Function function

boost::contract::function — Program contracts for non-member, private and protected functions.

Synopsis

// In header: <boost/contract/function.hpp>


specify_precondition_old_postcondition_except function();

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.

Returns:

The result of this function must be explicitly assigned to a variable of type boost::contract::check declared locally just before the function body code (otherwise this library will generate a run-time error, see BOOST_CONTRACT_ON_MISSING_CHECK_DECL).

Boost C++ Libraries