From 483eb2f56657e8e7f419ab1a4fab8dce9ade8609 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sat, 27 Apr 2024 20:24:20 +0200
Subject: Adding upstream version 14.2.21.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 .../contract/example/features/friend_invariant.cpp | 59 ++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 src/boost/libs/contract/example/features/friend_invariant.cpp

(limited to 'src/boost/libs/contract/example/features/friend_invariant.cpp')

diff --git a/src/boost/libs/contract/example/features/friend_invariant.cpp b/src/boost/libs/contract/example/features/friend_invariant.cpp
new file mode 100644
index 00000000..b9f69bbe
--- /dev/null
+++ b/src/boost/libs/contract/example/features/friend_invariant.cpp
@@ -0,0 +1,59 @@
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract.hpp>
+#include <cassert>
+
+//[friend_invariant
+template<typename T>
+class positive {
+public:
+    void invariant() const {
+        BOOST_CONTRACT_ASSERT(value() > 0);
+    }
+
+    // Can be considered an extension of enclosing class' public interface...
+    friend void swap(positive& object, T& value) {
+        boost::contract::old_ptr<T> old_object_value =
+                BOOST_CONTRACT_OLDOF(object.value());
+        boost::contract::old_ptr<T> old_value = BOOST_CONTRACT_OLDOF(value);
+        // ...so it can be made to check invariants via `public_function`.
+        boost::contract::check c = boost::contract::public_function(&object)
+            .precondition([&] {
+                BOOST_CONTRACT_ASSERT(value > 0);
+            })
+            .postcondition([&] {
+                BOOST_CONTRACT_ASSERT(object.value() == *old_value);
+                BOOST_CONTRACT_ASSERT(value == *old_object_value);
+            })
+        ;
+
+        T saved = object.value_;
+        object.value_ = value;
+        value = saved;
+    }
+    
+private:
+    T value_;
+
+    /* ... */
+//]
+
+public:
+    // Could program contracts for following too.
+    explicit positive(T const& value) : value_(value) {}
+    T value() const { return value_; }
+};
+
+int main() {
+    positive<int> i(123);
+    int x = 456;
+    swap(i, x);
+    assert(i.value() == 456);
+    assert(x == 123);
+    return 0;
+}
+
-- 
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