serialisation about grid

[paboyle]

Found an even better solution via:

http://jhnet.co.uk/articles/cpp_magic
#include
#include
#include "variadic.h"

template
std::ostream & operator << (std::ostream &os,const std::vector & vec) {
os<< "[ "<<vec.size()<< " ] {\n";
for(int i=0;i<vec.size();i++){
os<< "\t"<<vec[i];
if ( i!=vec.size()-1 ) os <<",";
os<<std::endl;
}
os<< "}";
return os;
};
class MyParameters {
public:
GRID_DECL_CLASS_MEMBERS(MyParameters,
int, x1, int, y1, int, z1,
int, x2, int, y2, int, z2,
int, x3, int, y3, int, z3,
int, x4, int, y4, int, z4
);
};

class MyNesting {
public:
GRID_DECL_CLASS_MEMBERS(MyNesting, MyParameters, foo, std::vector, bar);
};

int main(int argc,char **argv)
{
MyNesting boo;
boo.bar.resize(2,13);

boo.foo.x1=1;
boo.foo.y1=2;
boo.foo.z1=3;
boo.foo.x2=5;
boo.foo.y2=6;
boo.foo.z2=7;
boo.foo.x3=8;
boo.foo.y3=10;
boo.foo.z3=11;
boo.foo.x4=13;
boo.foo.y4=14;
boo.foo.z4=15;

std::cout << boo<<std::endl;

}

Gives:

Peters-MacBook-Pro:variadic pab$ ./variadic
class MyNesting {
MyParameters foo = class MyParameters {
int x1 = 1 ;
int y1 = 2 ;
int z1 = 3 ;
int x2 = 5 ;
int y2 = 6 ;
int z2 = 7 ;
int x3 = 8 ;
int y3 = 10 ;
int z3 = 11 ;
int x4 = 13 ;
int y4 = 14 ;
int z4 = 15 ;
} ;
std::vector bar = [ 2 ] {
13,
13
} ;
}

Depends ONLY on variadic CPP macros and a bit of log2 substitutional magic. No dependence on
Boost, or EVEN on C++, let alone tuples and C++11.

When I looked into Hana and Boost.PP they are enumerating cases to hit all "possible" lengths
of variadic macros, so they have no magic. e.g. 64 class members allowed, but 65 is not !?!?

This approach uses a log2 divide and conquer -- 10 macros give 2^10 = 1024 coverage.

The "magic" is as follows:

Peters-MacBook-Pro:variadic pab$ more variadic.h
#ifndef GRID_VARIADIC_H
#define GRID_VARIADIC_H

#define GRID_MACRO_FIRST(a, ...) a
#define GRID_MACRO_SECOND(a, b, ...) b

#define GRID_MACRO_EMPTY()

#define GRID_MACRO_EVAL(...) GRID_MACRO_EVAL1024(VA_ARGS)
#define GRID_MACRO_EVAL1024(...) GRID_MACRO_EVAL512(GRID_MACRO_EVAL512(VA_ARGS))
#define GRID_MACRO_EVAL512(...) GRID_MACRO_EVAL256(GRID_MACRO_EVAL256(VA_ARGS))
#define GRID_MACRO_EVAL256(...) GRID_MACRO_EVAL128(GRID_MACRO_EVAL128(VA_ARGS))
#define GRID_MACRO_EVAL128(...) GRID_MACRO_EVAL64(GRID_MACRO_EVAL64(VA_ARGS))
#define GRID_MACRO_EVAL64(...) GRID_MACRO_EVAL32(GRID_MACRO_EVAL32(VA_ARGS))
#define GRID_MACRO_EVAL32(...) GRID_MACRO_EVAL16(GRID_MACRO_EVAL16(VA_ARGS))
#define GRID_MACRO_EVAL16(...) GRID_MACRO_EVAL8(GRID_MACRO_EVAL8(VA_ARGS))
#define GRID_MACRO_EVAL8(...) GRID_MACRO_EVAL4(GRID_MACRO_EVAL4(VA_ARGS))
#define GRID_MACRO_EVAL4(...) GRID_MACRO_EVAL2(GRID_MACRO_EVAL2(VA_ARGS))
#define GRID_MACRO_EVAL2(...) GRID_MACRO_EVAL1(GRID_MACRO_EVAL1(VA_ARGS))
#define GRID_MACRO_EVAL1(...) VA_ARGS

