--- stack/stack.c	2002/03/12 21:05:11	1.107
+++ stack/stack.c	2002/03/14 10:39:11	1.109
@@ -37,6 +37,8 @@
 #include <unistd.h>
 /* EX_NOINPUT, EX_USAGE */
 #include <sysexits.h>
+/* assert */
+#include <assert.h>
 
 #ifdef __linux__
 /* mtrace, muntrace */
@@ -121,6 +123,7 @@
   stackitem *nitem= malloc(sizeof(stackitem));
 
   nval->content.ptr= NULL;
+  nval->type= integer;
 
   nitem->item= nval;
   nitem->next= env->gc_ref;
@@ -258,6 +261,7 @@
   value *new_value= new_val(env);
 
   new_value->content.c= malloc(sizeof(cons));
+  assert(new_value->content.c!=NULL);
   new_value->type= tcons;
   CAR(new_value)= val;
   CDR(new_value)= env->head;
@@ -996,7 +1000,7 @@
   }
 
   if(myenv.interactive) {
-    printf("Stack version $Revision: 1.107 $\n\
+    printf("Stack version $Revision: 1.109 $\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\
@@ -1263,7 +1267,6 @@
 
   protect(old_value);
   new_value= new_val(env);
-  protect(new_value);
   new_value->type= old_value->type;
 
   switch(old_value->type){
@@ -1278,15 +1281,16 @@
       strdup((char *)(old_value->content.ptr));
     break;
   case tcons:
-    new_value= NULL;
 
     new_value->content.c= malloc(sizeof(cons));
+    assert(new_value->content.c!=NULL);
+
     CAR(new_value)= copy_val(env, CAR(old_value)); /* recurse */
     CDR(new_value)= copy_val(env, CDR(old_value)); /* recurse */
     break;
   }
 
-  unprotect(old_value); unprotect(new_value);
+  unprotect(old_value);
 
   return new_value;
 }
@@ -1372,7 +1376,30 @@
 extern void sx_656c7365(environment *env)
 {
   if(env->head==NULL || CDR(env->head)==NULL 
-     || CDR(CDR(env->head))==NULL || CDR(CDR(CDR(env->head)))==NULL) {
+     || CDR(CDR(env->head))==NULL || CDR(CDR(CDR(env->head)))==NULL
+     || CDR(CDR(CDR(CDR(env->head))))==NULL) {
+    printerr("Too Few Arguments");
+    env->err= 1;
+    return;
+  }
+
+  if(CAR(CDR(env->head))->type!=symb
+     || strcmp(CAR(CDR(env->head))->content.sym->id, "then")!=0
+     || CAR(CDR(CDR(CDR(env->head))))->type!=symb
+     || strcmp(CAR(CDR(CDR(CDR(env->head))))->content.sym->id, "if")!=0) {
+    printerr("Bad Argument Type");
+    env->err= 2;
+    return;
+  }
+
+  swap(env); toss(env); rot(env); toss(env);
+  ifelse(env);
+}
+
+extern void then(environment *env)
+{
+  if(env->head==NULL || CDR(env->head)==NULL
+     || CDR(CDR(env->head))==NULL) { 
     printerr("Too Few Arguments");
     env->err= 1;
     return;
@@ -1386,7 +1413,7 @@
   }
 
   swap(env); toss(env);
-  ifelse(env);
+  sx_6966(env);
 }
 
 /* "while" */