[TUHS] C declarations.

Bakul Shah bakul at bitblocks.com
Sun May 14 14:24:11 AEST 2017


On Sat, 13 May 2017 21:59:57 EDT Lawrence Stewart <stewart at serissa.com> wrote:
>
> * - But I have never been able to remember the syntax for function pointers.  > I always "man qsort" to refresh my memory.

The way I remember:

given *x[] or *x(), x /sticks/ to the /right/ first. Thus

int *x[];	// x is array of ptr to int
int *x();	// x is a function returning ptr to int

If you don't want a var to stick to its right, separate using
using parentheses.

int (*x)[];	// x is a ptr to array of ints
int (*x)();	// x is a ptr to function returning int
int *(*x)[];	// x is a ptr to array of ptrs to int

This sort of also works for multiple variables in one declaration. Given

int *x, y;	// * /sticks/ to the right (x) first, so not available for y.

Now if they'd allowed parenthesizing the type, as in

(int *)x, y;

we would see that both x & y are of type int *. That would've also allowed
declaring multiple vars in one declaration where the previous rule applies!

(int*)(*f,*g)();

Part of the confusion is * is tacked on at the front while []
& () at the back of a variable.  Someone (Chandy?) had
proposed unifying this syntax but it didn't go anywhere.  I
think the author used @ in a suffix place though I don't
recall any other details.  But if you put the var all the way
to the right and read a declaration right to left, it works:

int*[] x	// x is a array of ptr to ints
int() f		// f is a function returning it
int*()* f	// f is a ptr to function returning ptr to int
int*()* f,g	// f & g are ptrs to function returning ptr to int

This is only slightly weird if you are used to the current syntax
but you can easily retrain yourself.

IMHO, where evolution of C, Scheme and most programming
languages goes wrong is doing evolutionary design by
committee.  Most users grasp what is easier to use vs what is
hard but they don't have the aesthetic sense or imagination or
training to make things simple. And in large groups popularity
or force of personality or some other irrelevant attribute
wins not aesthetics.  Language evolution IMHO must be done by
benevolent dictatorship or a guild of like minded people who
have worked together for a long time!  Go seems to have
adapted that style....


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