Re: Released Contract Programming Library for C++
On Jun 10, 4:15 pm, Pavel
<pauldontspamt...@removeyourself.dontspam.yahoo> wrote:
Lorenzo Caminiti wrote:
Hello all,
I have released Contract++ 0.4.0 on SourceForge (this library is being
considered for addition into Boost).
This library implements Contract Programming for the C++ programming
language (see the end of this email). In addition, the library
implements virtual specifiers (final, override, and new, see C++11),
concept checking, and named parameters.
This library is implemented for the C++03 standard and it does not
require C++11.
Documentation:
http://contractpp.svn.sourceforge.net/viewvc/contractpp/releases/cont...
Source:
http://sourceforge.net/projects/contractpp/files/latest/download
Comments are welcome!
Thanks,
--Lorenzo
INTRODUCTION
Contract Programming is also known as Design by Contract(TM) and it
was first introduced by the Eiffel programming language.
All Contract Programming features of the Eiffel programming language
are supported by this library, among others:
* Support for preconditions, postconditions, class invariants, block
invariants, and loop variants.
* Subcontract derived classes (with support for pure virtual functions
and multiple inheritance).
* Access expression old values and function return value in
postconditions.
* Optional compilation and checking of preconditions, postconditions,
class invariants, block invariants, and loop variants.
* Customizable actions on contract assertion failure (terminate by
default but it can throw, exit, etc).
All features:
http://contractpp.svn.sourceforge.net/viewvc/contractpp/releases/cont...
EXAMPLE
The example below shows how to use this library to program contracts
for the STL member function std::vector::push_back (in order to
illustrate subcontracting, the vector class inherits from the somewhat
arbitrary pushable base class).
#include <contract.hpp> // This library.
#include <boost/concept_check.hpp>
#include <vector>
#include "pushable.hpp" // Some base class.
CONTRACT_CLASS(
template( typename T ) requires( boost::CopyConstructible<T> ) =
//
Concepts.
class (vector) extends( public pushable<T> ) // Subcontracting.
) {
CONTRACT_CLASS_INVARIANT_TPL(
empty() == (size() == 0) // More class invarian=
ts here...
)
public: typedef typename std::vector<T>::size_type size_type;
public: typedef typename std::vector<T>::const_reference
const_reference;
CONTRACT_FUNCTION_TPL(
public void (push_back) ( (T const&) value ) override
precondition(
size() < max_size() // More preconditio=
ns here...
)
postcondition(
auto old_size = CONTRACT_OLDOF size()=
, // Old-of
values.
size() == old_size + 1 // More post=
conditions here...
)
) {
vector_.push_back(value); // Original function body.
}
// Rest of class here (possibly with more contracts)...
public: bool empty ( void ) const { return vector_.empty(); }
public: size_type size ( void ) const { return vector_.size(); =
}
public: size_type max_size ( void ) const { return
vector_.max_size(); }
public: const_reference back ( void ) const { return
vector_.back(); }
private: std::vector<T> vector_;
};
NOTES
This library suffers of two limitations:
1. The unusual syntax used to declare classes and functions within the
macros which causes cryptic compiler errors when not used correctly
(syntax error checking and reporting could be somewhat improved in
future revisions of the library but there are fundamental limitations
on what can be done using the preprocessor).
http://contractpp.svn.sourceforge.net/viewvc/contractpp/releases/cont...
2. High compilation times (the authors have not tried to optimize the
library preproprocessor and template meta-programming code yet, that
will be the focus of future releases).
http://contractpp.svn.sourceforge.net/viewvc/contractpp/releases/cont...
This library could be extended to also support concept definitions (at
least for C++11):
http://contractpp.svn.sourceforge.net/viewvc/contractpp/releases/cont...
What does you library do when a precondition or invariant is broken?
When a precondition assertion evaluates to false or its evaluation
throws an exception (i.e., it's broken), the library calls the
precondition broken handler function contract::precondition_broken.
Is it a configurable aspect?
Yes, by default the precondition broken handler function calls
std::terminate. However, programmers can set their own precondition
broken handler function using contract::set_precondition_broken.
Programmer's broken handler functions can exit, abort, throw an
exception, log an error and continue, or anything else programmers
decide to do in their handler functions.
The same is true to postconditions, class invariants, block
invariants, and loop variants.
http://contractpp.svn.sourceforge.net/viewvc/contractpp/releases/contractpp=
_0_4_0/doc/html/contract__/contract_programming_overview.html#contract__.co=
ntract_programming_overview.broken_contracts
If yes, with what granularity (whole app/CONTRACT
CLASS/other) and how is it expressed syntactically?
Granularity and syntax are of set_precondition_broken,
set_postcondition_broken, set_class_invariant_broken_on_entry,
set_class_invariant_broken_on_exit,
set_class_invariant_broken_on_throw, set_block_invariant_broken, and
set_loop_variant_broken. For convenience, set_class_invariant_broken
sets all class invariant broken entry/exit/throw to the same handler.
http://contractpp.svn.sourceforge.net/viewvc/contractpp/releases/contractpp=
_0_4_0/doc/html/contract__/advanced_topics.html#contract__.advanced_topics.=
contract_broken_handlers__throw_on_failure_
Also, at what points are class invariants checked? At entry and exit to a=
nd from
CONTRACT_FUNCTION_TPLs?
Class invariants are checked at public constructor exit (if it doesn't
throw), and public destructor entry, at each non-static public member
function entry and exit (even if it throws). Protected and private
members do not check class invariants. The library also defines static
class invariants and volatile class invariants, these have different
checking semantics.
http://contractpp.svn.sourceforge.net/viewvc/contractpp/releases/contractpp=
_0_4_0/doc/html/contract__/contract_programming_overview.html#contract__.co=
ntract_programming_overview.member_function_calls
Thanks,
--Lorenzo