April 2006 - Boost-users - lists.preview.boost.org

Equation idea (follow-up)
by Stephen Gross 05 Apr '06

05 Apr '06

Ok, at least one person said they were interested in seeing my idea for an equation toolkit, so here goes... The files a few hundred lines, so hopefully that's ok for this group. If I've exceed some message size, I'm sorry in advance... ======== e.cpp (client code) follows ========= #include "equation.h" #include "equation_enable_macros.h" int main() { equation::Equation a; a = _y + _z; std::cout << a(_y is 5, _z is 10) << std::endl; a = _x + 8 * (_y - _z); std::cout << a(_x is 2, _y is 3, _z is -9000.9) << std::endl; return 0; } ======== equation.h follows (the real work) ========= // Copyright Stephen Gross 2006 #ifndef api_equation #define api_equation #include <string> #include <iostream> #include <map> #include "boost/function.hpp" #include "boost/lambda/lambda.hpp" #include "boost/lambda/bind.hpp" namespace equation { class ArgTable { typedef std::map<std::string, double> MapType; public: ArgTable & setArg(const std::string & name, double val) { my_map[name] = val; return *this; } virtual double getArg (const std::string & name) const { MapType::const_iterator f = my_map.find(name); if(f == my_map.end()) { std::cout << "Error: Equation requested argument '" << name << "' which was not given." << std::endl; exit(0); } else { return f->second; } } private: MapType my_map; }; class ArgTableReporter : public ArgTable { public: virtual double getArg(const std::string & name) const { my_last_var = name; return 0; } const std::string & getLastVar() const { return my_last_var; } private: mutable std::string my_last_var; }; /// /// Represents an Equation, simply put. /// /// The idea here is that, for any Equation that takes named arguments ("x", "y", etc.) and manipulates them /// arithmetically, such an Equation can in fact be encapsulated in an Equation instance. /// /// class Equation { public: typedef boost::function1<double, const ArgTable &> FunctorType; /// @name Constructors //@{ Equation() : my_ftr(boost::lambda::constant(0)) { ; } Equation(const Equation & other) : my_ftr(other.my_ftr) { } template<typename T> Equation(const T & t) : my_ftr(t) { } //@} /// @name The underlying function that invokes the functor: //@{ double go (const ArgTable & args) const { return my_ftr(args); } //@} /// @name operator() //@{ double operator() () { return go(ArgTable()); } template<typename A1> double operator() (const A1 & a1, double v1) const { ArgTable args; ArgTableReporter names; a1(names); args.setArg(names.getLastVar(), v1); return go(args); } template<typename A1, typename A2> double operator() (const A1 & a1, double v1, const A2 & a2, double v2) const { ArgTable args; ArgTableReporter names; a1(names); args.setArg(names.getLastVar(), v1); a2(names); args.setArg(names.getLastVar(), v2); return go(args); } template<typename A1, typename A2, typename A3> double operator() (const A1 & a1, double v1, const A2 & a2, double v2, const A3 & a3, double v3) const { ArgTable args; ArgTableReporter names; a1(names); args.setArg(names.getLastVar(), v1); a2(names); args.setArg(names.getLastVar(), v2); a3(names); args.setArg(names.getLastVar(), v3); return go(args); } template<typename A1, typename A2, typename A3, typename A4> double operator() (const A1 & a1, double v1, const A2 & a2, double v2, const A3 & a3, double v3, const A4 & a4, double v4) const { ArgTable args; ArgTableReporter names; a1(names); args.setArg(names.getLastVar(), v1); a2(names); args.setArg(names.getLastVar(), v2); a3(names); args.setArg(names.getLastVar(), v3); a4(names); args.setArg(names.getLastVar(), v4); return go(args); } //@} private: FunctorType my_ftr; }; namespace Private { class Sigma { public: Sigma() : my_start(0), my_stop(0), my_iter(boost::lambda::constant(0.0)) { } Sigma(double start, double stop, const Equation & eq) : my_start((int)start), my_stop((int)stop), my_iter(eq) { } Sigma(const Sigma & other) : my_start(other.my_start), my_stop(other.my_stop), my_iter(other.my_iter) { } Sigma& operator=(const