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perl/Examples/Chap7/FlatDB_Ovl.pm

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+
+
+###
+### FlatDB_Overloaded.pm
+###
+
+## Chapter 7 section 4.1
+
+package FlatDB_Overloaded;
+BEGIN {
+  for my $f (qw(and or without)) {
+    *{"query_$f"} = \&{"FlatDB_Composable::query_$f"};
+  }
+}
+use base 'FlatDB_Composable';
+
+sub query {
+  $self = shift;
+  my $q = $self->SUPER::query(@_);
+  bless $q => __PACKAGE__;
+}
+
+sub callbackquery {
+  $self = shift;
+  my $q = $self->SUPER::callbackquery(@_);
+  bless $q => __PACKAGE__;
+}
+
+1;
+
+
+## Chapter 7 section 4.1
+
+use overload '|' => \&query_or,
+             '&' => \&query_and,
+             '-' => \&query_without,
+             'fallback' => 1;