    iterator= temp_val;
+    
+    while(iterator->type != empty) {
+      push_val(env, CAR(iterator));
+      
+     if(CAR(env->head)->type==symb
+	 && CAR(env->head)->content.sym->id[0]==';') {
+	env->head= CDR(env->head);
+	
+	if(CDR(iterator)->type == empty){
+	  goto eval_start;
+	}
 	eval(env);
 	if(env->err) return;
       }
-      iterator= iterator->next;
+      if (CDR(iterator)->type == empty || CDR(iterator)->type == tcons) 
+	iterator= CDR(iterator);
+      else {
+	env->err= 2; /* Improper list */
+	return printerr(env); 
+      }
     }
-    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;
+    unprotect(temp_val);
     return;
-  }
 
-  if(env->head->item->type!=list) {
-    printerr("Bad Argument Type");
-    env->err=2;
+  case empty:
+    env->head= CDR(env->head);
+  case integer:
+  case tfloat:
+  case string:
+  case port:
+  case unknown:
     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);
+/* Internal forget function */
+void forget_sym(symbol **hash_entry)
+{
+  symbol *temp;
 
-  iterator= env->head;
+  temp= *hash_entry;
+  *hash_entry= (*hash_entry)->next;
+  
+  free(temp->id);
+  free(temp);
+}
 
-  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;
+int main(int argc, char **argv)
+{
+  environment myenv;
+  int c;			/* getopt option character */
 
-  temp= malloc(sizeof(stackitem));
-  temp->item= pack;
+#ifdef __linux__
+  mtrace();
+#endif
 
-  push(&(env->head), temp);
-  rev(env);
-}
+  init_env(&myenv);
 
-/* 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;
-    }
+  myenv.interactive = isatty(STDIN_FILENO) && isatty(STDOUT_FILENO);
 
-    /* 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, ";");
+  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);
+    }
+  }
 
-      if(*temp==']') {
-	push_sym(env, "[");
-	pack(env);
-	if(env->non_eval_flag)
-	  env->non_eval_flag--;
-	break;
-      }
+  if(myenv.interactive)
+    puts(start_message);
 
-      if(*temp=='[') {
-	push_sym(env, "[");
-	env->non_eval_flag++;
-	break;
+  while(1) {
+    if(myenv.in_string==NULL) {
+      if (myenv.interactive) {
+	if(myenv.err) {
+	  printf("(error %d)\n", myenv.err);
+	  myenv.err= 0;
+	}
+	printf("\n");
+	printstack(&myenv);
+	printf("> ");
       }
+      myenv.err=0;
+    }
+    readstream(&myenv, myenv.inputstream);
+    if (myenv.err) {		/* EOF or other error */
+      myenv.err=0;
+      quit(&myenv);
+    } else if(myenv.head->type!=empty
+	      && CAR(myenv.head)->type==symb
+	      && CAR(myenv.head)->content.sym->id[0] == ';') {
+      if(myenv.head->type != empty)
+	myenv.head= CDR(myenv.head);
+      eval(&myenv);
+    } else {
+      gc_maybe(&myenv);
     }
-  } while(0);
-
-  free(temp);
-
-  if(convert<2) {
-    free(rest);
-    return;
   }
-   
-  stack_read(env, rest);
-  
-  free(rest);
+  quit(&myenv);
+  return EXIT_FAILURE;
 }
 
-/* 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);
+/* Return copy of a value */
+value *copy_val(environment *env, value *old_value)
+{
+  value *new_value;
 
-  if(env->err)
-    return;
+  if(old_value==NULL)
+    return NULL;
 
-  /* The first list element is the new stack head */
-  new_head= temp= env->head->item->content.ptr;
+  new_value= new_val(env);
+  new_value->type= old_value->type;
 
-  env->head->item->refcount++;
-  toss(env);
+  switch(old_value->type){
+  case tfloat:
+  case integer:
+  case func:
+  case symb:
+  case empty:
+  case unknown:
+  case port:
+    new_value->content= old_value->content;
+    break;
+  case string:
+    new_value->content.string= strdup(old_value->content.string);
+    break;
+  case tcons:
 
