August 2008 - Boost - lists.preview.boost.org

I need someone with a little-endian system to test an optimization.
by Daryle Walker 19 Aug '08

19 Aug '08

I just added an optimization to some code for systems with octet- sized bytes. I have such a system; so I tested that code. I added a further optimization for little-endian systems. Unfortunately, my computer is big-endian, so I have no way to test the second change. So if you have access to a computer with octet-sized bytes (CHAR_BIT == 8) and larger integers in little-endian format, can you help? The code is on our Subversion server, in the sandbox section, just checked in as revision 48224. Check-out or export the <http:// svn.boost.org/svn/boost/sandbox/md5> directory. The headers are in the "boost" subdirectory, of course. There is one mandatory source file at "libs/coding/src/md5.cpp". There are three test files at "libs/coding/test/md5*test.cpp". Compile all those together with our Unit Test and Serialization libraries. (On my system, I made a project file with a three sub-targets: Boost.Test unit-test, Boost.S11N, and md5.cpp; which the target with the test files compiled linked to.) The "md5.cpp" has the optimized code. The optimized code doesn't activate unless CHAR_BIT is 8 and the file's BOOST_CONTROL_OPTIMIZE_OCTET_BYTES macro is set (or overridden) to 1. The little-endian extra optimization is activated with the BOOST_LITTLE_ENDIAN macro and is mandatory (if valid). I added three now-commented-out #error lines to test which case was activated, which confirmed I'm using a not-little endian system. You can un- comment those to check for yourself. Let me know if the little endian code works, or tell me how to fix it (if not). If you want, you can comment-out the little endian code to test the endian- agnostic code, and then redefine or override BOOST_CONTROL_OPTIMIZE_OCTET_BYTES to be 0 to test the octet-agnostic code (which explodes the packed array into a bool array before combining). Thanks in advance.... -- Daryle Walker Mac, Internet, and Video Game Junkie darylew AT hotmail DOT com

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[Units+Lambda+Math] Functor wrappers for overloaded cmath functions to avoid static_cast in boost::lambda::bind calls
by Torsten Maehne 19 Aug '08

19 Aug '08

Hello, nearly three months ago, I started a thread <http://thread.gmane.org/gmane.comp.lib.boost.devel/175774> on Boost-devel to propose a header, which interfaces Boost.Units with Boost.Lambda. An improved version <boost/units/lambda.hpp> became official part of Boost.Units. However, this header only addresses the mathematical operators (+, -, *, /, ...) and not the common mathematical functions defined cmath (overloaded for boost::units::quantity<Unit, Y> in <boost/units/cmath.hpp>). In an lambda expression, their invocation needs to be postponed till the execution of the whole lambda expression, using boost::lambda::bind to bind the function arguments to the function pointer. The problem is that for overloaded functions, a lengthy static_cast is required to avoid an "unresolved overloaded function type" error as for example in the following code fragment taken from <libs/units/example/lambda.cpp>: using namespace boost::units; using namespace boost::units::si; using boost::function; using boost::lambda::bind; using boost::lambda::_1; function<quantity<current> (quantity<time>) > i = iamp * bind(static_cast<quantity<dimensionless, double> (*)( const quantity<plane_angle>&)>(sin), 2.0 * M_PI * radian * f * _1) + i0; Steven Watanabe proposed in <http://thread.gmane.org/gmane.comp.lib.boost.devel/175774> to create functor wrappers for each cmath function to allow Boost.Lambda to automatically determine the return type of the overloaded functions. As this solution is not Boost.Units specific, he proposed to put the functor wrappers under a more general place like boost::math::functional. I implemented his proposal in the attached header "boost/units/math_functional.hpp" for all the functions overloaded in <boost/units/cmath.hpp>. There is also a unit test "libs/units/test/test_math_functional.cpp" and example "libs/units/examples/math_functional_lambda.cpp". In the latter, the above code snippet simplifies down to: using namespace boost::units; using namespace boost::units::si; using boost::function; using boost::lambda::bind; using boost::lambda::_1; using boost::math::functional; using boost::units::functional; function<quantity<current> (quantity<time>) > i = iamp * bind(sin_t(), 2.0 * M_PI * radian * f * _1) + i0; The functor wrappers include either a sig template or a result_type typedef, which allows Boost::Lambda's bind to choose the correct overloaded function depending on the types passed through the lambda placeholders. The cmath function calls are not prefixed by a namespace qualifier thus allowing argument dependent lookup (ADL, a.k.a. Koenig lookup). All functor wrappers have a '_t' prefix to avoid interference with the ADL. The functor wrappers for functions from <cmath> are defined in namespace boost::math::functional (to anticipate a generalization of this header). Functor wrappers for Boost.Units specific functions are defined in boost::units::functional (for boost::units::pow<long>, boost::units::pow<Rat>, boost::units::root<long>, boost::units::root<Rat>). The implementation has still some issues: * TODO: Functor wrappers for fma, nearbyint, rint (the boost::units implementations are unfinished in trunk). * TODO: Remove limitation of functor wrapper nexttoward to only boost::units::nexttoward, which is currently implemented in terms of boost::math::nextafter because boost::math::nexttoward is not yet available. * Is there a way to organize the code to allow dropping the _t prefix of the functor wrappers so that it would not interfere with the ADL to find the correct overloaded function in the namespaces of the function arguments? The only solution I came up with was by putting using declarations for each function defined in <cmath> and <boost/units/cmath.hpp> in a cmath_ namespace and prefix the function call inside functor wrapper with this namespace, e.g.: namespace cmath_ { using std::sin; using boost::units::sin; } struct sin { template<typename Args> class sig { private: typedef typename boost::tuples::element<1, Args>::type arg1_type; BOOST_TYPEOF_NESTED_TYPEDEF(nested, \ cmath_::sin(typeof_::make<arg1_type>()))) public: typedef typename nested::type type; }; template<typename T> typename sig<typename boost::tuples::tuple<sin, T> >::type operator()(const T& arg) const { return cmath_::sin(arg); } }; However, this has the drawback, that ADL is bypassed and only functions imported into cmath_ are found. * Is there a way to merge the functors for pow<long>, pow<Rat> and root<long>, root<Rat>? Currently, they have rather long names to disambiguate between the template arguments: static_rational_pow_t<Rat>, static_integer_pow_t<long>, static_rational_root_t<Rat>, and static_integer_root_t<long>. I'm looking for comments on this solution, especially, how it can be improved and how it should be restructured to maybe become part of Boost itself. Best regards, Torsten Maehne

