How to define a define that defines some defines ?

[theotyflos]

Hi all,

I have the following:

/*--- SNIP ---*/

typedef struct Argument_s
{
char *address;
int type;
int length;
} ARGUMENT;

#define Function(F) int F( int ArgCount, ARGUMENT ArgVector[] )

#define First ArgVector[0]
#define First_A First.address
#define First_T First.type
#define First_L First.length
#define Second ArgVector[1]
#define Second_A Second.address
#define Second_T Second.type
#define Second_L Second.length
#define Third ArgVector[2]
#define Third_A Third.address
#define Third_T Third.type
#define Third_L Third.length

Function(One)
{
/* do something with First_A */
/* do something with First_T */
/* do something with First_L */
/* do something with Second_A */
/* do something with Second_T */
/* do something with Second_L */
/* do something with Third_A */
/* do something with Third_T */
/* do something with Third_L */
/* etc etc */
}

#define Apple ArgVector[0]
#define Apple_A Apple.address
#define Apple_T Apple.type
#define Apple_L Apple.length
#define Orange ArgVector[1]
#define Orange_A Orange.address
#define Orange_T Orange.type
#define Orange_L Orange.length

Function(Two)
{
/* do something with Apple_A */
/* do something with Apple_T */
/* do something with Apple_L */
/* do something with Orange_A */
/* do something with Orange_T */
/* do something with Orange_L */
/* etc etc */
}

/*--- SNIP ---*/

The question is: Is there a way instead of writing all those #defines
for the arguments (First, Second, etc), to write something like:

#define Arg(n) #define Arg ArgVector[n] \
#define Arg##_A Arg.address \
#define Arg##_T Arg.type \
#define Arg##_L Arg.length

and define the arguments like this:

Arg First(0)
Arg Second(1)
Arg Third(2)
Function(One)
.....
Arg Apple(0)
Arg Orange(1)
Function(Two)
.....


Thanks in advance everyone.

 

[Joona I Palaste]

typedef struct Argument_s
{
char *address;
int type;
int length;
} ARGUMENT;

#define Function(F) int F( int ArgCount, ARGUMENT ArgVector[] )

#define First ArgVector[0]
#define First_A First.address
#define First_T First.type
#define First_L First.length
#define Second ArgVector[1]
#define Second_A Second.address
#define Second_T Second.type
#define Second_L Second.length
#define Third ArgVector[2]
#define Third_A Third.address
#define Third_T Third.type
#define Third_L Third.length

#define Apple ArgVector[0]
#define Apple_A Apple.address
#define Apple_T Apple.type
#define Apple_L Apple.length
#define Orange ArgVector[1]
#define Orange_A Orange.address
#define Orange_T Orange.type
#define Orange_L Orange.length

The question is: Is there a way instead of writing all those #defines
for the arguments (First, Second, etc), to write something like:

#define Arg(n) #define Arg ArgVector[n] \
#define Arg##_A Arg.address \
#define Arg##_T Arg.type \
#define Arg##_L Arg.length

and define the arguments like this:

Arg First(0)
Arg Second(1)
Arg Third(2)
Function(One)
....
Arg Apple(0)
Arg Orange(1)
Function(Two)
....

No. The preprocessor is a one-pass utility. It is impossible for it to
#define its own directives.

 

[Dan Pop]

No. The preprocessor is a one-pass utility. It is impossible for it to
#define its own directives.

But it (usually) can be invoked twice, the second invocation processing
the output of the first one. However, I have yet to find a *good*
reason for this approach...

Dan

 

[Thomas Matthews]

Hi all,

I have the following:

/*--- SNIP ---*/

typedef struct Argument_s
{
char *address;
int type;
int length;
} ARGUMENT;

#define Function(F) int F( int ArgCount, ARGUMENT ArgVector[] )

#define First ArgVector[0]
#define First_A First.address
#define First_T First.type
#define First_L First.length
#define Second ArgVector[1]
#define Second_A Second.address
#define Second_T Second.type
#define Second_L Second.length
#define Third ArgVector[2]
#define Third_A Third.address
#define Third_T Third.type
#define Third_L Third.length

Function(One)
{
/* do something with First_A */
/* do something with First_T */
/* do something with First_L */
/* do something with Second_A */
/* do something with Second_T */
/* do something with Second_L */
/* do something with Third_A */
/* do something with Third_T */
/* do something with Third_L */
/* etc etc */
}

#define Apple ArgVector[0]
#define Apple_A Apple.address
#define Apple_T Apple.type
#define Apple_L Apple.length
#define Orange ArgVector[1]
#define Orange_A Orange.address
#define Orange_T Orange.type
#define Orange_L Orange.length

Function(Two)
{
/* do something with Apple_A */
/* do something with Apple_T */
/* do something with Apple_L */
/* do something with Orange_A */
/* do something with Orange_T */
/* do something with Orange_L */
/* etc etc */
}

/*--- SNIP ---*/

The question is: Is there a way instead of writing all those #defines
for the arguments (First, Second, etc), to write something like:

#define Arg(n) #define Arg ArgVector[n] \
#define Arg##_A Arg.address \
#define Arg##_T Arg.type \
#define Arg##_L Arg.length

and define the arguments like this:

Arg First(0)
Arg Second(1)
Arg Third(2)
Function(One)
....
Arg Apple(0)
Arg Orange(1)
Function(Two)
....


Thanks in advance everyone.

Looks like a better design is to have a function that
accesses the structures:
void Set_Arguments(struct Argument_s * arg,
char * address,
int type,
int length)
{
arg->address = address;
arg->type = type;
arg->length = length;
return;
}

One could "Take it up a notch" by using constant identifiers:
#if NO_ENUMERATIONS
#define APPLE 0
#define ORANGE 1
#define WATERMELON 2
#else
enum {APPLE, ORANGE, WATERMELON};
#endif

struct Argument_s fruits[5];

/* ... */
Set_Arguments(&fruit[APPLE], "hello", 1, 25);


--
Thomas Matthews

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