Add LazyPowerSet and LazyKSubsets

[simgrid.git] / src / xbt / utils / iter / LazyKSubsets.hpp

diff --git a/src/xbt/utils/iter/LazyKSubsets.hpp b/src/xbt/utils/iter/LazyKSubsets.hpp
new file mode 100644 (file)
index 0000000..0164e0d
--- /dev/null
+++ b/src/xbt/utils/iter/LazyKSubsets.hpp
@@ -0,0 +1,47 @@
+/* Copyright (c) 2004-2023 The SimGrid Team. All rights reserved.           */
+
+/* This program is free software; you can redistribute it and/or modify it
+ * under the terms of the license (GNU LGPL) which comes with this package. */
+
+#ifndef XBT_UTILS_LAZY_KSUBSETS_HPP
+#define XBT_UTILS_LAZY_KSUBSETS_HPP
+
+#include "src/xbt/utils/iter/subsets.hpp"
+
+namespace simgrid::xbt {
+
+template <class Iterable> class LazyKSubsets<Iterable>;
+template <class Iterable> LazyKSubsets<Iterable> make_k_subsets_iter(unsigned k, const Iterable& container);
+
+/**
+ * @brief A container which "contains" all subsets of
+ * size `k` of some other container `WrapperContainer`
+ *
+ * @note: You should not store instances of this class directly,
+ * as it acts more like a simply wrapping around another iterable
+ * type to make it more convenient to iterate over subsets of
+ * some iterable type.
+ *
+ * @class Iterable: The container from which
+ * the subsets "contained" by this container are derived
+ */
+template <class Iterable> class LazyKSubsets final {
+public:
+  auto begin() const { return subsets_iterator<Iterable::iterator>(k, iterable.begin(), iterable.end()); }
+  auto end() const { return subsets_iterator<Iterable::iterator>(k); }
+
+private:
+  const unsigned k;
+  const Iterable& iterable;
+  LazyKSubsets(unsigned k, const Iterable& iterable) : k(k), iterable(iterable) {}
+  friend LazyKSubsets<Iterable> make_k_subsets_iter(unsigned k, const Iterable& iterable);
+};
+
+template <class Iterable> LazyKSubsets<Iterable> make_k_subsets_iter(unsigned k, const Iterable& container)
+{
+  return LazyKSubsets<Iterable>(k, container);
+}
+
+} // namespace simgrid::xbt
+
+#endif