CODEWITHSUNDEEP
c++visual-studio-2012code-generation
Alex O
Alex O

Reputation: 1876

Generating c++ classes without a precompiler

One of our projects involves generating boilerplate code for classes.

For example, given a text file with multiple definitions like:

STRUCT Foo
{
    int i;
    float f;
    string s;
}

a Perl script will create a header file with multiple declarations like:

struct Type_Foo : BaseType
{
    int i;
    float f;
    string s;

    Generated_Foo();
    void clear();
    bool equals(Generated_Foo const&) const;
    string const* toTraceString() const;
    string const* toXmlString() const;
    string const* toJsonString() const;
    bool fromXmlString(char const*);
    bool fromJsonString(char const*);
};

and a corresponding cpp file with the implementations.

My question is:

Is it possible to achieve a similar result (modulo syntax differences) without the precompiler stage?

Thank you!

Upvotes: 1

Views: 69

Answers (1)

Josh Kelley
Josh Kelley

Reputation: 58402

Boost.Preprocessor can do this, just by (ab)using the C/C++ preprocessor. It could look something like this.

#include <boost/preprocessor/seq/for_each.hpp>

#define STRUCT_MEMBER(r, data, elem) elem;

#define STRUCT(structname, seq) \
    struct Type_ ## structname : BaseType { \
        BOOST_PP_SEQ_FOR_EACH(STRUCT_MEMBER, _, seq) \
        Generated_ ## structname(); \
        void clear(); \
        bool equals(Generated_Foo const&) const; \
        string const* toTraceString() const; \
        string const* toXmlString() const; \
        string const* toJsonString() const; \
        bool fromXmlString(char const*); \
        bool fromJsonString(char const*); \
    }

STRUCT(Foo, (int i)(float f)(string s));

Having worked with Boost.Preprocessor, my opinion is that, although it's very cool and can be useful to do everything within C++, it can quickly get complicated for nontrivial uses. If you already have a good, working external code generator (like your Perl scripts), there's nothing wrong with continuing to use it.

Upvotes: 1

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