Sigma & other) { if(this != &other) { my_start = other.my_start; my_stop = other.my_stop; my_iter = other.my_iter; } return *this; } double go (const ArgTable & args) const { ArgTable newargs = args; double result = 0.0; for(int i = my_start; i <= my_stop; ++i) { newargs.setArg("i", (double)i); result += my_iter.go(newargs); } return result; } private: int my_start; int my_stop; Equation my_iter; }; /// /// Helper struct so that unary math functions can be easily macro-ified for constructing Equations. struct UnaryFunc { UnaryFunc(double (*fn) (double), const Equation::FunctorType & arg_getter) : my_fn(fn), my_arg_getter(arg_getter) { } UnaryFunc(double (*fn) (double), double v) : my_fn(fn), my_arg_getter(boost::lambda::constant(v)) { } UnaryFunc(const UnaryFunc & other) : my_fn(other.my_fn), my_arg_getter(other.my_arg_getter) { } UnaryFunc& operator=(const UnaryFunc & other) { if(this != &other) { my_fn = other.my_fn; my_arg_getter = other.my_arg_getter; } return *this; } double go(const ArgTable & args) const { return (*my_fn) (my_arg_getter(args)); } double (*my_fn) (double); Equation::FunctorType my_arg_getter; }; /// /// Helper struct so that binary math functions can be easily macro-ified for construction Equations. struct BinaryFunc { BinaryFunc( double (*fn) (double, double), const Equation::FunctorType & arg1_getter, const Equation::FunctorType & arg2_getter) : my_fn(fn), my_arg1_getter(arg1_getter), my_arg2_getter(arg2_getter) { } BinaryFunc( double (*fn) (double, double), double arg1, const Equation::FunctorType & arg2_getter) : my_fn(fn), my_arg1_getter(boost::lambda::constant(arg1)), my_arg2_getter(arg2_getter) { } BinaryFunc( double (*fn) (double, double), const Equation::FunctorType & arg1_getter, double arg2) : my_fn(fn), my_arg1_getter(arg1_getter), my_arg2_getter(boost::lambda::constant(arg2)) { } BinaryFunc( double (*fn) (double, double), double arg1, double arg2) : my_fn(fn), my_arg1_getter(boost::lambda::constant(arg1)), my_arg2_getter(boost::lambda::constant(arg2)) { } BinaryFunc(const BinaryFunc & other) : my_fn(other.my_fn), my_arg1_getter(other.my_arg1_getter), my_arg2_getter(other.my_arg2_getter) { } BinaryFunc& operator=(const BinaryFunc & other) { if(this != &other) { my_fn = other.my_fn; my_arg1_getter = other.my_arg1_getter; my_arg2_getter = other.my_arg2_getter; } return *this; } double go(const ArgTable & args) const { return (*my_fn) (my_arg1_getter(args), my_arg2_getter(args)); } double (*my_fn) (double, double); Equation::FunctorType my_arg1_getter; Equation::FunctorType my_arg2_getter; }; } // End namespace Private } // End namespace equation #define VAR(name) boost::lambda::bind<double>(&equation::ArgTable::getArg, boost::lambda::_1, std::string(#name)) #define EQ(name) boost::lambda::bind<double>(&equation::Equation::go, &name, boost::lambda::_1) #endif =========== equation_enable_macros.h follows ============ #ifndef api_equation_enable_macros #define api_equation_enable_macros // Disable macros now available: #undef api_equation_disable_macros #define is , #define _a VAR(a) #define _b VAR(b) #define _c VAR(c) #define _d VAR(d) #define _e VAR(e) #define _f VAR(f) #define _g VAR(g) #define _h VAR(h) #define _i VAR(i) #define _j VAR(j) #define _k VAR(k) #define _l VAR(l) #define _m VAR(m) #define _n VAR(n) #define _o VAR(o) #define _p VAR(p) #define _q VAR(q) #define _r VAR(r) #define _s VAR(s) #define _t VAR(t) #define _u VAR(u) #define _v VAR(v) #define _w VAR(w) #define _x VAR(x) #define _y VAR(y) #define _z VAR(z) #define _sigma(start, stop, iter) boost::lambda::bind<double> (&equation::Private::Sigma::go, equation::Private::Sigma (start, stop, iter), boost::lambda::_1) #define _sqrt(x) boost::lambda::bind<double> (&equation::Private::UnaryFunc::go, equation::Private::UnaryFunc (&sqrt, x), boost::lambda::_1) #define _pow(x, y) boost::lambda::bind<double> (&equation::Private::BinaryFunc::go, equation::Private::BinaryFunc (&pow, x, y), boost::lambda::_1) #endif ========= end of code snippets ==============