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[shifted_ptr] QA
by Phil Bouchard 19 Aug '08

19 Aug '08

Hello, If anybody is able to make shifted_ptr<> break, please share the replication test. It looks to be working fine but the possibility of having something I forgot could still be present. To give everybody a quick idea on the different states both the pointer and the pointee will have are defined as such: shifted_ptr<> (pointer): - part of the pool (local heap) - part of anything else (stack, data, system heap) shifted<> (pointee): - initialized - uninitialized When the shifted<> is initialized it means it knows what "set" it belongs to. If it is uninitialized it means it is still part of a construction sequence that is not yet finalized, hence not yet attached to any "set". Please disregard anything related to shifted_allocator<> because this is of pure shifted_ptr<> concerns. Some test examples can be found at: https://svn.boost.org/svn/boost/sandbox/shifted_ptr/libs/smart_ptr/example/ Regards, -Phil

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Re: [boost] "SuperC"
by Phil Bouchard 19 Aug '08

19 Aug '08

"David Abrahams" <dave(a)boostpro.com> wrote in message news:877iae4oeq.fsf@mcbain.luannocracy.com... [...] >> Let's put it this way. All new "unordered" and multiset containers could >> easily be implemented as: >> 1) superc1st<double, list, vector> s1; >> 2) superc2nd<string, double, map, vector> s2; >> 3) superc2nd<string, double, map, map> s3; > > Sounds reminiscent of boost::graph::adjacency_list. It's a n-th dimensional container as opposed to adjacent_list. All in all we will benefit from: - "unordered" when list is part of the container. Ex.: superc<char, _map<char>, _list> s; - multisets or unordered multisets. Ex.: superc<employee, _map<string>, _map<string>, _map<double>, _map<double>, list> s; - the vector O(1) access when fragmentation is minimal - accessing sorted nodes (using map) but still adjacent in memory (vector). Ex.: superc<char, _map<char>, _vector> s = (_node<_map<char>, _vector> []) {'T', 'h', 'i', 's', ' ', 'i', 's', ' ', 'a', ' ', 't', 'e', 's', 't', '.'}; - interchanging vector iterators to map iterators. Ex.: superc<char, _map<char>, _vector> s; superc<char, _map<char>, _vector>::iterator i = s[10]; // if new _vector<>::operator [] returns: _node<> & s.find(i, s.end()); // O(log n) find from within a range of iterators only - STL code reuse - easy implementation - easy to use -Phil

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[fsm review] Terminal emulator example
by Phil Endecott 19 Aug '08

