empty parameterized macro

[John Goche]

Hello,

I would like to know whether there is any difference between
the macro

#define FOO

and the parameterized macro taking no parameters

#define FOO()

What is the purpose of the empty parameter list in the latter?

Thanks,

JG

[Hallvard B Furuseth]

Re: empty parameterized macro

John Goche writes:

I would like to know whether there is any difference between
the macro
>
#define FOO
>
and the parameterized macro taking no parameters
>
#define FOO()

They are called differently. The first is called as just FOO, the
second is called as FOO(). With the second, 'FOO' without () after it
is not expanded at all. If you want to define a constant, you'll
typically define FOO. If you define something which evaluates at
run-time, it looks more informative if you define FOO().

#define FOO one
#define BAR() two
#define BAZ BAR
Now the code
FOO w BAR x BAR() y BAZ() z
expands to
one w BAR x two y two z

--
Hallvard

[aegis]

Re: empty parameterized macro


Hallvard B Furuseth wrote:

John Goche writes:

I would like to know whether there is any difference between
the macro

#define FOO

and the parameterized macro taking no parameters

#define FOO()

>

Is that even allowed under c89?

If so, chapter and verse please.

--
aegis

[Hallvard B Furuseth]

Re: empty parameterized macro

aegis writes:

>Hallvard B Furuseth wrote:

>>John Goche writes:

>>I would like to know whether there is any difference between
>>the macro
>> #define FOO
>>and the parameterized macro taking no parameters
>> #define FOO()

>
Is that even allowed under c89?
If so, chapter and verse please.

Huh? Why not? Ever head of systems where getchar() is a macro?

Look up chapter and verse yourself if you think it's not allowed.
The grammar is something like
# define identifier(iden tifier-list<opt>) replacement-list new-line
Note the <opt(optional ).

--
Hallvard