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Re: [Boost-users] equation (really expression) idea (follow-up)
by james.jones＠firstinvestors.com 05 Apr '06

05 Apr '06

From: "Stephen Gross" <sgross(a)darwin.epbi.cwru.edu> > Ok, at least one person said they were interested in seeing my idea for an > equation toolkit, so here goes... The files a few hundred lines, so > hopefully that's ok for this group. If I've exceed some message size, I'm > sorry in advance... This is a decent start, but I have several problems with it. 1. Types are not template-ized. I don't want everything to be a double. 2. Perhaps variables should be first-class objects, not just placeholders in BLL. 3. (Style not substance) Many of the type and function names aren't very clear. Examples: go() and MapType; I'm thinking the client syntax should be something more like this: expression expr; variable<double> x; variable<int> y; expr = x + y; double v = expr; // would throw because x and y are unassigned x = 10; y = 20; v = expr; // assigns 30 to v It would be cool to then be able to define some sort of 'evaluate' function so that you could write: v = expr.evaluate(10, 20); // v <- 30 Perhaps this is where the BLL comes in, because you'd first have to map the positional arguments to the variables in the expression. Maybe you could also extend this to handle currying. - James

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Problem with memory allocation in UBLAS matrix and vector
by Vasilios Papakos 05 Apr '06

05 Apr '06

Hello, Here is the problem I am having: In the following code (tried to keep it as short as possible), I create a vector [vec1] and a matrix [mat1] in the respective test functions. Then, I create [vec2] and [mat2] in main, but when I print them they have the values of [vec1] and [mat1]. Why is this happening? I am quite new to boost, so I may miss something quite fundamental. I really appreciate you help. System: Fedora Core 4, boost-1.33.1.-5, g++ 4.0.2 Regards, Vasilios ---------------------------------------------------------------------------------------------------------------------------------------------------------- #include <boost/numeric/ublas/vector.hpp> #include <boost/numeric/ublas/matrix.hpp> #include <boost/numeric/ublas/io.hpp> typedef boost::numeric::ublas::matrix<double> ublas_matrix; typedef boost::numeric::ublas::vector<double> ublas_vector; using std::cout; using std::endl; void test_matrix(); void test_vector(); int main() { test_matrix(); ublas_matrix mat2(3, 2); cout << "m2 = " << mat2 << endl; test_vector(); ublas_vector vec2(4); cout << "v2 = " << vec2 << endl; } void test_matrix() { unsigned m = 3, n = 2; ublas_matrix mat1(m, n); for (unsigned i = 0; i < m; ++ i) for (unsigned j = 0; j < n; ++ j) mat1(i, j) = 5.0; } void test_vector() { ublas_vector vec1(4); for (unsigned i = 0; i < vec1.size(); ++i) vec1(i) = i; } ----------------------------------------------------------------------------------------------------------------------------------------------------------

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Serialization: crash at launch of program (due to boost::serialization::base_object)
by RIVASSEAU Jean Noel 05 Apr '06

05 Apr '06

Hello, My program crashes at launch (not even a exit(0) as the first line of main(int argc, char *argv[]) will stop it from crashing), due to the BSL. What I am trying to do is: I have a class, whose serialization is split (eg, save and load functions are provided, and they are different). Now this class had a parent class, so I used to call boost::serialization::base_object<MObject>() on the base class MObject. However I want to change the parent of my class to a different class. I also want to update my old archives, so I decided to leave the load function of my class untouched, while I would change the save function, to update the call to base_object to the new parent class (not MObject anymore). I thought it would work, since it would load the old archive using the same method, but save it using the new, so I would have ran only one time the program and the archive would be updated (then, of course, before running it again I would have to recompile it one more time with the correct changes to the load function). But it does not work as expected, since it seems the BSL does not like the fact that save and load functions calls to boost::serialization::base_object do not specify the same base class. It does not complain at compile time but crashes at run time before even entering main and certainly before loading any archive. The crash is due to a NULL pointer, I have tried to debug with gdb but the crash apparently occurs on the _libkernel32_a_iname () so I do not not know where it is (too low level for me). Robert, do you have an idea what is going on? I suspect a bug - however if it is "normal" behaviour (I think it should then throw an exception rather than crash), do you have an idea how could I update my archives? I need to change the parent of this class, but need to be able to read my old archives - and changing them "by hand" by looking into the XML archive code is tool hard. Thank you, regards Jean-Noël Rivasseau

