Added xact_t::count member

This allows reports to access the "whicheth" index of the reported
transaction.  It's used mainly by the --average report, which divides
the running total by this count to get the arithmetic mean.

src/filters.cc

@@ -186,8 +186,13 @@ void calc_xacts::operator()(xact_t& xact)
   try {
     xact_t::xdata_t& xdata(xact.xdata());
 
-    if (last_xact && last_xact->has_xdata())
+    if (last_xact) {
+      assert(last_xact->has_xdata());
       add_or_set_value(xdata.total, last_xact->xdata().total);
+      xdata.count = last_xact->xdata().count + 1;
+    } else {
+      xdata.count = 1;
+    }
 
     xact.add_to_value(xdata.total, amount_expr);
 

src/xact.cc

@@ -182,6 +182,11 @@ namespace {
       return xact.amount;
   }
 
+  value_t get_count(xact_t& xact) {
+    assert(xact.xdata_);
+    return xact.xdata_->count;
+  }
+
   value_t get_account(call_scope_t& scope)
   {
     xact_t& xact(find_scope<xact_t>(scope));
@@ -231,6 +236,8 @@ expr_t::ptr_op_t xact_t::lookup(const string& name)
       return WRAP_FUNCTOR(get_wrapper<&get_code>);
     else if (name == "cost")
       return WRAP_FUNCTOR(get_wrapper<&get_cost>);
+    else if (name == "count")
+      return WRAP_FUNCTOR(get_wrapper<&get_count>);
     else if (name == "calculated")
       return WRAP_FUNCTOR(get_wrapper<&get_is_calculated>);
     break;

src/xact.h

@@ -140,6 +140,7 @@ public:
 #define XACT_EXT_MATCHES    0x80
 
     value_t	total;
+    std::size_t	count;
     value_t	value;
     date_t	date;
     account_t *	account;
@@ -147,12 +148,14 @@ public:
 
     std::list<sort_value_t> sort_values;
 
-    xdata_t() : supports_flags<>(), account(NULL), ptr(NULL) {
+    xdata_t()
+      : supports_flags<>(), count(0), account(NULL), ptr(NULL) {
       TRACE_CTOR(xact_t::xdata_t, "");
     }
     xdata_t(const xdata_t& other)
       : supports_flags<>(other.flags()),
 	total(other.total),
+	count(other.count),
 	value(other.value),
 	date(other.date),
 	account(other.account),