--- stack/stack.c	2002/02/05 22:25:04	1.31
+++ stack/stack.c	2002/02/06 00:52:31	1.36
@@ -18,8 +18,6 @@
   enum {
     integer,
     string,
-    ref,			/* Reference (to an element in the
-                                   hash table) */
     func,			/* Function pointer */
     symb, 
     list
@@ -58,6 +56,7 @@
 typedef struct {
   stackitem *head;		/* Head of the stack */
   hashtbl symbols;		/* Hash table of all variable bindings */
+  int err;			/* Error flag */
 } environment;
 
 /* A type for pointers to external functions */
@@ -69,6 +68,7 @@
 {
   long i;
 
+  env->err=0;
   for(i= 0; i<HASHTBLSIZE; i++)
     env->symbols[i]= NULL;
 }
@@ -103,11 +103,10 @@
 }
 
 /* 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 */
@@ -120,7 +119,7 @@
 }
 
 /* Push an integer onto the stack. */
-int push_int(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));
@@ -131,11 +130,10 @@
   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));
@@ -147,11 +145,10 @@
   new_value->refcount=1;
 
   push(stack_head, new_item);
-  return 1;
 }
 
 /* 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... */
@@ -206,7 +203,6 @@
     }
   }
   push(&(env->head), new_item);
-  return 1;
 }
 
 void printerr(const char* in_string) {
@@ -244,7 +240,8 @@
   stackitem *temp= env->head;
 
   if((env->head)==NULL) {
-    printerr("Stack empty");
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
   }
   
@@ -262,12 +259,6 @@
 /* Prints the top element of the stack. */
 void print_h(stackitem *stack_head)
 {
-
-  if(stack_head==NULL) {
-    printerr("Stack empty");
-    return;
-  }
-
   switch(stack_head->item->type) {
   case integer:
     printf("%d", stack_head->item->content.val);
@@ -278,13 +269,24 @@
   case symb:
     printf("'%s'", ((symbol *)(stack_head->item->content.ptr))->id);
     break;
+  case func:
+    printf("#<function %p>", (funcp)(stack_head->item->content.ptr));
+    break;
+  case list:
+    printf("#<list %p>", (funcp)(stack_head->item->content.ptr));
+    break;
   default:
-    printf("%p", (funcp)(stack_head->item->content.ptr));
+    printf("#<unknown %p>", (funcp)(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);
 }
 
@@ -292,6 +294,7 @@
 extern void print(environment *env)
 {
   print_(env);
+  if(env->err) return;
   toss(env);
 }
 
@@ -310,12 +313,13 @@
 /* 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) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
   }
+  print_st(env->head, 1);
+  nl();
 }
 
 /* Swap the two top elements on the stack. */
@@ -324,12 +328,14 @@
   stackitem *temp= env->head;
   
   if((env->head)==NULL) {
-    printerr("Stack empty");
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
   }
 
   if(env->head->next==NULL) {
-    printerr("Not enough arguments");
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
   }
 
@@ -348,21 +354,31 @@
   return out_item;
 }
 
+/* Recall a value from a symbol, if bound */
 extern void rcl(environment *env)
 {
   value *val;
 
   if(env->head == NULL) {
-    printerr("Stack empty");
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
   }
 
   if(env->head->item->type!=symb) {
-    printerr("Not a symbol");
+    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 */
 }
 
@@ -372,32 +388,20 @@
 extern void eval(environment *env)
 {
   funcp in_func;
-  value* val;
   if(env->head==NULL) {
-    printerr("Stack empty");
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
   }
 
   /* if it's a symbol */
   if(env->head->item->type==symb) {
 
-    /* If it's not bound to anything */
-    if (((symbol *)(env->head->item->content.ptr))->val == NULL) {
-      printerr("Unbound variable");
-      return;
-    }
-    
-    /* If it contains a function */
-    if (((symbol *)(env->head->item->content.ptr))->val->type == func) {
-      in_func=
-	(funcp)(((symbol *)(env->head->item->content.ptr))->val->content.ptr);
-      toss(env);
-      (*in_func)(env);		/* Run the function */
+    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;
-    } else {			/* If it's not a function */
-      val=((symbol *)(env->head->item->content.ptr))->val;
-      toss(env);		/* toss the symbol */
-      push_val(&(env->head), val); /* Return its bound value */
     }
   }
 
@@ -405,10 +409,9 @@
   if(env->head->item->type==func) {
     in_func= (funcp)(env->head->item->content.ptr);
     toss(env); 
+    if(env->err) return;
     (*in_func)(env);
-    return;
   }
-
 }
 
 /* Make a list. */
@@ -483,7 +486,7 @@
       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;
     }
@@ -535,8 +538,14 @@
   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;
   }
 
@@ -563,7 +572,8 @@
   int result;
 
   if((env->head)==NULL || env->head->next==NULL) {
-    printerr("Not enough elements to compare");
+    printerr("Too Few Arguments");
+    env->err=1;
     return;
   }
 
@@ -581,8 +591,15 @@
 {
   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;
   }
 
@@ -605,9 +622,15 @@
   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;
   }
 
@@ -638,6 +661,59 @@
     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;
@@ -649,6 +725,10 @@
 
   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 ");
   }