| Home | Libraries | People | FAQ | More

## 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.

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

Returns: | The result of this function must be assigned to a variable of type `boost::contract::check` declared explicitly (i.e., without using C++11 `auto` declarations) and locally just before the code of the function body (otherwise this library will generate a run-time error, see `BOOST_CONTRACT_ON_MISSING_CHECK_DECL`).