--- stack/stack.c	2002/02/07 05:24:19	1.49
+++ stack/stack.c	2002/02/08 03:10:30	1.57
@@ -1,14 +1,12 @@
-/* printf */
+/* printf, sscanf, fgets, fprintf */
 #include <stdio.h>
-/* EXIT_SUCCESS */
+/* exit, EXIT_SUCCESS, malloc, free */
 #include <stdlib.h>
 /* NULL */
 #include <stddef.h>
 /* dlopen, dlsym, dlerror */
 #include <dlfcn.h>
-/* assert */
-#include <assert.h>
-/* strcat */
+/* strcmp, strcpy, strlen, strcat, strdup */
 #include <string.h>
 
 #define HASHTBLSIZE 65536
@@ -50,6 +48,7 @@
 typedef struct stackitem_struct
 {
   value *item;			/* The value on the stack */
+				/* (This is never NULL) */
   struct stackitem_struct *next; /* Next item */
 } stackitem;
 
@@ -101,7 +100,9 @@
       }
       free(val);		/* Free the actual list value */
       break;
-    default:
+    case integer:
+    case func:
+    case symb:
       break;
     }
   }
@@ -198,17 +199,17 @@
 }
 
 /* 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++;
   }
@@ -233,7 +234,7 @@
     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;
@@ -296,7 +297,7 @@
     funcptr= dlsym(handle, in_string); /* Get function pointer */
     dlerr=dlerror();
     if(dlerr != NULL) {		/* If no function was found */
-      mangled=mangle_(in_string);
+      mangled=mangle_str(in_string);
       funcptr= dlsym(handle, mangled); /* try mangling it */
       free(mangled);
       dlerr=dlerror();
@@ -438,6 +439,23 @@
   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)
 {
@@ -541,7 +559,8 @@
     free(temp_string);
     break;
 
-  default:
+  case integer:
+    break;
   }
 }
 
@@ -947,3 +966,125 @@
   if(env->err) return;
   push_int(&(env->head), a+b);
 }
+
+/* Return copy of a value */
+value *copy_val(value *old_value){
+  stackitem *old_item, *new_item, *prev_item;
+
+  value *new_value=malloc(sizeof(value));
+
+  new_value->type=old_value->type;
+  new_value->refcount=0;	/* This is increased if/when this
+				   value is referenced somewhere, like
+				   in a stack item or a variable */
+  switch(old_value->type){
+  case integer:
+    new_value->content.val=old_value->content.val;
+    break;
+  case string:
+    (char *)(new_value->content.ptr)
+      = strdup((char *)(old_value->content.ptr));
+    break;
+  case func:
+  case symb:
+    new_value->content.ptr=old_value->content.ptr;
+    break;
+  case list:
+    new_value->content.ptr=NULL;
+
+    prev_item=NULL;
+    old_item=(stackitem *)(old_value->content.ptr);
+
+    while(old_item != NULL) {	/* While list is not empty */
+      new_item= malloc(sizeof(stackitem));
+      new_item->item=copy_val(old_item->item); /* recurse */
+      new_item->next=NULL;
+      if(prev_item != NULL)	/* If this wasn't the first item */
+	prev_item->next=new_item; /* point the previous item to the
+                                     new item */
+      else
+	new_value->content.ptr=new_item;
+      old_item=old_item->next;
+      prev_item=new_item;
+    }	  
+    break;
+  }
+  return new_value;
+}
+
+/* duplicates an item on the stack */
+extern void dup(environment *env) {
+  if((env->head)==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+  push_val(&(env->head), copy_val(env->head->item));
+}
+
+/* If-Then */
+extern void sx_6966(environment *env) {
+
+  int truth;
+
+  if((env->head)==NULL || env->head->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+
+  if(env->head->next->item->type != integer) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
+  
+  swap(env);
+  if(env->err) return;
+  
+  truth=env->head->item->content.val;
+
+  toss(env);
+  if(env->err) return;
+
+  if(truth)
+    eval(env);
+  else
+    toss(env);
+}
+
+/* If-Then-Else */
+extern void ifelse(environment *env) {
+
+  int truth;
+
+  if((env->head)==NULL || env->head->next==NULL
+     || env->head->next->next==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+
+  if(env->head->next->next->item->type != integer) {
+    printerr("Bad Argument Type");
+    env->err=2;
+    return;
+  }
+  
+  rot(env);
+  if(env->err) return;
+  
+  truth=env->head->item->content.val;
+
+  toss(env);
+  if(env->err) return;
+
+  if(!truth)
+    swap(env);
+  if(env->err) return;
+
+  toss(env);
+  if(env->err) return;
+
+  eval(env);
+}