How to define a variant record type in C

Dear Sir or Madam:
I am looking for help to define a variant record type in C. I am trying to map a Ada variant record data type into C data type, but I really dont know how to convert it into C. Here is the code
in Ada

Code:

---

type POWER is (GAS, STEAM, DIESEL, NONE);

  type VEHICLE (Engine : POWER) is
      record
        Model_Year : INTEGER range 1888..1992;
        Wheels    : INTEGER range 2..18;
        case Engine is
            when GAS    => Cylinders  : INTEGER range 1..16;
            when STEAM  => Boiler_Size : INTEGER range 5..22;
                          Coal_Burner : BOOLEAN;
            when DIESEL => Fuel_Inject : BOOLEAN;
            when NONE  => Speeds      : INTEGER range 1..15;
        end case;
      end record;

  Ford    : VEHICLE(GAS);
  Truck  : VEHICLE(DIESEL);
  Schwinn : VEHICLE(NONE);
  Stanley : VEHICLE(STEAM);

---

Any C code example or explaining how to define this kind of data structure in C is greatly appreciated.

DiepVien_007

Use C++ and build a class. Or, use C and enums. You cannot enforce the behaviour you want in C easily. Yes it can be done. No, it's not easy. Use C++.
[edit]

Code:

---

/* type POWER is (GAS, STEAM, DIESEL, NONE); */
typedef enum { NONE, GAS, STEAM, DIESEL } POWER;

/*
  type VEHICLE (Engine : POWER) is
      record
        Model_Year : INTEGER range 1888..1992;
        Wheels    : INTEGER range 2..18;
        case Engine is
            when GAS    => Cylinders  : INTEGER range 1..16;
            when STEAM  => Boiler_Size : INTEGER range 5..22;
                          Coal_Burner : BOOLEAN;
            when DIESEL => Fuel_Inject : BOOLEAN;
            when NONE  => Speeds      : INTEGER range 1..15;
        end case;
      end record;
*/
typedef struct {
        unsigned char Model_Year;
        unsigned char Wheels;
        POWER Type;
        union
        {
                struct
                {
                        unsigned char Cylinders;
                } Gas;
                struct
                {
                        unsigned char Boiler_Size;
                        unsigned char Coal_Burner;
                } Steam;
                struct
                {
                        unsigned char Fuel_Inject;
                } Diesel;
                struct
                {
                        unsigned char Speeds;
                }
        } Engine;
} VEHICLE;

/*  Ford    : VEHICLE(GAS); */
VEHICLE Ford;

SetWheels( &Ford, 4 ); /* This would assign the value. */
SetYear( &Ford, 1983 ); /* This would assign the value. */
SetEngine( &Ford, GAS ); /* This would prompt for the correct values. */

---

It is up to you to enforce the values correctly. You really want C++.
[/edit]

Quzah.

Thanks alot quazz.
Yup! I think I better convert all Ada variant record types into
C++ classes, such as class VEHICLE.....

DiepVien_007