-  /* Find the end of the list */
-  while(temp->next!=NULL)
-    temp= temp->next;
+    new_value->content.c= malloc(sizeof(pair));
+    assert(new_value->content.c!=NULL);
+    env->gc_count += sizeof(pair);
 
-  /* Connect the tail of the list with the old stack head */
-  temp->next= env->head;
-  env->head= new_head;		/* ...and voila! */
+    CAR(new_value)= copy_val(env, CAR(old_value)); /* recurse */
+    CDR(new_value)= copy_val(env, CDR(old_value)); /* recurse */
+    break;
+  }
 
+  return new_value;
 }
 
-/* Compares two elements by reference. */
-extern void eq(environment *env)
+
+/* read a line from a stream; used by readline */
+void readlinestream(environment *env, FILE *stream)
 {
-  void *left, *right;
-  int result;
+  char in_string[101];
 
-  if((env->head)==NULL || env->head->next==NULL) {
-    printerr("Too Few Arguments");
-    env->err=1;
-    return;
+  if(fgets(in_string, 100, stream)==NULL) {
+    push_cstring(env, "");
+    if (! feof(stream)){
+      perror("readline");
+      env->err= 5;
+    }
+  } else {
+    push_cstring(env, in_string);
   }
-
-  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)
+
+/* Reverse (flip) a list */
+extern void rev(environment *env)
 {
-  int val;
+  value *old_head, *new_head, *item;
 
-  if((env->head)==NULL) {
-    printerr("Too Few Arguments");
-    env->err=1;
-    return;
-  }
+  if(CAR(env->head)->type==empty)
+    return;			/* Don't reverse an empty list */
 
-  if(env->head->item->type!=integer) {
-    printerr("Bad Argument Type");
-    env->err=2;
-    return;
-  }
+  if(check_args(env, tcons, empty))
+    return printerr(env);
 
-  val= env->head->item->content.val;
-  toss(env);
-  push_int(&(env->head), !val);
+  old_head= CAR(env->head);
+  new_head= new_val(env);
+  while(old_head->type != empty) {
+    item= old_head;
+    old_head= CDR(old_head);
+    CDR(item)= new_head;
+    new_head= item;
+  }
+  CAR(env->head)= new_head;
 }
 
-/* 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)
+/* Make a list. */
+extern void pack(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;
-  }
+  value *iterator, *temp, *ending;
 
-  if(env->head->item->type!=symb) {
-    printerr("Bad Argument Type");
-    env->err=2;
-    return;
-  }
+  ending=new_val(env);
 
-  /* long names are a pain */
-  sym=env->head->item->content.ptr;
+  iterator= env->head;
+  if(iterator->type == empty
+     || (CAR(iterator)->type==symb
+     && CAR(iterator)->content.sym->id[0]=='[')) {
+    temp= ending;
+    if(env->head->type != empty)
+      env->head= CDR(env->head);
+  } else {
+    /* Search for first delimiter */
+    while(CDR(iterator)->type != empty
+	  && (CAR(CDR(iterator))->type!=symb
+	   || CAR(CDR(iterator))->content.sym->id[0]!='['))
+      iterator= CDR(iterator);
+    
+    /* Extract list */
+    temp= env->head;
+    env->head= CDR(iterator);
+    CDR(iterator)= ending;
 
-  /* 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 */
+    if(env->head->type != empty)
+      env->head= CDR(env->head);
+  }
 
-  toss(env); toss(env);
-} 
+  /* Push list */
 
-/* Quit stack. */
-extern void quit(environment *env)
-{
-  exit(EXIT_SUCCESS);
+  push_val(env, temp);
+  rev(env);
 }
 
-/* Clear stack */
-extern void clear(environment *env)
-{
-  while(env->head!=NULL)
-    toss(env);
-}
 