19 Aug '08

Dear All, Here's another FSM example which I hope is a bit less trivial than the last one. It's for the escape sequence handling in a terminal emulator. If you're curious you can see the real code here: http://svn.anyterm.org/anyterm/trunk/common/Terminal.cc The terminal emulator has to understand: - Normal characters like 'A' that write themselves on the screen at the current cursor position. - Normal control characters like tab, carriage return etc. A peculiar feature is that these characters can occur within escape sequences, where they have their normal effect. - Escape sequences, which consist of ESC followed by one character (normally a letter) and have effects like clearing the screen. - "CSI sequences", which perform more complex operations that may require parameters (e.g. scroll lines N to M up). They have the form ESC [ n1 ; n2 ; n3 ; ... X where the final letter X determines the operation and the number of numeric parameters is variable. So the state machine needs to track whether it is in an escape sequence, in a CSI sequence, or in "normal operation". The transitions are as follows: Current state | Condition | Next state ------------------------------------------------ Normal | ESC | ESC ESC | end of sequence | Normal ESC | [ | CSI ESC | char 26 | Normal CSI | end of sequence | Normal CSI | char 26 | Normal Character 26 explicitly abandons any escape sequence that is in progress. A terminal emulator should behave sensibly when it receives invalid input. One reasonable behaviour on receiving an invalid character is to ignore the preceding incomplete input and to treat the new character as if it had been received in normal mode; or, we could ignore the preceding incomplete input AND the new character and switch to normal mode. The following transitions do something along those lines: Normal | char 26 | Normal ESC | ESC | ESC ESC | invalid sequence | Normal CSI | ESC | ESC CSI | invalid sequence | Normal One thing that we don't want to do is to throw an exception when we get invalid input. My (stripped-down) ad-hoc implementation of this follows: class Terminal { screen_t screen; // basically a 2D array, with some features // for efficient scrolling int cursor_col, cursor_row; int params[MAX_PARAMS]; int nparams; enum state_t { normal, esc, csi }; state_t state; Terminal(): cursor_col(0), cursor_row(0), state(normal) {} void carriage_return() { cursor_col = 0; } void cursor_line_up() { cursor_row--; } void csi_CUU() { cursor_row -= params[0]; } // Lots more functions like those omitted. void write_normal_char(char c) { if (cursor_col>=cols) { cursor_col = 0; cursor_line_down(); } screen(cursor_row,cursor_col) = c; cursor_col++; } void process_char(char c) { // Control chars like tab, newline etc. work even inside // escape sequences: if (c <= 31) { switch (c) { .... case 13: carriage_return(); break; .... case 26: // This code abandons any escape sequence that is in progress state = normal; break; case 27: // Escape state = esc; break; .... } } else { switch (state) { case normal: write_normal_char(c); break; case esc: switch (c) { .... case 'M': cursor_line_up(); state=normal; break; .... case '[': state=csi; nparams=0; break; default: state=normal; break; } break; case csi: if (isdigit(c)) { if (nparams==0) { nparams=1; params[0]=0; } params[nparams-1] = params[nparams-1]*10 + (c-'0'); } else if (c==';') { if (nparams>=MAX_PARAMS) { return; } nparams++; params[nparams-1] = 0; } else { switch (c) { .... case 'A': csi_CUU(); break; .... } state = normal; } } } } }; OK, so let's try to implement that with the proposed library. As before, I haven't tried to compile any of this code: struct Normal; struct Esc; struct CSI; typedef mpl::vector<Normal,Esc,CSI>::type StateList; struct Common { screen_t screen; // BTW, how can I access this from outside? int cursor_col, cursor_row; void carriage_return() { cursor_col = 0; } void handle_control_chars(char c) { switch (c) { .... case 13: carriage_return(); break; .... case 26: // This code abandons any escape sequence that is in progress this->switch_to<Normal>(); break; case 27: // Escape this->switch_to<Esc>(); break; .... } } }; template <typename StateT> struct TermState: fsm::state<StateT,StateList>, virtual Common { // I think I need some using declarations here. Or do they have to be in each of // the derived classes? } struct Normal: TermState<Normal> { void write_normal_char(char c) { if (cursor_col>=cols) { cursor_col = 0; cursor_line_down(); } screen(cursor_row,cursor_col) = c; cursor_col++; } void on_process(const char& c) { if (c<=31) { handle_control_char(c); } else { write_normal_char(c); } } }; struct Esc: TermState<Esc> { void cursor_line_up() { cursor_row--; } void on_process(const char& c) { if (c<=31) { handle_control_char(c); } else { switch (c) { .... case 'M': cursor_line_up(); switch_to<Normal>(); break; .... case '[': switch_to<CSI>(); break; default: switch_to<Normal>(); break; } } } }; struct CSI: TermState<CSI> { int params[MAX_PARAMS]; int nparams; void on_enter() { nparams=0; // doing this here is nice } void csi_CUU() { cursor_row -= params[0]; } void on_process(const char& c) { if (c<=31) { handle_control_char(c); } else { if (isdigit(c)) { if (nparams==0) { nparams=1; params[0]=0; } params[nparams-1] = params[nparams-1]*10 + (c-'0'); } else if (c==';') { if (nparams>=MAX_PARAMS) { return; } nparams++; params[nparams-1] = 0; } else { switch (c) { .... case 'A': csi_CUU(); break; .... } switch_to<Normal>(); } } } }; My view is that the ad-hoc version of the code is sufficiently readable and efficient for my needs, and that the Boost.FSM version does not improve on it. What do other people think? Am I choosing bad examples? If so, please can someone post an example that does demonstrate the library's advantages? (Maybe off-topic, but if any Spirit or Expressive experts would like to show how their libraries would deal with this problem I'd be interested to see that.) Regards, Phil.

