# http://mantis.bearnip.com/view.php?id=477
#
# another fine contribution by fufu. requires 'improve-statistics.patch'

int get_eval_number()
Return the current evaluation number. It's incremented for each top-level call. [...]

The intended purpose of this function is to find out if something has already been done for the current command, heart_beat, call_out or whatever. Control flow in mudlibs is often complicated and adding the necessary infrastructure to a mudlib to answer this question is error-prone and tedious. In the driver it's just a few lines of code.

Index: doc/efun/get_eval_number
===================================================================
--- doc/efun/get_eval_number	(revision 0)
+++ doc/efun/get_eval_number	(revision 0)
@@ -0,0 +1,17 @@
+SYNOPSIS
+        int get_eval_number()
+
+DESCRIPTION
+        Return the current evaluation number. It's incremented for each
+        top-level call. These are: commands, calls to heart_beat, reset,
+        or clean_up, and calls generated by call_out or input_to, master
+        applies triggered by external events, send_erq callbacks and the
+        calls to logon on player login.
+
+        The counter is a 32 bits counter so it can overflow occasionally.
+
+HISTORY
+        Since ldmud 3.3.372
+
+SEE ALSO
+        get_eval_cost()
Index: src/efuns.c
===================================================================
--- src/efuns.c	(revision 2306)
+++ src/efuns.c	(working copy)
@@ -8702,5 +8702,23 @@
     return sp;
 } /* f_utime() */
 
+/*-------------------------------------------------------------------------*/
+svalue_t *
+f_get_eval_number (svalue_t *sp)
+
+/* EFUN get_eval_number()
+ *
+ * Return the current evaluation number. It's incremented for each
+ * top-level call. These are: commands, calls to heart_beat, reset,
+ * or clean_up, and calls generated by call_out or input_to.
+ *
+ * The counter is a 32 bits counter so it will overflow occasionally.
+ */
+
+{
+    push_number(sp, eval_number);
+    return sp;
+} /* f_get_eval_number */
+
 /***************************************************************************/
 
Index: src/func_spec
===================================================================
--- src/func_spec	(revision 2306)
+++ src/func_spec	(working copy)
@@ -772,6 +772,7 @@
 int     set_is_wizard(object, int default: F_CONST1);
 #endif
 
+int     get_eval_number();
 
         /* Obsolete and deprecated functions */
 
Index: src/interpret.c
===================================================================
--- src/interpret.c	(revision 2306)
+++ src/interpret.c	(working copy)
@@ -697,7 +697,8 @@
 
 #endif
 
-       unsigned long total_evalcost;
+unsigned long eval_number; /* evaluation number. 32 bits - will overflow */
+unsigned long total_evalcost;
 static struct timeval eval_begin;
   /* Current total evalcost counter, and start of the evaluation.
    */
@@ -772,6 +773,7 @@
  */
 
 {
+    eval_number++;
     total_evalcost = 0;
     if (gettimeofday(&eval_begin, NULL))
     {
Index: src/interpret.h
===================================================================
--- src/interpret.h	(revision 2306)
+++ src/interpret.h	(working copy)
@@ -116,6 +116,7 @@
 extern p_int apply_cache_miss;
 #endif
 
+extern unsigned long eval_number;
 extern unsigned long total_evalcost;
 extern unsigned long last_total_evalcost;
 extern struct timeval last_eval_duration;