#define GRID_MACRO_DEFER1(m) m GRID_MACRO_EMPTY()
#define GRID_MACRO_DEFER2(m) m GRID_MACRO_EMPTY GRID_MACRO_EMPTY()()
#define GRID_MACRO_DEFER3(m) m GRID_MACRO_EMPTY GRID_MACRO_EMPTY GRID_MACRO_EMPTY()()()
#define GRID_MACRO_DEFER4(m) m GRID_MACRO_EMPTY GRID_MACRO_EMPTY GRID_MACRO_EMPTY GRID_MACRO_EMPTY()()()()

#define GRID_MACRO_IS_PROBE(...) GRID_MACRO_SECOND(VA_ARGS, 0)
#define GRID_MACRO_PROBE() ~, 1

#define GRID_MACRO_CAT(a,b) a ## b

#define GRID_MACRO_NOT(x) GRID_MACRO_IS_PROBE(GRID_MACRO_CAT(GRID_MACRO_NOT, x))
#define _GRID_MACRO_NOT_0 GRID_MACRO_PROBE()

#define GRID_MACRO_BOOL(x) GRID_MACRO_NOT(GRID_MACRO_NOT(x))

#define GRID_MACRO_IF_ELSE(condition) _GRID_MACRO_IF_ELSE(GRID_MACRO_BOOL(condition))
#define _GRID_MACRO_IF_ELSE(condition) GRID_MACRO_CAT(GRID_MACRO_IF, condition)

#define _GRID_MACRO_IF_1(...) VA_ARGS _GRID_MACRO_IF_1_ELSE
#define _GRID_MACRO_IF_0(...) _GRID_MACRO_IF_0_ELSE

#define _GRID_MACRO_IF_1_ELSE(...)
#define _GRID_MACRO_IF_0_ELSE(...) VA_ARGS

#define GRID_MACRO_HAS_ARGS(...) GRID_MACRO_BOOL(GRID_MACRO_FIRST(GRID_MACRO_END_OF_ARGUMENTS VA_ARGS)())
#define GRID_MACRO_END_OF_ARGUMENTS() 0

#define GRID_MACRO_MAP(m, first, second, ...)
m(first,second)
GRID_MACRO_IF_ELSE(GRID_MACRO_HAS_ARGS(VA_ARGS))(
GRID_MACRO_DEFER4(_GRID_MACRO_MAP)()(m, VA_ARGS)
)(
/* Do nothing, just terminate */
)
#define _GRID_MACRO_MAP() GRID_MACRO_MAP

#define GRID_MACRO_MEMBER(A,B) A B;

#define GRID_MACRO_OS_WRITE_MEMBER(A,B) os<< #A <<" "#B <<" = "<< obj. B <<" ; " <<std::endl;

#define GRID_DECL_CLASS_MEMBERS(cname,...)
GRID_MACRO_EVAL(GRID_MACRO_MAP(GRID_MACRO_MEMBER,VA_ARGS))
friend std::ostream & operator << (std::ostream &os, const cname &obj ) {
os<<"class "<<#cname<<" {"<<std::endl;
GRID_MACRO_EVAL(GRID_MACRO_MAP(GRID_MACRO_OS_WRITE_MEMBER,VA_ARGS))
os<<"}";
return os;
};

#endif

This is pretty cool, because it is, in my view, a complete solution to the problem of struct/object
serialisation in both C and C++ fixing a reflection problem that has persisted for decades, inspired
dozens of IDL "solutions" including the '80's RPC/RPCGEN, '90's CORBA, '00's Apache AVRO etc...

It does not even need C++.

[paboyle]

Closing issue: have committed XMLReader and general Reader/Writer interface along with PugiXML.
It all appears to work nicely with the member list macro working as expected.