Description

This is used to specify preconditions, postconditions, exception guarantees, and old value copies at body for non-member, private and protected functions (these functions never check class invariants, see Function Calls):

void f(...) {
    boost::contract::old_ptr<old_type> old_var;
    boost::contract::check c = boost::contract::function()
        .precondition([&] { // Optional.
            BOOST_CONTRACT_ASSERT(...);
            ...
        })
        .old([&] { // Optional.
            old_var = BOOST_CONTRACT_OLDOF(old_expr);  
            ...
        })
        .postcondition([&] { // Optional.
            BOOST_CONTRACT_ASSERT(...);
            ...
        })
        .except([&] { // Optional.
            BOOST_CONTRACT_ASSERT(...);
            ...
        })
    ;

    ... // Function body.
}

This can be used also to program contracts in implementation code for lambda functions, loops, and arbitrary blocks of code. For optimization, this can be omitted for code that does not have preconditions, postconditions, and exception guarantees.

See Also:

Non-Member Functions, Private and Protected Functions, Lambdas, Loops, Code Blocks