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## Function template public_function

boost::contract::public_function — Program contracts for public functions that are not static, not virtual, and do not not override.

## Synopsis

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

    template<typename Class>
      specify_precondition_old_postcondition_except public_function(Class * obj);

## Description

This is used to specify preconditions, postconditions, exception guarantees, old value copies at body, and check class invariants for public functions that are not static, not virtual, and do not override:

    class u {
        friend class boost::contract::access;

        void invariant() const { // Optional (as for static and volatile).
            BOOST_CONTRACT_ASSERT(...);
            ...
        }

    public:
        void f(...) {
            boost::contract::old_ptr<old_type> old_var;
            boost::contract::check c = boost::contract::public_function(this)
                .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.
        }

        ...
    };

For optimization, this can be omitted for public functions that do not have preconditions, postconditions and exception guarantees, within classes that have no invariants.

See Also: Public Functions

Parameters: |
`obj` | The object `this` from the scope of the enclosing public function declaring the contract. This object might be mutable, `const`, `volatile`, or `const volatile` depending on the cv-qualifier of the enclosing function (volatile public functions will check volatile class invariants, see Volatile Public Functions).
Template Parameters: |
`Class` | The type of the class containing the public function declaring the contract. (Usually this template parameter is automatically deduced by C++ and it does not need to be explicitly specified by programmers.)
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 public function body (otherwise this library will generate a run-time error, see `BOOST_CONTRACT_ON_MISSING_CHECK_DECL`).