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Re: [Boost-users] Idea for equation library
by james.jones＠firstinvestors.com 05 Apr '06

05 Apr '06

Stephen Gross wrote: > The idea is that you can encapsulate an algebraic function in a standalone > 'Equation' instance, and dynamically reassign that equation. It's built off > of boost::lambda (of course), but it lets you name the variables rather than > just refer to them with the standard placeholders (_1, _2, etc.). Is it > worthwhile for me to post the toolkit code on this group? I'd love to see this. But it should be called "Expression", not "Equation" - the concepts you'd be creating aren't "equations". Equation: x + y = z Expression: x + y - James

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Confusion on The Directory Structure For serialization library
by Cheok Yan Cheng 05 Apr '06

05 Apr '06

You might thoroughly read http://www.boost.org/more/getting_started.html#Build_Install. Where under the Results section, the naming convention is described. -------------------------------------------------------- That's cool! I get the naming convention I want after running bjam install. Thank you very much! __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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Boost.Filesystem
by Elisha Berns 05 Apr '06

05 Apr '06

I asked this two weeks ago but didn't get any reply: Can file locking and permission setting be added to Boost.Filesystem? Elisha Berns

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Re: [Boost-users] [Serialization] a newbie question about retrieving objects serialized through base class pointers
by t.sammoud 05 Apr '06

05 Apr '06

Robert Ramey wrote: >If BOOST_CLASS_EXPORT is used, the class name is included as an attribute in >the xml file. >Otherwise, the class_id variable - another xml attribute is used. This is >set/recovered by the >"registration" process. I understood from the documentation that BOOST_CLASS_EXPORT works for classes which derive from a virtual base class, which isn't really the case for me. Is it possible to add class names as attributes to xml archives even for classes which aren't serialized through base class pointers? If there is a way, this would really helps me Thanks Accédez au courrier électronique de La Poste : www.laposte.net ; 3615 LAPOSTENET (0,34 /mn) ; tél : 08 92 68 13 50 (0,34/mn)

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bjam build question
by Joe McCay 05 Apr '06

05 Apr '06

Is it possible to specify a clean build from scratch, or do you have manually delete the object files and stuff? jmccay

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'Function String' parser question
by K M 05 Apr '06

05 Apr '06

Hi, I have this parser that parses string that represents a function, (a c++ function prototype to say) CONSIDER: bool parse_info<> x_parser4(char const* str, FunctionSpec& spec) { // some rules... rettype = lexeme_d[ (alpha_p) >> *(alnum_p | space_p | ch_p('*')) ][list_actor(spec)]; // assign function name when match... function = lexeme_d[ (alpha_p | ch_p('_')) >> *(alnum_p | ch_p('_')) ][assign_a(spec.m_Name)]; // other rules.... .... return parse(str,top); } // Here's what my struct looks like: struct FunctionSpec { std::string m_Name; enum eVarType { VAR_VOID, VAR_BOOL, VAR_INT... } eVarType m_RetType; }; In the function rule what i did was just to assign the name to the m_Name of spec In the rettype tule what i did there was to pass the match string along with the struct (spec) to a class (list_actor) using the operator()... Problem is that i can't jsut assign m_RetType to the 'matched string' delivered to list_actor's operator() since this one is an enumerated type; In the code i attached, there is a function that 'maps' a string to eVarType, but i can't call this function within the list_actor's operator() body? i.e. template <typename ActionIterT> operator(...,...) { // can't do here? // tried to bind the function but it didn't work as well... } In summary what i need to do is to assign value for m_RetType and other members of FunctionSpec using the strings i get from parsing, e.g. when i get the string "void" for a match in the rettype rule, m_RetType will be assigned to VAR_VOID. etc. ----- krby

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