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FSM Review Announcement
by Martin Vuille 19 Aug '08

19 Aug '08

The formal review for Andrey Semashev's Finite State Machines (FSM) library is scheduled for August 11th to 20th. Quoting from the documentation: "The main goals of the library are: * Simplicity. It should be very simple to create state machine using this library. * Performance. The state machine infrastructure should not be very time and memory-consuming in order to be applicable in more use cases. * Extensibility. A developer may want to add more states to the existing state machine, and this addition should be relatively safe since it shouldn't interfere with the existing states. The developer should also be able to specify additional transitions and events for the machine with minimum modifications to the existing code." "The following compilers are known to have problems or most likely will have ones: * Microsoft Visual C++ 6.0 and 7.0. Most probably will fail to compile due to lack of partial template specialization support. * Borland C++ Builder 5.5.1 (free version). Fails to compile due to lack of partial template specialization and in-class using declarations support. Some other minor problems also have been noticed. Newer versions of the compiler have not been tested. * OpenWatcom 1.5. Fails to compile due to problems with Boost.MPL code. Newer versions of the compiler have not been tested. * SunPro C++ Compiler 5.5 for Solaris (SPARC). Most likely will show problems with function overload resolution. Newer versions of the compiler have not been tested." The current submission is available from the sandbox vault at http://tinyurl.com/yjozfn (or http://www.boostpro.com/vault/index.php?action=downloadfile&filename=FSM.zip &directory=&PHPSESSID=48493076c1ea60ae316f7b60f15b9ed1, if you prefer.) MV

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[exception] doc error
by Daryle Walker 19 Aug '08

19 Aug '08

[This is based of an unrelated post that mentioned a file in the 1.36 release branch. I just looked and the trunk also has it.] <http://svn.boost.org/svn/boost/trunk/libs/exception/doc/ enable_current_exception.html>, as of revision 47496, has an error in its beginning. It wants T to be a user-defined type so it can derived publicly from it. However, user-defined type doesn't mean class type; it also includes enums, which can't be derived from. -- Daryle Walker Mac, Internet, and Video Game Junkie darylew AT hotmail DOT com

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Can multi-index do this?
by Daryle Walker 19 Aug '08

19 Aug '08

Is it possible for Boost.Multi-index, or anything else in Boost, to make a container that is generally random-access (like vector or deque) but efficiently allows removals anywhere (like list)? -- Daryle Walker Mac, Internet, and Video Game Junkie darylew AT hotmail DOT com

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[Boost.IOStreams] Error with c++ builder 2007
by Sean Farrow 18 Aug '08

18 Aug '08

Hi: When compiling the boost trunk, I get an error that the compiler can't cast 'const mapped_file_sink' to 'const mapped_file &' the line is 474 In libs\iostreams\src\mapped_file.cpp and reads: : mapped_file(static_cast<const mapped_file&>(other)) Anyone got any clue what is happening here? Chers Sean. __________ Information from ESET NOD32 Antivirus, version of virus signature database 3365 (20080818) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com

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Can't use CLR with boost so...
by Jamie Justice 18 Aug '08

18 Aug '08

I need to convert a char array to a byte array of ASCII encoded characters to send over a TCP connection, but I can't use the CLR(and therefore the System namespace) with boost. Does anyone have a solution to this? Thanks, Jamie

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