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Diffstat (limited to 'src/boost/libs/contract/example/n1962/factorial.cpp')
-rw-r--r-- | src/boost/libs/contract/example/n1962/factorial.cpp | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/src/boost/libs/contract/example/n1962/factorial.cpp b/src/boost/libs/contract/example/n1962/factorial.cpp new file mode 100644 index 00000000..98f12a38 --- /dev/null +++ b/src/boost/libs/contract/example/n1962/factorial.cpp @@ -0,0 +1,39 @@ + +// 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 + +//[n1962_factorial +#include <boost/contract.hpp> +#include <cassert> + +int factorial(int n) { + int result; + boost::contract::check c = boost::contract::function() + .precondition([&] { + BOOST_CONTRACT_ASSERT(n >= 0); // Non-negative natural number. + BOOST_CONTRACT_ASSERT(n <= 12); // Max function input. + }) + .postcondition([&] { + BOOST_CONTRACT_ASSERT(result >= 1); + if(n < 2) { // Select assertion. + BOOST_CONTRACT_ASSERT(result == 1); + } else { + // Assertions automatically disabled in other assertions. + // Therefore, this postcondition can recursively call the + // function without causing infinite recursion. + BOOST_CONTRACT_ASSERT_AUDIT(n * factorial(n - 1)); + } + }) + ; + + return n < 2 ? (result = 1) : (result = n * factorial(n - 1)); +} + +int main() { + assert(factorial(4) == 24); + return 0; +} +//] + |