Re: why are we not using const?

[Tristan Wibberley <maihem at maihem dot org>]

Manuel LÃpez-IbÃÃez wrote:
> On 27/06/06, Daniel Berlin <dberlin@dberlin.org> wrote:
> > Manuel LÃpez-IbÃÃez wrote:
> > > Apart from its main
> > > purpose, I believed that the use of 'const' helps the compiler to
> > > optimise the code.
> >
> >
> > It generally doesn't, unless you apply const to the underlying type, and
> > not just the pointer.
> >
> > IE you say you have a pointer to a constant piece of memory, not a
> > constant pointer to a piece of memory.
>
> But... tree is a pointer to "union tree_node" , isn't it? perhaps it
> is that "const tree" is not the same as " const union tree_node * " ?
>
> (btw, thanks for taking the time to clarify my doubts...)


typedef union tree_node *tree;
void f(const tree a);

is equivalent to

void f(union tree_node * const a);

ie, it says the pointer is const so there's little point in using it.

typedef union tree_node const *const_tree;
void f(const_tree a);

*would* be meaningful, however.

--
Tristan Wibberley