Make .total constant attribute for Set/Bag/Mix

src/core/Bag.pm

@@ -1,10 +1,13 @@
 my class Bag does Baggy {
+    has Int $!total;
     has $!WHICH;
 
+    submethod total { $!total }
     submethod WHICH { $!WHICH }
     submethod BUILD (:%elems)  {
         my @keys := %elems.keys.sort;
-        $!WHICH = self.^name
+        $!total  := [+] %elems.values.map: {.value};
+        $!WHICH  := self.^name
           ~ '|'
           ~ @keys.map( { $_ ~ '(' ~ %elems{$_}.value ~ ')' } );
         nqp::bindattr(self, Bag, '%!elems', %elems);

src/core/Mix.pm

@@ -1,5 +1,4 @@
 my class Mix does Mixy {
-    has $!WHICH;
 
     method at_key($k --> Real) {
         my $elems := nqp::getattr(self, Mix, '%!elems');

src/core/Set.pm

@@ -1,10 +1,13 @@
 my class Set does Setty {
+    has Int $!total;
     has $!WHICH;
 
+    submethod total { $!total }
     submethod WHICH { $!WHICH }
     submethod BUILD (:%elems) {
         my @keys := %elems.keys.sort;
-        $!WHICH = self.^name ~ '|' ~ @keys.sort;
+        $!total  := %elems.elems;
+        $!WHICH  := self.^name ~ '|' ~ @keys.sort;
         nqp::bindattr(self, Set, '%!elems', %elems);
     }