I am evaluating the use of code generation for my flight simulation project. More specifically there is a requirement to allow "the average engineer" (no offense I am one myself) to define the differential equations that describe the dynamic system in a more natural syntax than C++ provides. The idea is to devise a abstract descriptor language that can be easily understood and edited to generate C++ code from. This descriptor is supplied by the modeling engineer and used by the ones implementing and maintaining the simulation evironment to generate code.

I've got something like this in mind:

model Aircraft has
   state x1, x2;     
   state x3;
   input double : u;
   input bool : flag1, flag2;
   algebraic double : x1x2;
   model Engine : tw1, tw2;
   model Gear : gear;
   model ISA : isa;
   trim routine HorizontalFight;
   trim routine OnGround, General;
   constant double : c1, c2;
   constant int : ci1;
begin differential equations
   x1' = x1 + 2.*x2;
   x2' = x2 + x1x2;
begin algebraic equations
   x1x2 = x1*x2 + x1';
end model

It is important to retain the flexibility of the C language thus the descriptor language is meant to only define certain parts of the definition and implementation of the model class. This way one enigneer provides the model in from of the descriptor language as examplified above and the maintenance enigneer will add all the code to read parameters from files, start/stop/pause the execution of the simulation and how a concrete object gets instatiated.

My first though is to either generate two files from the descriptor file: one .h file containing declarations and one .cpp file containing the implementation of certain functions. These then need to be #included at appropriate places

[File Aircarft.h]

class Aircraft
{
public:
    void Aircraft(..); // hand-written constructor
    void ReadParameters(string &file_name); // hand-written

private:
    /* more hand wirtten boiler-plate code */

    /* generate declarations follow */
    #include "Aircraft.generated.decl" 

};

[File Aircraft.cpp]

Aircarft::Aircraft(..) { /* hand-written constructer implementation */ }

/* more hand-written implementation code */

/* generated implementation code follows */
#include "Aircraft.generated.impl"

Any thoughts or suggestions?