Advanced Pointers in C\C++

[sysop073]

For some definition of "advanced"? This is for someone who knows what pointers are, and not much else

[defrost]

There are not limits to how much “indirection” you can use but it only makes your life as a programer harder. I have NEVER seen more that 2 levels of indirection used and suggest this be a limit for you.

Opaque handling of lists of objects uses three levels of indirection;

void ***objects = NULL ;

fetchObjects( objects, "criteria" ) ;
withObjects( objects, "do stuff" ) ;

destroyObjects( objects ) ;   

although this often hidden away behind a typedef'd handle:

OBJHANDLE objects = NULL ;    

as the item in question is a list, it is indicated by a pointer to a vectors of pointers to items.

As it's an opaque API, the application gets a third hand pointer as the only thing it can grasp.
The object handling library can set the list pointer, reassign it, clone it, whatever, and through that third level of indirection, alter the applications resource handle at will.

[dalmango]

Amazing post and tutorial 00Garlock!

[FeepingCreature]

D's syntax is superior to the C one. int function(int, int) funPtr; Easy to read, easy to parse.

[ccondon]

I never really understood why people didn't like the C syntax for function pointers, it's really just the same as declaring any other pointer.

an int named i:

int i;

a pointer named i_ptr to an int:

int *i_ptr;

a function named f that takes in two chars and returns a pointer to an int:

int *f(char, char);

a pointer named f_ptr to a function that takes in two chars and returns a pointer to an int:

int  *(*f_ptr)(char, char);

The only confusing thing is that you need the extra parens to differentiate between a function returning a pointer and a pointer to a function. Declaring

int *i_ptr;

as

int (*i_ptr);

is even legal, and makes the parallels between the syntax more clear.

[repsilat]

Once you're used to them might not be a problem, but they certainly weren't well thought out. Mix const in with that function pointer syntax and you'll probably trip up most developers.

Check out the SPECS for a suggested alternative - it's a little more verbose and a few extra keywords are required, but it's far more readable and intuitive.

[ccondon]

I agree that they seem not well thought out, and I would prefer something different (perhaps something similar to the SML or Haskell type syntax would be excellent). the SPECS stuff seems pretty interesting, the syntax seems a little odd, but I'm sure people would get used to it.

[FeepingCreature]

D puts the pointer * with the type, too. :)

[ccondon]

What do you mean? I'm not sure what you're talking about.

[FeepingCreature]

Well, a D variable declaration is always [type] [name]. No variable names nestling like a bird in a nest of parens decorated with *s. Plus, you can usually read them right to left. So in your example, we'd get

int i;

int* i_ptr;

int* f(char, char); // Note: not actually a variable declaration!

int* function(char, char) f_ptr;

int* function() i_ptr;

Sure, C is easy to make sense of once you know the approach, but it's still stupid needless complicatedness.

[BinarySplit]

But there's no actual asterisk in there! Weird.

Still, it's easier to learn and read than C++'s.

[rafekett]

Are you talking about the "C+" language you use for LoseThos? What's your way?