-/* List all defined words */
-extern void words(environment *env)
+/* read from a stream; used by "read" and "readport" */
+void readstream(environment *env, FILE *stream)
 {
-  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;
+  const char symbform[]= "%[a-zA-Z0-9!$%*+./:<=>?@^_~-]%n";
+  const char strform[]= "\"%[^\"]\"%n";
+  const char intform[]= "%i%n";
+  const char fltform[]= "%f%n";
+  const char blankform[]= "%*[ \t]%n";
+  const char ebrackform[]= "]%n";
+  const char semicform[]= ";%n";
+  const char bbrackform[]= "[%n";
+
+  int itemp, readlength= -1;
+  int count= -1;
+  float ftemp;
+  static int depth= 0;
+  char *match;
+  size_t inlength;
+
+  if(env->in_string==NULL) {
+    if(depth > 0 && env->interactive) {
+      printf("]> ");
     }
-  }
-}
-
-/* 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;
+    readlinestream(env, env->inputstream);
+    if(env->err) return;
 
-  if(stack_head==NULL) {
-    printerr("Too Few Arguments");
-    env->err=1;
-    return;
+    if((CAR(env->head)->content.string)[0]=='\0'){
+      env->err= 4;		/* "" means EOF */
+      return;
+    }
+    
+    env->in_string= malloc(strlen(CAR(env->head)->content.string)+1);
+    assert(env->in_string != NULL);
+    env->free_string= env->in_string; /* Save the original pointer */
+    strcpy(env->in_string, CAR(env->head)->content.string);
+    env->head= CDR(env->head);
   }
   
-  if(stack_head->item->type!=symb) {
-    printerr("Bad Argument Type");
-    env->err=2;
-    return;
+  inlength= strlen(env->in_string)+1;
+  match= malloc(inlength);
+  assert(match != NULL);
+
+  if(sscanf(env->in_string, blankform, &readlength) != EOF
+     && readlength != -1) {
+    ; 
+  } else if(sscanf(env->in_string, fltform, &ftemp, &readlength) != EOF
+	    && readlength != -1) {
+    if(sscanf(env->in_string, intform, &itemp, &count) != EOF
+       && count==readlength) {
+      push_int(env, itemp);
+    } else {
+      push_float(env, ftemp);
+    }
+  } else if(sscanf(env->in_string, "\"\"%n", &readlength) != EOF
+	    && readlength != -1) {
+    push_cstring(env, "");
+  } 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;
   }
 
-  sym_id= ((symbol*)(stack_head->item->content.ptr))->id;
-  toss(env);
+  free(match);
 
-  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);
+  if(depth)
+    return readstream(env, env->inputstream);
 }
 
-/* Returns the current error number to the stack */
-extern void errn(environment *env){
-  push_int(&(env->head), env->err);
-}
 
-int main()
+int check_args(environment *env, ...)
 {
-  environment myenv;
-  char in_string[100];
+  va_list ap;
+  enum type_enum mytype;
 
-  init_env(&myenv);
+  value *iter= env->head;
+  int errval= 0;
 
-  printf("okidok\n ");
+  va_start(ap, env);
+  while(1) {
+    mytype= va_arg(ap, enum type_enum);
+    //    fprintf(stderr, "%s\n", env->errsymb); 
 
-  while(fgets(in_string, 100, stdin) != NULL) {
-    stack_read(&myenv, in_string);
-    if(myenv.err) {
-      printf("(error %d) ", myenv.err);
-      myenv.err=0;
+    if(mytype==empty)
+      break;
+    
+    if(iter->type==empty || iter==NULL) {
+      errval= 1;
+      break;
     }
-    printf("okidok\n ");
-  }
-  quit(&myenv);
-  return EXIT_FAILURE;
-}
 
-/* + */
-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(mytype==unknown) {
+      iter=CDR(iter);
+      continue;
+    }
 
-  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;
+    if(CAR(iter)->type!=mytype) {
+      errval= 2;
+      break;
+    }
+
+    iter= CDR(iter);
   }
-  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);
+
+  va_end(ap);
+
+  env->err= errval;
+  return errval;
 }